chicken pox
🏥 About Chickenpox (Varicella)
Chickenpox (varicella) is an infectious disease caused by the varicella-zoster virus, characterized by fever and widespread blistering rash. The rash begins as red spots, progressing to papules, blisters, and scabs, with different stages of rash coexisting in the same area.
They are common on the face and trunk, and tend to be relatively less common on the limbs.
🟡 Guidelines for attending school/daycare
The School Health and Safety Act states that the criteria for returning to school or kindergarten is "after all rashes have crusted over."
Usually, scabs form about 5 to 7 days after the rash appears, but this varies from person to person. Before scabs form, the infection is highly contagious, so it is necessary to refrain from attending school or daycare.
Ways to spend time at home
Home care is mainly symptomatic treatment.
For fever, use acetaminophen and avoid aspirin.
Keep the skin clean and the nails trimmed to prevent secondary bacterial infections.
Ensure adequate hydration and avoid NSAIDs like ibuprofen, as they may increase the risk of severe bacterial infections.
Symptoms requiring medical attention
If you experience the following symptoms, please seek medical attention immediately.
Redness, swelling, pus, etc. at the rash site, suggesting bacterial infection
If the high fever persists
Difficulty breathing, listlessness, convulsions
Severe headache, vomiting, and confusion
Unsteadiness or difficulty walking
If you can't take in fluids and dehydration is suspected
💉For individuals without immunity who have been in contact with a person with chickenpox, post-exposure vaccination is effective.Vaccination within 3 days of exposure can prevent approximately 80% of cases, and it still provides some protective effect even if administered within 5 days. For those who have already received one dose, a second dose will enhance the protective effect. For individuals who cannot receive the vaccine—such as those with immunodeficiency or pregnant women—immunoglobulin (VariZIG) may be administered within 10 days of exposure.
Literature
• Heininger U, Seward JF. Varicella. Lancet. 2006.
• Dunkle LM, Arvin AM, Whitley RJ, et al. A Controlled Trial of Acyclovir for Chickenpox in Healthy Children. N Engl J Med. 1991.
• American Academy of Pediatrics Committee on Infectious Diseases. The Use of Oral Acyclovir in Otherwise Healthy Children With Varicella. Pediatrics. 1993.
• Ziebold C, von Kries R, Lang R, et al. Severe Complications of Chickenpox in Previously Healthy Children. Pediatrics. 2001.
• Cameron JC, Allan G, Johnston F, et al. Severe Complications of Chickenpox in Hospitalized Children. Arch Dis Child. 2007.
• Chen D, Li Y, Wu Q. Effectiveness of Varicella Vaccine as Post-Exposure Prophylaxis. Hum Vaccin Immunother. 2021.
• Brotons M, Campins M, Méndez L, et al. Effectiveness of Varicella Vaccines as Postexposure Prophylaxis. Pediatr Infect Dis J. 2010.
• Wu QS, Liu JY, Wang X, et al. Effectiveness of the Varicella Vaccine During an Outbreak. Int J Infect Dis. 2018.
• Lin M, Wang Q, Deng P, et al. Varicella Vaccination in a One-Dose-Vaccinated Population. Hum Vaccin Immunother. 2022.
• Frieden TR, Jaffe HW, et al. Updated Recommendations for Use of VariZIG — United States, 2013. MMWR. 2013.
Post-Exposure Prevention for Chickenpox 💉
Post-exposure vaccination
😷Chickenpox is highly contagious, and it is well known that it spreads with a high probability, especially within households.
On the other hand,Infections that can be prevented even after infection (post-exposure)Therefore, it is important to respond appropriately.
Here's how to respond if you come into contact with someone who has chickenpox.
The chickenpox vaccine is not only effective before infection, butEven if vaccinated during the incubation period, it is expected to prevent onset or reduce severity.This has been demonstrated
Therefore, even after coming into contact with someone with chickenpox, it is still possible to receive a preventive vaccination within a certain period of time. Timing of Vaccination and Preventive Effectiveness
⏰ Vaccination timing and preventive effect
The effectiveness of post-exposure vaccines varies depending on the time elapsed before vaccination.
| Vaccination timing | Expected effects |
|---|---|
| Within 3 days (within 72 hours) | About 80-90% prevention of onset |
| Within 36 hours | Approximately 95% efficacy (reported) |
| Within 5 days | Approximately 50-67% prevention rate |
| After the 5th | The effectiveness will decrease, but a milder course of illness is expected. |
Vaccination within 48 hours is considered a sufficiently effective timing.
Furthermore, regarding exposure within families, it has been reported that vaccination reduces the incidence rate and often results in milder symptoms even when infection occurs.
Management of pediatric patients
The response will vary depending on vaccination status.
Not vaccinated, first dose as soon as possible
Received one dose. Will consider a second dose depending on the situation.
Fully vaccinated, additional dose usually not required
If you have received one dose
If you've had one dose, you already have some immunity that can prevent you from getting sick.
If you have recently been vaccinated, it is highly likely that you still have immunity, and there may be no need to get vaccinated immediately.
If time has passed, I will consider a second vaccination.
You can get your second dose if it has been more than 3 months since your last vaccination.
If your child is between 1 and under 3 years old and has not yet completed their two routine vaccinations, they can be vaccinated at public expense.
(Post-exposure vaccination is also covered by public funds if it meets the conditions for regular vaccination.)
If you have been vaccinated twice
If you have completed two doses, you are considered to have immunity and a booster shot is generally not necessary.
It is said that even if it occurs, it often results in mild symptoms.
Supplementary information
By getting a second dose after exposure,
It is reported that the incidence rate has further decreased.
However, whether vaccination is possible and whether vaccination is necessary will be judged separately.
Regarding vaccination intervals
The varicella vaccine is usually completed with two doses. *This interval is based on the standard vaccination schedule and is not a special rule for post-exposure vaccination.
The interval for the second dose is as follows:
| Age | shortest interval |
|---|---|
| child | More than 3 months |
| Since puberty | Over 4 weeks |
In post-exposure prophylaxis, not only the interval between vaccinations, but also
It is important to determine whether an additional dose is necessary, taking into account vaccination history and immune status.
Adult Post-Exposure Prophylaxis
There is less evidence for post-exposure vaccination in adults than in children.
| State | Response |
|---|---|
| Not infected, not vaccinated, vaccination history unknown | Consider vaccination |
| Fully vaccinated | Additional vaccinations are usually not necessary. |
Post-exposure prophylaxis with acyclovir
When the varicella vaccine is unavailable or as an additional preventive measure, prophylaxis with antiviral drugs is also performed.
🔵Effectiveness
It has been reported that acyclovir administration significantly reduces the incidence rate.
・Treatment group: 16% developed
・Control group: 100% developed
Additionally, the frequency of fever has significantly decreased.
🔵 Dosage timing
Starting from 7-10 days after exposure is recommended.
🔵 Usage (Example)
| Target | Dosage | Number of administrations | Period |
|---|---|---|---|
| child | 20mg/kg/dose (max 800mg) | Four times a day | About 7 days |
| Adult | 800mg/dose | 5 times a day | 5-7 days |
🔵 Positioning
In post-exposure prophylaxis,Vaccination is the first choicebetween 27 and 36 weeks of pregnancy.
Acyclovir is considered in the following cases:
・If vaccination is not possible
If more than 5 days have passed since exposure
If you would like additional preventative measures
Summary 🌸
Chickenpox can be prevented even after exposure.
・Most effective within 3 days of vaccination
・Some effect even within 5 days
If you have received one dose, please consider getting a second dose.
・Additional doses are not necessary if you have received two doses.
・If the vaccine cannot be used, acyclovir is also an option.
References
Heininger U, Seward JF. Varicella. The Lancet. 2006;368(9544):1365-1376
•Chen D, et al. Post-exposure prophylaxis for varicella: A systematic review and meta-analysis. Human Vaccines & Immunotherapeutics. 2021
•Macartney K, et al. Vaccines for post-exposure prophylaxis against varicella (chickenpox) in children and adults. Cochrane Database of Systematic Reviews. 2014
•Watson B, et al. Effectiveness of varicella vaccine in clinical practice. Pediatrics. 2000
Wu QS, et al. Effectiveness of varicella vaccine as post-exposure prophylaxis: A meta-analysis. International Journal of Infectious Diseases. 2018
•Lin M, et al. Effectiveness of post-exposure prophylaxis with varicella vaccine: A systematic review. Human Vaccines & Immunotherapeutics. 2022
Wu Q, et al. Post-exposure prophylaxis for varicella: Evidence and recommendations. Clinical Microbiology and Infection. 2019
•Asano Y, et al. Acyclovir prophylaxis of varicella in household contacts. Pediatrics. 1993
Cuerden C, et al. Antiviral prophylaxis for preventing varicella in exposed children. Archives of Disease in Childhood. 2022