Frequently Asked Questions: Inactivated Influenza Vaccine vs. Nasal Spray (FluMist®)

🌈About the InactivatedInfluenza HA Vaccine

Efficacy and Safety of the Influenza HA Vaccine in Children(Click here for details)

🟠 Number of Doses, Interval, and Timing Recommended Doses
- Children aged 6 months or older but under 3 years: 0.25 mL × 2 doses (2–4 week interval)
- Children aged 3 years or older but under 13 years: 0.5 mL × 2 doses (2–4 week interval)
- Individuals aged 13 years or older: 0.5 mL × 1 dose
※Premature infants are also assessed based on chronological age. If the child turns 3 between doses, the first dose may be 0.25 mL and the second dose 0.5 mL

🟠 Safety
- The incidence rate of adverse reactions tends to increase with age (e.g., 13.58% in children aged 6 months to under 1 year; 49.69% in children aged 3 years to under 6 years)
- The main adverse reactions are swelling at the injection site and fever (fever occurs in 3.67% overall)
- No serious adverse reactions have been reported

🟠 Actual efficacy rate (from case-control study)
・Children under 6 years of age: 33–571 TP3T for a single dose, 41–631 TP3T for two doses (significant for hepatitis B with two doses)
・Children under 3 years of age: 73–831 TP3T per dose (2018/2019–2019/2020)
・During the Type A (H1N1) outbreak: approximately 601 TP3T; during the Type A (H3N2) outbreak: approximately 401 TP3T; Type B: approximately 351 TP3T
・Summary for 2013/2014–2019/2020: Type A total: 441 TP3T; H1N1: 631 TP3T; Type B: 371 TP3T
・Infants aged 6 months to under 1 year: Significant efficacy observed during certain seasons (Type A 36%)
・Effect may be reduced in cases of underlying disease or immunosuppression.
Other points to note
The challenge of antigenicity changes due to egg adaptation is trending toward improvement.
High effectiveness when the prevalent strain and the vaccine strain match
Infants and young children are prone to severe illness, and vaccines are effective to some extent in preventing severe illness and death.
From the perspective of herd immunity, vaccination is also important.
Cannot be administered to infants under 6 months of age, but immunity is expected to be conferred to infants up to approximately 6 months of age after birth through vaccination of pregnant women.

Vaccination for children with febrile seizures
The Japan Society of Child Neurology states that "all current vaccinations can be administered without issue," but emphasizes the need for thorough explanations to parents and guidance on how to respond to fevers and seizures.
Literature
Bonhoeffer J, et al.: Arch Dis Child. 91(11): 929-935, 2006.
2) The European Agency for the Evaluation of Medicinal Products: Harmonisation of requirements for influenza vaccines. CPMP/BWP/214/96, March 1997. https://www.ema.europa.eu/en/documents/scientific-guideline/note-guidance-harmonisation-requirements-influenza-vaccines_en.pdf
3) Pharmaceuticals and Medical Devices Agency: Deliberation Results Report (August 2, 2011). https://www.pmda.go.jp/drugs/2011/P201100137/47003800_16100EZZ01207_A100_1.pdf
4) Grohskopf LA, et al.: MMWR Recomm Rep. 72(2): 1-25, 2023. https://www.cdc.gov/mmwr/volumes/72/rr/pdfs/rr7202a1-H.pdf
Denka Seiken Co., Ltd.: Influenza HA Vaccine "Seiken" Post-Marketing Surveillance Results Announcement. August 2013
6) Fukushima Wakaba, et al.: IASR. Vol. 40 pp.194-195: November 2019. https://www.niid.go.jp/niid/ja/typhi-m/iasr-reference/2471-related-articles/related-articles-477/9236-477r07.html
7) Shinjoh M, et al.: Vaccine. 37(30): 4047-4054, 2019.
8) Fukushima, Wakaba, et al.: IASR. Vol. 42 pp.255-257: November 2021 issue. https://www.niid.go.jp/niid/ja/typhi-m/iasr-reference/2545-related-articles/related-articles-501/10787-501r06.html
9) Shinjoh M, et al.: PLoS One. 10(8): e0136539, 2015.
10) Sugaya N, et al.: Euro Surveill. 21(42): 30377, 2016.
Sugaya N, et al.: Vaccine. 36(8): 1063-1071, 2018.
12) Shinjoh M, et al.: Vaccine. 36(37): 5510-5518, 2018.
Shinjoh M, et al.: PLoS One. 16(3): e0249005, 2021.
14) Shinjoh M, et al.: Vaccine. 40(22): 3018-3026, 2022.
Shinjoh M, et al.: Vaccine. 41(33): 4777-4781, 2023.
16) CDC: MMWR Recomm Rep. 62(RR-07): 1-43, 2013.
Kishida N, et al.: Clin Vaccine Immunol. 19(6): 897-908, 2012.
18) CDC: Preliminary Flu Vaccine Effectiveness (VE) Data for 2023-2024. https://www.cdc.gov/flu/vaccines-work/2023-2024.html
Maurel M, et al.: Euro Surveill. 29(8): 2400089. 2024.
20) National Institute of Infectious Diseases: Antigenic Analysis and Phylogenetic Tree of Circulating Influenza Virus Strains. https://www.niid.go.jp/niid/ja/flu-antigen-phylogeny.html
21) Ministry of Health, Labour and Welfare: Reiwa 5 (2023) Influenza Q&A. https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/kenkou/kekkaku-kansenshou/infulenza/QA2023.html
22) Flannery B, et al.: Pediatrics. 139(5): e20164244, 2017.
23) Takeda S, et al.: J Infect Chemother. 21(4): 238-246, 2015.
24) Expert Committee on Vaccination Guidelines, etc.: Vaccination Guidelines, 2024 Edition. Japan Vaccine Research Center. 2024.
25) Japanese Society of Child Neurology, Supervisor: Guidelines for the Management of Febrile Seizures (Febrile Convulsions) 2023. Diagnosis and Treatment Publishing Co.

🔄Influenza HA Vaccine: Dosage, Interval, and Recommended Timing

Recommended Number of Doses

- Individuals aged 13 to under 65 years, and those aged 65 years or older: typically receive one dose
- Individuals with significantly suppressed immune function may receive two doses at the physician’s discretion


Interval Between Two Doses
- Premature infants are vaccinated based on chronological age.
- Children under 13 years of age typically receive two doses spaced 2 to 4 weeks apart.
•　- A 3 to 4 week interval is preferablefor effective immune acquisition
- The main adverse reactions are swelling at the injection site and fever; no serious adverse reactions have been reported.
- Infants and young children are at high risk of severe influenza, so vaccination is effective in preventing serious illness
- Infants under 6 months of age cannot be vaccinated.Vaccination during pregnancy is expected to confer immunity to the newborn.
- Children with febrile seizures can also be vaccinated.

Interval and Timing for Two-Dose Influenza HA Vaccination (Click to view)(Click here for details)

- According to the American Academy of Pediatrics (AAP),children receiving the influenza HA vaccine for the first timeare recommended to receive two doses,spaced at least 4 weeks apart.
Please note that a 4-day grace period is allowed, and vaccination as early as 25 days later (3 weeks + 4 days) is still considered valid.

• Japan’s Recommendations and Practical Approach

•　In Japan,two doses of the influenza HA vaccine are recommended at an interval of 2 to 4 weeks.Administration 2 weeks after the first dose is widely practiced and accepted in clinical settings.
AAP isa minimum four-week interval to best enhance the immune responseis recommended. Leaving this interval allows the first dose to induce immunity and the second dose to maximize protection (i.e., fully exert the boost effect). As a result, antibody production and clinical preventive efficacy are further enhanced.
- Multiple clinical studies in Japan have shown that vaccination at 2- to 4-week intervals is effective, and there is no evidence of reduced efficacy when the second dose is given after 2 weeks.
- These recommendations are based on Japan-specific immunogenicity data and real-world effectiveness, supporting the validity of the 2-week interval in the Japanese context.
- Japan does not specify a strict “latest possible date” for vaccination.Instead, the primary goal is to complete vaccinationbefore the onset of the influenza season.

1. Recommendations for Prevention and Control of Influenza in Children, 2023–2024. Pediatrics. 2023;152(4):e2023063772. doi:10.1542/peds.2023-063772.
Recommendations for Prevention and Control of Influenza in Children, 2024-2025: Policy Statement. Pediatrics. 2024;154(4):e2024068507. doi:10.1542/peds.2024-068507.
Practice Guideline New Research
3. Effectiveness of Inactivated Influenza Vaccine in Children by Vaccine Dose, 2013-18. Shinjoh M, Sugaya N, Furuichi M, et al.
Vaccine. 2019;37(30):4047-4054. doi:10.1016/j.vaccine.2019.05.090.
4. Effectiveness of Influenza Vaccination Among Children in Satellite Cities of a Metropolitan Area in Tokyo, Japan During the 2014/2015-2018/2019 Season. Matsuda A, Asayama K, Obara T, Yagi N, Ohkubo T.
The Tohoku Journal of Experimental Medicine. 2022;258(1):69-78. doi:10.1620/tjem.2022.J057.
5. Influenza Vaccination in Japanese Children, 2024/25: Effectiveness of Inactivated Vaccine and Limited Use of Newly Introduced Live-Attenuated Vaccine. Shinjoh M, Tamura K, Yamaguchi Y, et al. Vaccine. 2025;61:127429. doi:10.1016/j.vaccine.2025.127429.
6. 2023–2024 Recommendations for Influenza Prevention and Control in Children
Pediatrics. 2023;152(4):e2023063772. doi:10.1542/peds.2023-063772.
7. Policy Statement on Influenza Prevention and Control in Children for 2024–2025
Pediatrics. 2024;154(4):e2024068507. doi:10.1542/peds.2024-068507.
8. Effectiveness of pediatric influenza vaccination by number of doses from 2013 to 2018
Shinjoh M, Sugaya N, Furuichi M, et al.
Vaccine. 2019;37(30):4047–4054. doi:10.1016/j.vaccine.2019.05.090.
9. Effectiveness of pediatric influenza vaccine in satellite cities near Tokyo (2014/15–2018/19)
Matsuda A, Asayama K, Obara T, et al.
Tohoku J Exp Med. 2022;258(1):69–78. doi:10.1620/tjem.2022.J057.
10. Effectiveness of the Influenza Vaccine in Japanese Children for the 2024/25 Season and the Limited Use of the Newly Introduced Live Vaccine
Shinjoh M, Tamura K, Yamaguchi Y, et al.
Vaccine. 2025;61:127429. doi:10.1016/j.vaccine.2025.127429.

Q：Vaccine Spacing and Co-administration

A: Since October 2020, there are no longer any required intervals between the influenza HA vaccine and other vaccines in Japan. - As of July 2022, this also applies to the COVID-19 vaccine, making co-administration with the influenza vaccine possible.

Literature(Click here for details)

1)Ministry of Health, Labour and Welfare: Notice regarding changes to regulations on vaccine administration intervals.
(Accessed as of March 29, 2024)

2)Ministry of Health, Labor and Welfare: COVID-19 Vaccine Q&A;.
(Accessed April 4, 2024)


Onset and Duration of Influenza Vaccine Effectiveness

🟠 Onset of Effectiveness
Immune protection begins approximately 2 weeks after vaccination, with antibody levels reaching protective thresholds around day 14.

🟠 Peak Effectiveness
The vaccine reaches its peak efficacy between 2 to 4 weeks post-vaccination.

🟠 Duration of Protection
In general, effectiveness is maintained for 5 to 6 months. However, the rate of decline may vary depending on virus strain and age.

🟠 Strain-Specific Differences
The A(H3N2) subtype tends to wane more rapidly, with an estimated 7% monthly decline in effectiveness

🟠 Individual Variation
Immune response varies: about half of recipients show a modest antibody response, while others maintain strong and lasting immunity.

🟠 Recommended Timing
To ensure optimal protection, it is recommended to complete vaccination before the start of the influenza season, typically by late October.

This guidance is based on the latest recommendations from the American Academy of Pediatrics (AAP) and the Advisory Committee on Immunization Practices (ACIP).

Literature(Click here for details)

1. Recommendations for Prevention and Control of Influenza in Children, 2023-2024. Pediatrics. 2023;152(4):e2023063773. doi:10.1542/peds.2023-063773.
2. Prevention and Control of Seasonal Influenza With Vaccines: Recommendations of the Advisory Committee on Immunization Practices—United States, 2024–25 Influenza Season. Grohskopf LA, Ferdinands JM, Blanton LH, Broder KR, Loehr J.
MMWR. Recommendations and Reports: Morbidity and Mortality Weekly Report. Recommendations and Reports. 2024;73(5):1-25. doi:10.15585/mmwr.rr7305a1.
3. High-Resolution Antibody Dynamics Following Influenza Vaccination Reveal Predominantly Weak Responses as Well as Infrequent but Durable Immunity Across the 2014–2022 Seasons. Lane A, Quach HQ, Ovsyannikova IG, et al.
Vaccine. 2025;:127677. doi:10.1016/j.vaccine.2025.127677.
4. Intraseason Waning of Influenza Vaccine Protection: Evidence From the US Influenza Vaccine Effectiveness Network, 2011-12 Through 2014-15. Ferdinands JM, Fry AM, Reynolds S, et al.
Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America. 2017;64(5):544-550. doi:10.1093/cid/ciw816.


Q: Side Effects and Management After Influenza HA Vaccination

A: Common reactions include redness, swelling, or pain at the injection site. These usually resolve within 2–3 days. - Occasional systemic symptoms may include fever, fatigue, headache, chills, rash, or hives.
- If the injection site becomes warm or swollen, apply a cool towel or compress to relieve discomfort. A firm lump may remain temporarily, but it typically resolves over time.
- If you experience fever, monitor your condition and consider using cooling methods or antipyretics such as acetaminophen. If you notice unusual symptoms, please consult a healthcare provider promptly.

When Vaccination Should Be Deferred Vaccination is not recommended for individuals who:

- Have a fever of 37.5°C or higher
- Are suffering from a severe acute illness
- Have a history of anaphylaxis caused by previous vaccines
- Developed fever or widespread rash within 2 days of a routine vaccination (excluding voluntary vaccines)

Mild reactions such as redness, swelling, or low-grade fever do not necessarily prevent future vaccination. Please consult your physician to determine whether vaccination is appropriate.

Tips to Reduce Pain and Anxiety During Vaccination

To help ease discomfort and anxiety during vaccination, the following strategies are recommended:

- Avoid using language that may increase fear or anxiety, especially with children or anxious individuals.
- If you have a history of fainting or feeling unwell during injections, consider receiving the vaccine while lying down.
・- Administering the vaccine deeply into the subcutaneous tissue at a 60–90° angle may help reduce local reactions such as swelling. Intramuscular injections are generally associated with fewer local side effects than subcutaneous injections.。

Reporting Suspected Adverse Reactions (Click to view)(Click here for details)

・When adverse reactions are suspected following administration of the influenza HA vaccine, medical institutions report them in accordance with standards established by the national government. The reported data is evaluated by a specialized subcommittee of the Ministry of Health, Labor and Welfare and made public.
During the 2023–2024 season, out of approximately 54 million vaccinations, 57 cases were reported by medical institutions (including 34 severe cases and 5 deaths). Although these are extremely rare cases, appropriate measures are taken in the unlikely event that they occur.
If you have any concerns, please feel free to consult with a doctor or nurse before or after the vaccination. We ask for your understanding and cooperation to ensure a safe and secure vaccination process.

Literature(Click here for details)

1) Vaccination Guidelines Review Committee: Influenza and Pneumococcal Infection (Class B Disease) Vaccination Guidelines 2023 Edition. Vaccination Research Center. 2023.

2) Committee for the Review of Immunization Guidelines, et al.: Immunization Guidelines, 2024 Edition. Public Interest Incorporated Foundation Vaccination Research Center. 2024.

3) Japan Vaccine Industry Association (General Incorporated Association): Vaccine Basics 2023—From Vaccine Manufacturing to Distribution. 2023.

4) The Pharmaceutical Society of Japan: Glossary of Pharmaceutical Terms.

5) The 101st Meeting of the Subcommittee on Adverse Reactions of the Subcommittee on Immunization and Vaccines, Council for Health Science; and the 1st Meeting of the Safety Measures Investigation Committee of the Subcommittee on Safety Measures for Pharmaceuticals, etc., Pharmaceutical Affairs Subcommittee, Pharmaceutical Affairs and Food Sanitation Council, Reiwa 6 (Joint Session). Document 2-26. April 15, 2024. https://www.mhlw.go.jp/content/11120000/001244841.pdf（アクセス2024年4月16日現在）

6) National Institute of Infectious Diseases: App for entering “Reports of Suspected Adverse Reactions Following Vaccination.”. https://www.niid.go.jp/niid/ja/vaccine-j/6366-vaers-app.html（アクセス2024年3月29日現在）

7) Ministry of Health, Labour and Welfare, Health Science Council, Committee on Immunization and Vaccines, Subcommittee on Adverse Reactions. https://www.mhlw.go.jp/stf/shingi/shingi-kousei_284075.html（アクセス2024年3月29日現在）

8) Ministry of Health, Labour and Welfare: Request for reports from physicians, etc., based on the Immunization Act. https://www.mhlw.go.jp/bunya/kenkou/kekkaku-kansenshou20/hukuhannou_houkoku/（アクセス2024年3月29日現在）

Influenza and Tdap Vaccination During Pregnancy (Click to view)(Click here for details)

🟠Influenza Vaccine (Inactivated)

- The inactivated influenza vaccine is safe to administer at any stage of pregnancy.
- The Advisory Committee on Immunization Practices (ACIP)recommends vaccination during early, mid, or late pregnancy,as it plays a vital rolein preventing influenza-related complications in す。both the mother and the baby.

🟠 Tdap Vaccine (Tetanus, Diphtheria, Pertussis)

- The recommended timing for Tdap vaccination isbetween 27 and 36 weeks of pregnancy.
- Receiving the vaccine earlyin this window (around 27–30 weeks)allows for greater transfer of protective antibodies to the baby via the placenta, enhancing protection against pertussis (whooping cough) after birth. - However, Tdap may be administered at any time during pregnancy if needed.
🟠 Why This Timing Matters

- These recommendations are based on scientific evidence showing that maximizing the maternal immune response and enhancing antibody transfer to the fetus provides passive immunity to the newborn.
- This is especially important during the early weeks after birth, when the baby is most vulnerable to infection but not yet eligible for direct vaccination.

References (partial list)
• Razzaghi H, et al. MMWR, 2020;69(39):1391-1397. doi:10.15585/mmwr.mm6939a2.
• Liang JL, et al. MMWR Recommendations and Reports, 2018;67(2):1-44. doi:10.15585/mmwr.rr6702a1.
• Healy CM, et al. JAMA, 2018;320(14):1464-1470. doi:10.1001/jama.2018.14298.
1) Vaccination Guidelines Review Committee: Influenza and Pneumococcal Infection (Class B Disease) Vaccination Guidelines 2023 Edition. Vaccination Research Center. 2023.
2) Committee for the Review of Immunization Guidelines, et al.: Immunization Guidelines, 2024 Edition. Public Interest Incorporated Foundation Vaccination Research Center. 2024.
3) Japan Vaccine Industry Association (General Incorporated Association): Vaccine Basics 2023—From Vaccine Manufacturing to Distribution. 2023.
4) The Pharmaceutical Society of Japan: Glossary of Pharmaceutical Terms.
5)The 101st Meeting of the Subcommittee on Adverse Reactions of the Subcommittee on Immunization and Vaccines of the Council for Health Science, and the First Meeting of the Safety Measures Investigation Committee of the Subcommittee on Safety Measures for Pharmaceuticals, etc., of the Pharmaceutical Affairs Subcommittee of the Pharmaceutical Affairs and Food Sanitation Council for Reiwa 6 (Joint Session). Document 2-26. April 15, 2024. (As of April 16, 2024)
6)National Institute of Infectious Diseases: "Post-Vaccination Adverse Event Suspected Report" Input App. (Accessed as of March 29, 2024)
7)Ministry of Health, Labour and Welfare: Request for reporting by doctors, etc., based on the Immunization Act. Accessed as of March 29, 2024
8)Subcommittee on Adverse Reactions, Health Science Council Committee on Immunization and Vaccines. Accessed on March 29, 2024

Influenza HA Vaccination for Individuals with Allergies

🟠 Individuals with egg allergy or bronchial asthma are generally eligible for vaccination.
🟠 The influenza HA vaccine contains only trace amounts of egg-derived components (typically a few nanograms per milliliter).Therefore, it is considered safe for most people with egg allergy or asthma,and adverse reactions are extremely rare.between 27 and 36 weeks of pregnancy.

Domestic and US Responses (from Vaccination Guidelines)(Click here for details)

•　Contraindications for vaccination:
Those with a history of anaphylaxis due to vaccine ingredients

•　Persons requiring caution with vaccination:
Those with allergies to chicken-derived ingredients such as eggs and chicken meat
Allergic diseases such as asthmaPoor controlIn case of

•　Points to note during vaccination:
Get in good physical condition before vaccination and check your allergy history during the medical questionnaire.
It is recommended to observe patients inside the clinic for 30 minutes after vaccination and to establish an emergency response system.

•　Vaccination for asthma patients:
To prevent asthma exacerbations caused by infections,Influenza vaccination is useful.it is considered that,Can often be administered even during steroid treatment(Please consult your doctor for details)

US Response (from ACIP recommendations)

•　Influenza vaccination is recommended regardless of the presence or absence of an egg allergy.is being done
•　No additional safety measures are necessaryIt is considered that it can be handled in the same way as routine vaccination.
After vaccination15-minute observationis recommended (to reduce risks such as fainting)

Literature

1) Vaccination Guidelines and Other Research Committee: Vaccination Guidelines 2024 Edition. Vaccination Research Center. 2024.
2）Greenhawt M, et al.: Ann Allergy Asthma Immunol. 120（1）: 49-52, 2018.
3) Nagao M, et al.: J Allergy Clin Immunol. 137(3): 861-867, 2016.
4) "Asthma Prevention and Management Guideline 2021" Compilation Committee: Asthma Prevention and Management Guideline 2021. Supervised by the Japanese Society of Allergology, Asthma Guideline Professional Committee. Kyowa Kikaku; 2021.
CDC: MMWR Recomm Rep. 60 (RR-2): 1-60, 2011.
6）Vasileiou E, et al. : Clin Infect Dis. 65（8）: 1388-1395, 2017.
7) GINA: Global Strategy for Asthma Management and Prevention. 2020.
8) Committee on Infectious Diseases: Recommendations for Prevention and Control of Influenza in Children, 2019-2020. Pediatrics. 144(4): e20192478, 2019.

Influenza HA vaccination for pregnant women, nursing mothers, and those planning to become pregnant

Significance and benefits of vaccination

•　Pregnant women are more likely to develop severe illness if they contract influenza, there are concerns about the strain on cardiorespiratory function and the effects on the fetus.
•　Inactivated influenza HA vaccine is highly safe throughout all stages of pregnancy, vaccination is recommended worldwide.
• When pregnant women receive the vaccination,the effect of antibodies transferring to the fetus via the placenta, protecting infants up to 6 months of ageis expected.
• By vaccination of a nursing mother,Preventing maternal infection leads to preventing transmission to the infant.It is considered.
Can be vaccinated even during fertility treatmentand it is considered to have no effect on the fetus after pregnancy is established.

Recommended vaccination schedule

• What are the effects of the vaccine?Lasts from about 2 weeks to about 5 months after vaccinationI will.
• The influenza epidemic in Japancentered around January to MarchBecause ofVaccination is ideal between October and mid-December.between 27 and 36 weeks of pregnancy.

Safety and Precautions

• Symptoms such as fever, swelling, and fatigue as side effects occur with the same frequency regardless of pregnancy.
• There are no reports of increased risks such as miscarriage, premature birth, or malformations.
• Even if a nursing mother receives the vaccination, it will not adversely affect the infant through breast milk.
Even if an infant has an egg allergy, vaccination of the breastfeeding mother is generally not a problem.
• If the mother herself has an egg allergy and avoids consuming eggs, the feasibility of vaccination must be carefully determined.

About preservatives (thimerosal)

• Some vaccines contain trace amounts of thimerosal (ethylmercury) as a preservative, but it is not believed to have any effect on the fetus, and any link to autism has been ruled out.
• For vaccination of pregnant women, it is recommended to choose preservative-free formulations if possible.

Regarding the timing of influenza HA vaccine administration, its effectiveness, and precautions after contracting viral diseases such as shingles or mumps: also, what to do if family members or people around you contract them.

Guidelines for the timing of inactivated influenza vaccination after recovering from a viral disease

•　In mild cases
→ Can be vaccinated as soon as symptoms have resolved

•　In moderate cases
Wait about two weeks after recovery

•　Diseases that cause immunosuppression (e.g., measles)
→ Guideline is 4 weeks or more after healing

•　In the case of shingles
Can be vaccinated if the acute phase has passed and the condition is showing a tendency toward recovery.

What to do if a family member or someone around you becomes infected

• Prior explanation is important to avoid misunderstandings about complications, especially aseptic meningitis after mumps or thrombocytopenic purpura after rubella.
• Determine based on the type of disease and the current outbreak situation
• Vaccination during the incubation period should be administered with caution, as it can easily be mistaken for an adverse reaction

Influenza Vaccination After Recovering from Infection

General Recommendations (Japan) - Vaccination remains effective even after a prior influenza infection.
- It is recommended to wait 1 to 2 weeks after full recovery before receiving the vaccine.
- During the influenza season, early vaccination after recovery is encouraged to maintain protection.
- Since influenza viruses include multiple subtypes, reinfection with a different strain is possible even after one episode.

　🟠 U.S. CDC Guidance - The Centers for Disease Control and Prevention (CDC) reports that vaccination during the recovery phase or incubation period does not reduce vaccine effectiveness or increase the risk of side effects. - Vaccination is not contraindicated for individuals with mild acute illness, those recovering, or those receiving antibiotics. - Even during hospitalization, patients with mild to moderate illness are generally eligible for vaccination.

- The Centers for Disease Control and Prevention (CDC) reports that vaccination during the recovery phase or incubation period does not reduce vaccine effectiveness or increase the risk of side effects
- Vaccination is not contraindicated for individuals with mild acute illness, those recovering, or those receiving antibiotics.
- Even during hospitalization, patients with mild to moderate illness are generally eligible for vaccination.

Literature(Click here for details)

1) Vaccination Guidelines and Other Research Committee: Vaccination Guidelines 2024 Edition. Vaccination Research Center. 2024.
2)CDC: Contraindications and Precautions. General Best Practice Guidelines for Immunization. (Accessed April 12, 2024)
3)Health, Labour and Welfare Bureau for COVID-19 Control, Ministry of Health, Labour and Welfare: Administrative Notice. Regarding the approach to isolation periods after the change in the legal classification of COVID-19 under the Infectious Diseases Control Act (Prior information regarding handling from May 8, 2023). April 14, 2023. Accessed as of March 29, 2024


Q: Please tell me what points to keep in mind when administering the influenza HA vaccine to individuals with underlying conditions such as respiratory, cardiovascular, or renal diseases, and diabetes, or during the perioperative period.(Click here for details)

A: 1 Individuals with underlying medical conditions are strongly recommended to get vaccinated, as they are prone to severe illness if they contract influenza.
2. Except for those for whom vaccination is contraindicated, it is generally safe to receive, but caution is required in differentiating between side effects and the effects of underlying medical conditions or treatments.
3. In patients with chronic respiratory diseases, serious side effects are rare, but post-vaccination observation is necessary given the risks of asthma attacks and interstitial pneumonia.
4 Patients with cardiovascular disease should be careful of blood pressure fluctuations and vasovagal reactions due to injection site pain, and those taking anticoagulants should also consider bleeding at the injection site.
5. There are also reports that influenza vaccination reduces the risk of cardiovascular events.
6. Active vaccination is recommended for patients with kidney disease, especially dialysis patients, because they have a high risk of infection and mortality rate.
7. Patients with liver disease can receive the vaccination if their condition is stable, and caution should be exercised regarding injection site bleeding if thrombocytopenia is present.
8. Although immune responses are slightly reduced in patients with autoimmune diseases and those in an immunosuppressed state, safety has been reported.
9. Care must be taken to differentiate vaccine side effects in patients with cerebrovascular disorders or central nervous system diseases. For epilepsy patients, vaccination should be administered when their condition is stable, and it is important to explain seizure prevention measures.
10 Although slightly less effective in diabetic patients, it is effective, contributes to reducing the risk of hospitalization and death, and annual vaccination is recommended.
Perioperative vaccination is generally avoided because it makes symptom differentiation difficult, but it is considered on an individual basis, and for organ transplant patients, the timing of vaccination is determined according to their condition.
12. After recovering from COVID-19 symptoms and becoming non-infectious, vaccination is possible, and simultaneous vaccination is not a problem.
Vaccination outside of medical facilities is possible at home or elsewhere as long as safety management is in place, and careful medical interviews and observation are important for immunocompromised patients.
Based on these factors, under appropriate management, influenza HA vaccination for patients with underlying medical conditions is an important infection prevention measure.

Literature(Click here for details)

1)Ministry of Health, Labour and Welfare: FY2023 Influenza Q&A. (Accessed April 9, 2024)
2)CDC: Who Should and Who Should NOT get a Flu Vaccine. Accessed April 9, 2024
3)The 101st Meeting of the Subcommittee on Adverse Reactions of the Subcommittee on Immunization and Vaccines of the Council for Health Science, and the First Meeting of the Safety Measures Investigation Committee of the Subcommittee on Safety Measures for Pharmaceuticals, etc., of the Pharmaceutical Affairs Subcommittee of the Pharmaceutical Affairs and Food Sanitation Council for Reiwa 6 (Joint Session). Document 2-26. April 15, 2024. (As of April 16, 2024)
4) Pesek R, et al.: Allergy. 66(1): 25-31, 2011.
5) Udell JA, et al.: JAMA. 310(16): 1711-1720, 2013.
6) Japanese Society of Nephrology: Evidence-based clinical practice guideline for CKD 2023. June 2023.
7) Japanese Association of Dialysis Physicians: Guidelines for Standard Dialysis Operations and Infection Prevention in Dialysis Facilities (6th Revised Edition). December 2023.
8) Song JY, et al.: J Clin Virol. 39(3): 159-163, 2007.
9) Huang Y, et al.: Curr Med Res Opin. 33(10): 1901-1908, 2017.
10) Westra J, et al.: Nat Rev Rheumatol. 11(3): 135-145, 2015.
11) Lu CC, et al.: Vaccine. 29(3): 444-450, 2011.
12) Japanese Society for AIDS Research: Vaccination Guidelines for People Living with HIV. July 2023.
13) Japanese Society for Pediatric Infectious Diseases, supervisor: Guidelines for Vaccination in Immunocompromised Patients 2024. 2024.
14) Vaccination Guidelines Review Committee: Vaccination Guidelines 2024 Edition. Vaccination Research Center; 2024.
15) Casper C, et al.: Blood. 115(7): 1331-1342, 2010.
16) Lau D, et al.: Thorax. 68(7): 658–663, 2013.
17) Vamos EP, et al.: CMAJ. 188 (14): E342-E351, 2016.
18) Japan Diabetes Society, ed.: Treatment Guide for Diabetes 2019. Nankodo, 2019.
19) Nobuhiko Okabe, Keiko Taya, Hajime Kamiya: Q&A on Vaccinations 2023. Q9 p.46-47, Japan Vaccine Industry Association. 2023.
20) Japanese Society for Hematopoietic and Immune Cell Therapy: Guidelines for Hematopoietic Cell Transplantation: Vaccination (4th Edition). December 2023.
21) Tartof SY, et al.: Ann Intern Med. 164(9): 593-599, 2016.
22)Japan Respiratory Society (General Incorporated Association) COVID-19 FAQ Hub. (Accessed April 9, 2024)
23) Japan Pediatric Society, Japan Society for Pediatric Infectious Diseases, and Japan Association for Ambulatory Pediatrics, Pediatric COVID-19 Joint Working Group: Guidelines for the Clinical Management of Coronavirus Disease 2019 (COVID-19) in Pediatric Outpatient Practice, 2nd ed. September 29, 2021.
24)Ministry of Health, Labor and Welfare: COVID-19 Vaccine Q&A;. (Accessed April 9, 2024)
25)Ministry of Health, Labour and Welfare: Guidelines for Routine Vaccination Implementation.
26) Ministry of Health, Labour and Welfare Notification: Isei-hatsu No. 0331 No. 68, Ken-hatsu No. 0331 No. 28. March 31, 2015.
27）Caldera F, et al.: Vaccine. 39: A15-A23, 2021.

Q:What is the effectiveness of influenza vaccination in healthy adults under the age of 65? (Click to view)(Click here for details)

A:　On the Efficacy of the Influenza HA Vaccine

• The influenza HA vaccine has been shown to have a relatively high preventive effect for healthy adults under 65 years of age, and vaccination is recommended.
• If the vaccine strain and the circulating strain match,Approximately 60% effectiveness in preventing the onset of the diseaseis expected.
• This is particularly important for caregivers of individuals at high risk of severe illness and for healthcare workers.

• However, because influenza viruses mutate every year, their effectiveness decreases if the antigenicity of the vaccine strain and the circulating strain do not match.

Still, vaccination can often reduce the risk of severe illness and hospitalization,Annual vaccination is recommended for everyone aged 6 months and older who is eligible.It is being done.

Reference 1)Ministry of Health, Labour and Welfare FY2023 Influenza Q&AAccessed April 4, 2024
2)Demicheli V, et al.: Cochrane Database Syst Rev. 2(2):1-255, 2018
3) CDC: Who needs a flu vaccine (Retrieved April 4, 2024)
4)CDC: CDC seasonal flu vaccine effectiveness studies (Retrieved April 4, 2024)
5)Ministry of Health, Labour and Welfare Infectious Disease Control Manual for Elderly Care Facilities Revised Edition 2019 (Retrieved April 4, 2024)
6) Children and Families Agency, Nursery School Infectious Disease Control Guidelines 2018 (Retrieved April 4, 2024)
7）Baumgartner EA, et al.: J Infect Dis.206（6）:838-846,2012 8）Vaccination Guidelines and Other Issues Review Committee, Influenza and Pneumococcal Vaccination Guidelines, 2023 Edition, 2023
9)CDC: Guidance for Cruise Ships on Influenza-like Illness (ILI) Management
10) WHO: Influenza surveillance outputs (Accessed: May 13, 2024)
11)National Institute of Infectious Diseases Influenza Patient Incidence Status (Retrieved May 13, 2024)
12)Japan National Tourism Organization JNTO Annual Number of Foreign Visitors to Japan(Accessed May 13, 2024)
13)Japan Vaccine Society 2022-23 Season Statement on Seasonal Influenza Vaccination (Retrieved April 4, 2024)

🧬About the Influenza Nasal Live Vaccine FluMist®

Eligibility and contraindications for FluMist® (live attenuated influenza vaccine: LAIV)

* Special notes regarding children with a history of asthma, wheezing, allergic rhinitis, or food allergies

Eligible persons:

•　Ages 2 to 18 (under 19)
• Health condition: Individuals without severe asthma or immunodeficiency
• Non-pregnant individuals (pregnant women and those who may be pregnant are excluded)

People who need to be cautious about vaccination

• Individuals with severe rhinitis or nasal congestion (efficacy may be reduced)
• Those with a gelatin allergy
• People undergoing immunosuppressive therapy or who are immunocompromised
• Those who are pregnant or may be pregnant
• People with severe asthma who have recently had an attack
• Kawasaki disease patients taking aspirin
• Those who have daily contact with severely immunocompromised individuals
• In the United States, FluMist®Aged 2 to 49is approved for healthy non-pregnant individuals, but in Japan it is for those aged 2 to 18 (under 19)

Taboo:

Children who meet the following conditions cannot receive FluMist®.

• Children under 2 years of age (due to the high risk of hospitalization and wheezing)
• Children aged 2 to 4 years with a history of wheezing or asthma within the past 12 months
• Children with severe asthma or current wheezing
• Children who have had a severe allergic reaction, such as anaphylaxis, to any component of past influenza vaccines or FluMist
• Children with a gelatin allergy (inactivated vaccine or recombinant vaccine is used depending on age)
• Children during pregnancy (at the time pregnancy is discovered)
• Close contacts and caregivers of severely immunocompromised individuals
• Children who have recently taken influenza antiviral drugs (cannot be vaccinated for a certain period)

Notes:

•　Children aged 5 years and older with asthma or chronic conditions (such as pulmonary, cardiac, renal, hepatic, neurological, hematological, or metabolic disorders), the inactivated influenza vaccine is generally recommended over FluMist®.
•　Guillain-Barré syndromeCaution is required with all influenza vaccines if there is a history of this within 6 weeks of the previous influenza vaccination.
• If you have a moderate to severe acute illness (including COVID-19), postpone vaccination until symptoms improve. Mild symptoms are not a contraindication.
allergic rhinitis and mild upper respiratory symptomsChildren with [condition missing in source] are not at high risk for adverse events from FluMist® vaccination and it is not contraindicated.
• Children with food allergies (including egg allergy) can safely receive all influenza vaccines, including FluMist®.
• Vaccination is recommended under medical supervision for individuals with a severe egg allergy (anaphylaxis), but overall, the risk is not high.

🔺 Administration of FluMist before and after taking anti-influenza drugs

When receiving the live attenuated influenza vaccine (FluMist), the waiting period before vaccination varies depending on the history of anti-influenza drug use.

• When using oseltamivir (Tamiflu) or zanamivir (Relenza), from the final administration48 hours、
With peramivir (Rapiacta)For 5 days,
Regarding baloxavir marboxil (Xofluza)17 daysIt needs to be opened.

• This is because if administered during these periods, antiviral drugs may hinder the replication of the vaccine virus and weaken the effectiveness of the vaccine.
If the excretion of the drug is delayed due to renal dysfunction or other reasons, it is recommended to further extend the interval.

• If you are taking antiviral medication before vaccination, please allow sufficient time to pass after the above period before receiving FluMist®.

•　If antiviral drugs are used within two weeks after vaccination, sufficient effects may not be obtained, so re-vaccination with the inactivated influenza vaccine (injection type) is recommended.

•　FluMist® is a live vaccine that establishes immunity as the virus multiplies within the body. Because antiviral drugs hinder this replication, the use of antiviral drugs during the administration period or within two weeks after vaccination may reduce the vaccine's effectiveness.

• Inactivated vaccines do not involve viral replication, so they are not affected by antiviral drugs, and reliable immune effects can be expected. Please consult with a physician regarding the timing of re-vaccination, and decide based on your physical condition and medication status.

* These are set based on the drug's duration of action and elimination rate in the body. If there is renal impairment or the like, the period may be longer.

• Regarding the period during which rapid influenza diagnosis (antigen detection) tests positive after vaccination

Impact on testing and virus shedding after FluMist (nasal live vaccine) administration

Flumist® is a live vaccine that builds immunity by allowing a weakened virus to multiply slightly inside the nose. Therefore, for a while after vaccination, influenza tests may yield results close to "positive." Here are some points we would like parents to know.

An influenza test may sometimes test positive after vaccination.

If you develop a fever or nasal symptoms after vaccination and undergo a rapid influenza test at a medical facility (a test where a swab is inserted into the nose), you may test positive because the test reacts to the vaccine virus.

  • mainlyWithin one week after vaccinationtend to be positive, and after that, they gradually decrease.
  • Most positive results on rapid antigen tests areWithin 7 days after vaccinationAlmost no cases have been reported where it was detected and turned positive after the 12th day.
  • With more precise tests (such as PCR tests), rarelyabout 3 weeksUntil then, trace amounts of the virus may be detected. However, the viral load during this period is extremely small and does not affect your health.

For this reason, if symptoms such as a fever occur within 1 to 2 weeks after vaccination, it can sometimes be difficult to determine whether they are a "vaccine reaction" or an "actual influenza infection." If you have any concerning symptoms, please consult a physician and inform them that you have received the vaccination.

Can it be transmitted to people around you?

Because FluMist® is a live vaccine, there is a very small possibility that the virus multiplying in the vaccinated child's nose could be transmitted to people around them. However, according to actual research results, the probability of someone who came into contact with a vaccinated child becoming infected with the vaccine virus isLow, at around 1–21 TP3Toften there are no symptoms either.

  • There are no restrictions on normal daily life (living together, hugging, taking children to nursery school, etc.) with your family, siblings, healthy pregnant women, or infants.
  • What you need to be careful about is,Close contact for about one week after vaccination with individuals whose immune systems are severely suppressed due to a serious illness (such as those who have undergone a bone marrow transplant), if applicable, please consult your doctor before vaccination.

Literature(Click here for details)

1. Recommendations for Prevention and Control of Influenza in Children, 2023-2024. Pediatrics. 2023;152(4):e2023063773. doi:10.1542/peds.2023-063773.
2. Recommendations for Prevention and Control of Influenza in Children, 2022-2023. Pediatrics. 2022;150(4):e2022059275. doi:10.1542/peds.2022-059275.
3. Recommendations for Prevention and Control of Influenza in Children, 2024-2025: Policy Statement. Pediatrics. 2024;154(4):e2024068507. doi:10.1542/peds.2024-068507.
4． Recommendations for Prevention and Control of Influenza in Children, 2019-2020. Pediatrics. 2019;144(4):e20192478. doi:10.1542/peds.2019-2478.
5. Safety of Live Attenuated Influenza Vaccine in Young People With Egg Allergy: Multicentre Prospective Cohort Study. Turner PJ, Southern J, Andrews NJ, Miller E, Erlewyn-Lajeunesse M.
6. Safety of Live Attenuated Influenza Vaccine in Atopic Children With Egg Allergy. Turner PJ, Southern J, Andrews NJ, Miller E, Erlewyn-Lajeunesse M. The Journal of Allergy and Clinical Immunology. 2015;136(2):376-81. doi:10.1016/j.jaci.2014.12.1925.
7. Administration of Influenza Vaccines to Egg Allergic Recipients: A Practice Parameter Update 2017. Greenhawt M, Turner PJ, Kelso JM.
8．Annals of Allergy, Asthma & Immunology : Official Publication of the American College of Allergy, Asthma, & Immunology. 2018;120(1):49-52. doi:10.1016/j.anai.2017.10.020.
9. The Adverse Reactions to Vaccines Practice Parameter 10 Years on-What Have We Learned?. Kelso JM. Annals of Allergy, Asthma & Immunology : Official Publication of the American College of Allergy, Asthma, & Immunology. 2022;129(1):35-39. doi:10.1016/j.anai.2022.01.026.1.
10.Prevention and Control of Seasonal Influenza With Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2022-23 Influenza Season.Grohskopf LA, Blanton LH, Ferdinands JM, et al.

11．MMWR. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports. 2022;71(1):1-28. doi:10.15585/mmwr.rr7101a1. Copyright License: CC0
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13.Recommendations for Prevention and Control of Influenza in Children, 2023-2024.Pediatrics. 2023;152(4):e2023063772. doi:10.1542/peds.2023-063772.
14.Prevention and Control of Seasonal Influenza With Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2024-25 Influenza Season.Grohskopf LA, Ferdinands JM, Blanton LH, Broder KR, Loehr J.
15. MMWR. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports. 2024;73(5):1-25. doi:10.15585/mmwr.rr7305a1.
16.Detection of Influenza Antigen With Rapid Antibody-Based Tests After Intranasal Influenza Vaccination (FluMist).Ali T, Scott N, Kallas W, et al.
Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2004;38(5):760-2. doi:10.1086/382887.
17. FluMist. FDA Drug Label.Food and Drug Administration (DailyMed).
18.Recommendations for Prevention and Control of Influenza in Children, 2024-2025: Policy Statement.Pediatrics. 2024;154(4):e2024068507. doi:10.1542/peds.2024-068507. Practice Guideline
19.Prevention and Control of Seasonal Influenza With Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2024-25 Influenza Season.Grohskopf LA, Ferdinands JM, Blanton LH, Broder KR, Loehr J.
20 MMWR. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports. 2024;73(5):1-25. doi:10.15585/mmwr.rr7305a1. Practice Guideline20
21.Recommendations for Prevention and Control of Influenza in Children, 2023-2024.Pediatrics. 2023;152(4):e2023063772. doi:10.1542/peds.2023-063772.Pediatrics. 2023;152(4):e2023063773. doi:10.1542/peds.2023-063773.