If you are in a hurry
- A child with chickenpox must stay out of nursery school until every rash has crusted over (scabbed). If chickenpox is diagnosed after vaccination, the same standard applies
- For a seizure, no response when called, or severe difficulty breathing, call 119 (Japan’s emergency number). If a high fever comes with difficulty breathing, or redness of the skin is spreading, be seen the same day, even at night
- A vaccinated child can still get chickenpox, but it is usually mild. Pregnant women, newborn babies, and people with weakened immunity should ask for advice early
Hello. I am Shunichi Gamo, MD, PhD, a board-certified pulmonologist and the director of Sendai Airport North Clinic.
When your child develops a blister-like rash, you may wonder, “How long do we have to stay out of nursery school or school?” and “Why did this happen when my child was vaccinated?”
Many of you may also have heard from nursery school or school that “chickenpox has appeared,” and are wondering whether your own child will be all right.
Let me give you the conclusion first. For chickenpox (varicella: a rash illness caused by the varicella-zoster virus), a child must stay out of nursery school or school “until every rash has crusted over (scabbed)”[1][2]. If chickenpox is diagnosed after vaccination, the same standard applies[1].
A vaccinated child can still catch chickenpox. However, a Japanese study reports that chickenpox after two doses is often mild[3].
In this article, I explain, as a respiratory specialist, the symptoms and course, how to think about exclusion from nursery school, why chickenpox can occur after vaccination, antiviral medicine, who needs extra care, and when to call 119.
First, a note about our fever clinic on Sundays and national holidays. PCR testing for influenza and COVID (a test that copies the virus’s genetic material in order to detect it) gives results the same day.
From October 4, 2026, we also run the fever clinic on Sundays and national holidays
10:00 to 15:00 (no lunch break). No appointment is needed; you check in on the day. We give you the PCR result the same day. On Sundays and holidays we see fever patients only, and we do not offer general outpatient care or IV drips. We are closed on Sunday, October 25, and from November we are generally open every Sunday and national holiday. Notice: fever clinic on Sundays and national holidays
Shunichi Gamo, MD, PhD
Director, Sendai International Airport North Clinic
Born and raised locally, he attended Yuriage Elementary School and Yuriage Junior High School in Natori City. After graduating from Tohoku University School of Medicine, he worked at Sendai Open Hospital and Kesennuma City Hospital, and then at Tohoku University Hospital. In April 2021, in the middle of the COVID-19 pandemic, he opened Sendai International Airport North Clinic. Holding to a fever clinic that never turns patients away, he cared for well over 20,000 patients with fever in the two years before COVID-19 was moved to Class 5 under Japan’s infectious disease law.
Society memberships and board certifications
Certified Member and Board Certified Fellow, Japanese Society of Internal Medicine
Board Certified Pulmonologist, Japanese Respiratory Society
Board Certified Allergist, Japanese Society of Allergology
Board Certified Specialist, Japanese Society of Anti-Aging Medicine
PhD in Medicine (Tohoku University)
Until when must a child stay out of nursery school with chickenpox?
The exclusion lasts until every rash has crusted over (scabbed)[1].
Article 19 of the Enforcement Regulations of the School Health and Safety Act (the rules on school exclusion) sets the period for chickenpox as “until all of the rash has crusted over”[1]. It adds that this does not apply when the school physician or another doctor judges, based on the child’s condition, that there is no risk of infection[1].
Nurseries are expected to follow this standard and to confirm in advance the guideline for returning to care[2]. The Nursery Guidelines (a manual on infection control in nurseries) also give the return guideline for chickenpox as “all of the rash has crusted over (scabbed)”[2].
| Item | Details |
|---|---|
| Period when it spreads easily | From 1 to 2 days before the rash appears until the rash has crusted over (scabbed)[2] |
| Guideline for returning to nursery school or school | All of the rash has crusted over (scabbed)[2][1] |
| Legal classification | Class 2 infectious disease under the School Health and Safety Act[4] |
The chickenpox rash is typically a mixture of red spots, blisters, and scabs. Once all of it has scabbed over, the child is considered no longer infectious[2].
“The fever is gone” or “the blisters have decreased” can still be too early. A rash that has already scabbed over is not itself a source of infection[5]. The time to wait is while blisters remain.
Before returning, check whether your nursery has its own form
The Nursery Guidelines list chickenpox among the infections for which “a doctor may complete a written opinion form”[2]. However, a written opinion or a return notice is not required everywhere; it depends on what has been agreed in each region[2].
- Every rash has crusted over and no new blisters are appearing
- The fever is gone, and your child can eat and drink and has the usual energy (is well enough to return to group care)[2]
- You have checked whether your nursery requires a written opinion or a return notice
Dr. GamoIt is often hard to tell by eye alone whether a rash has scabbed over. If you are unsure, have your child examined before going back, and we will check together.
For exclusion periods for other illnesses such as influenza, see After influenza: when can my child go back to school or nursery?
What are the symptoms and course of chickenpox?
Chickenpox is an illness with fever and an itchy rash, in which the rash changes from red spots to blisters and then to scabs[4].
The time from infection to symptoms (the incubation period) is about 2 weeks, usually 10 to 21 days[4]. It spreads by airborne transmission (breathing in virus floating in the air), droplet transmission (spray from coughs and sneezes), and contact transmission (touching the blisters and so on)[4].
The rash goes through the following stages, and rashes at different stages are seen mixed together at the same time[5].
| Stage | What the rash looks like |
|---|---|
| Erythema | Red rash |
| Papule | Raised rash |
| Vesicle | Blister |
| Pustule | Blister filled with pus |
| Crust | Scab |
The rash tends to start on the trunk and around the neck and then spread to the face, and some children have no fever[5]. Children may also complain of itching or pain[5].
Chickenpox is mainly a childhood illness, and it is said that more than 90% of cases occur at age 9 or younger[6]. When it becomes serious in children, it is because of complications (other illnesses that occur on top of the main one) such as febrile seizures, pneumonia, and bronchitis[6].
Other complications can include bacterial infections of the skin and the tissue under it, encephalitis, and hepatitis[5]. Bacteria can also cause a secondary infection in the rash[2], so keep your child’s nails short so that the blisters are not scratched open.
Some cases of hand, foot, and mouth disease can be confused with chickenpox[5]. A doctor can tell them apart at the examination. For a related article, see Hand, foot, and mouth disease and herpangina.
Why can my child get chickenpox even after vaccination?
Because the chickenpox vaccine greatly lowers the chance of catching the illness but does not prevent it 100% of the time. Catching chickenpox after vaccination is called breakthrough infection (breakthrough varicella).
A paper that pooled studies from around the world (a meta-analysis: a method that combines the results of several studies) reported vaccine effectiveness as shown in the table below[7].
| Category | Effectiveness |
|---|---|
| One dose, any chickenpox | 81%[7] |
| One dose, moderate to severe chickenpox | 98%[7] |
| Two doses, any chickenpox | 92%[7] |
The protection from one dose also falls off little by little over time. In a study of outbreaks in US schools, the effectiveness of one dose was 93.0% less than 5 years after vaccination, 88.0% at 5 to 9 years, and 81.8% at 10 years or more[8].
In Japan too, it has been reported that while the total number of cases has fallen, the proportion of breakthrough infections, especially after two doses, has gradually risen[3].
Breakthrough infections are often mild
On the other hand, breakthrough infections are often mild. In a US study, the proportion of people with fewer than 50 rash lesions was 24.6% among the unvaccinated, 49.1% after one dose, and 70.0% after two doses[8]. No severe chickenpox was seen in those who had two doses[8].
In a Japanese study too (512 children under 15 with chickenpox confirmed by testing), breakthrough infection after two doses had a shorter period of fever and fewer rash lesions than after one dose[3].
When the symptoms are mild, chickenpox is easy to overlook. The Japanese study also notes that mild breakthrough infections are increasing and that confirming the diagnosis by testing is becoming more important[3]. Even if it is mild, the standard for staying out of nursery school or school is the same once chickenpox is diagnosed[1].
Dr. GamoPlease do not blame yourself with thoughts like “but we had the vaccine.” The vaccine is an important way to prevent severe chickenpox.
When and how many times is the chickenpox vaccine given?
Under the routine vaccination program (vaccinations set by the national government), two doses are given between 12 months and 36 months of age[6]. The eligible period runs from the day before the first birthday to the day before the third birthday[6].
| Dose | Rough timing |
|---|---|
| First dose | Typically between 12 and 15 months of age[6] |
| Second dose | At least 3 months after the first dose. Typically 6 to 12 months after the first dose[6] |
The Ministry of Health, Labour and Welfare states that one dose is thought to prevent severe chickenpox almost 100% of the time, and two doses are thought to prevent the illness including mild cases[6]. People who have already had chickenpox have immunity (the body’s defense system), so they are generally not covered by the routine program[6].
If an unvaccinated child who has never had chickenpox is in contact with someone who has it, an emergency vaccination within 72 hours of the contact may prevent the illness[2]. If a sibling or someone at nursery school has chickenpox, please ask for advice early.
You can check your child’s vaccination record in the maternal and child health handbook. For fever after vaccination, please also see Fever after vaccination.
Is there a medicine for chickenpox? When is antiviral medicine used?
Yes. Antiviral medicines (medicines that slow the virus’s growth) such as acyclovir and valacyclovir are used to treat chickenpox[5].
The Nursery Guidelines state that antiviral medicine is given when there is a possibility of severe illness[2]. Starting treatment early after onset can be expected to improve the clinical symptoms sooner[2].
A review that pooled three trials in healthy children reported that acyclovir shortened the number of days with fever by 1.1 days and reduced the maximum number of rash lesions by 76[9].
Whether to use it is decided by the doctor based on age, underlying conditions, how the rash is appearing, and so on. Please use it exactly as the doctor directs, for the amount and how to take it. If you notice a rash, please ask for advice early.
Easing fever and discomfort: acetaminophen can be used
When the fever is high and your child is uncomfortable, acetaminophen (such as Calonal) can bring the fever down. Follow the instructions of your doctor or pharmacist for the amount and the interval.
A word of caution from the director. Do not give a child with chickenpox any fever medicine that contains aspirin. In chickenpox, taking aspirin is said to be able to cause Reye syndrome (acute encephalopathy: a serious illness in which consciousness becomes abnormal)[5]. Always check with a pharmacist before using an over-the-counter medicine.
Dr. GamoEven if you are only wondering whether to use medicine, it is fine to come in. At the visit, we will explain what suits your child.
Who needs to be especially careful about chickenpox?
Pregnant women, newborn babies, people with weakened immunity, and adults.
| Who | Why extra care is needed |
|---|---|
| Pregnant women | Infection in adults, especially pregnant women, is said to become severe more easily. Infection early in pregnancy can cause congenital varicella syndrome in the baby (a birth defect that comes with low birth weight and underdeveloped arms and legs, among other problems)[5] |
| Newborn babies | If the mother is infected from 5 days before delivery to 2 days after delivery, the baby can develop severe, potentially fatal chickenpox[5] |
| People with weakened immunity | In children with leukemia or those receiving immunosuppressive treatment (treatment that suppresses immunity), the illness can become severe and even lead to death[5] |
| Adults | Chickenpox tends to be more severe than in children and can cause serious complications such as pneumonia and encephalitis[4] |
Chickenpox also spreads through the air[4], so you can catch it just by being in the same room. If any of the following applies to you and you have been in contact with someone who has chickenpox, please talk to a medical facility or your regular doctor early.
- You are pregnant, have never had chickenpox, and have not been vaccinated
- There is a newborn baby at home, and a sibling or another family member has developed a rash
- Someone in the household has leukemia or is receiving treatment that suppresses immunity
- An adult who has never had chickenpox and has not been vaccinated
For fever during pregnancy, please also see Fever during pregnancy: when to see a doctor and which fever medicines are safe.
Signs that mean you should hurry: when to call 119 and when to be seen the same day
If there is a seizure, no response when you call, or severe difficulty breathing, call 119 (Japan’s emergency number) without hesitating. Complications of chickenpox include febrile seizures and pneumonia[6].
Call 119 right away
- There is a seizure (for how to handle a febrile seizure, see the article on febrile seizures)
- Your child does not respond when called, or is limp and does not make eye contact
- There is severe difficulty breathing (the shoulders heave with each breath, or the lips look purplish)
Be seen the same day, even at night or on a holiday
In the following situations, do not wait until morning; go to an emergency department even at night or on a holiday.
- A high fever together with what looks like difficulty breathing, or fast breathing (with severe difficulty breathing, call 119)
- Redness of the skin around the rash is spreading, or the area is swollen and painful (a bacterial secondary infection is suspected)[5]
- Your child is slow to respond when called, is unsteady, or has a severe headache or vomiting (complications such as encephalitis are considered)[5]
- Your child can hardly drink, or is passing less urine
When you go in, to prevent airborne spread[4], phone the medical facility before you arrive, say “this may be chickenpox,” and follow their instructions.
On a night when you cannot tell whether it is serious enough to call 119, you can phone Miyagi Prefecture’s children’s night-time advice line (#8000). Nurses take calls about children, generally under 15 years old, every day from 7:00 p.m. until 8:00 a.m. the next morning[10]. The service gives advice and is not medical treatment[10]. For people aged 15 and over, please use the adult emergency telephone consultation service[10]. If there is a clearly dangerous sign, call 119 without stopping to ask for advice.
Be seen by the next day
- A blister-like rash has appeared, or it may be chickenpox
- A rash has appeared even though your child was vaccinated (a diagnosis is needed even if it is mild)
- You want to have the condition of the scabs checked before returning to nursery school or school
Even when breathing, alertness, and fluid intake are all fine, please be seen early if chickenpox is suspected. Once it is diagnosed, it is easier to plan when your child can return to nursery school.
Frequently asked questions
- My child got chickenpox even after two vaccine doses. When can they go back to nursery school?
-
Chickenpox after two doses is often mild[3]. However, once chickenpox is diagnosed, the return to nursery school or school follows the standard of “until every rash has crusted over”[1]. Even if it is mild, please get a diagnosis and then talk to the nursery.
- The blisters are starting to scab over. Can my child go back to nursery school now?
-
Your child cannot go back until every rash has crusted over[2]. If even one blister remains, it is still time to wait. If you cannot tell by looking, please have your child examined before going back and talk to us.
- My older child has chickenpox. What should I do about the unvaccinated child?
-
If a child has never had chickenpox and is unvaccinated, an emergency vaccination within 72 hours of contact may prevent the illness[2]. Please talk to a medical facility early.
- I was in contact with a child with chickenpox while pregnant.
-
Infection in pregnant women is said to become severe more easily[5]. If you have never had chickenpox and have not been vaccinated, contact your regular obstetric clinic right away.
- The fever from chickenpox is high and my child looks miserable. Can I give fever medicine?
-
Acetaminophen (such as Calonal) can bring the fever down. Use it as your doctor or pharmacist directs. Do not use medicines that contain aspirin because of the risk of Reye syndrome[5].
- My child had a seizure at night. What should I do?
-
If there is a seizure or your child does not respond when called, call 119 without hesitating. If you are unsure, you can ask #8000 for advice[10]. If a high fever comes with difficulty breathing, or redness of the skin is spreading, be seen the same day, even at night.
Summary: return to nursery school only after every rash has crusted over
- A child with chickenpox must stay out of nursery school until every rash has crusted over (scabbed). If chickenpox is diagnosed after vaccination, the same standard applies
- For a seizure, no response when called, or severe difficulty breathing, call 119. If a high fever comes with difficulty breathing, or redness of the skin is spreading, be seen the same day, even at night
- A vaccinated child can still get chickenpox, but it is usually mild. Pregnant women, newborn babies, and people with weakened immunity should ask for advice early
- The routine chickenpox vaccine is given in two doses. If an unvaccinated child who has never had chickenpox is in contact with a patient, ask for advice within 72 hours[6][2]
- Antiviral medicine exists, and starting early matters. Use acetaminophen to bring down the fever, and avoid aspirin
- If you are unsure at night, you can call #8000 about a child. For a clearly dangerous sign, call 119 without asking for advice[10]
With chickenpox, what matters is how you wait until the scabs form and the care you take not to pass it on. When you notice a rash, or when you are unsure about the scabs, please do not hesitate to ask. Leave the medical care to us.
That’s all.
Disclaimer
This article is intended to provide general medical information and does not replace an examination, diagnosis, or treatment by a doctor. The content is based on medical knowledge at the time of publication, but the right course of action differs for each person. If you are worried about symptoms, please consult a medical facility.
References
- Ministry of Education, Culture, Sports, Science and Technology. Enforcement Regulations of the School Health and Safety Act (Ministry of Education Order No. 18 of 1958), Article 19 (Standards for the period of exclusion from attendance). e-Gov Law Search (in Japanese). Accessed October 2026. https://laws.e-gov.go.jp/law/333M50000080018
- Children and Families Agency. Guidelines for Infectious Disease Control in Nurseries (2018 revised edition; partially revised May 2023). Children and Families Agency website (in Japanese). Accessed October 2026. https://www.cfa.go.jp/assets/contents/node/basic_page/field_ref_resources/e4b817c9-5282-4ccc-b0d5-ce15d7b5018c/c60bb9fc/20230720_policies_hoiku_25.pdf
- Hattori F, Higashimoto Y, Miura H, Kawamura Y, Yoshikawa A, Ihira M, et al. Epidemiology and clinical features of breakthrough varicella in the 9 years after universal vaccination began in Japan. Vaccine. 2025 Jun;59:127274. doi:10.1016/j.vaccine.2025.127274 PMID: 40398324
- Japan Institute for Health Security (JIHS). Varicella. Infectious Diseases Information site (in Japanese). Accessed October 2026. https://id-info.jihs.go.jp/infectious-diseases/varicella/index.html
- Japan Pediatric Society, Committee on Immunization and Infectious Disease Control. Explanation of Infectious Diseases to Be Prevented in Schools, Kindergartens, Certified Centers for Early Childhood Education and Care, and Nurseries (April 2025 revised edition). Japan Pediatric Society website (in Japanese). Accessed October 2026. https://www.jpeds.or.jp/uploads/files/20250430_yobo_kansensho.pdf
- Ministry of Health, Labour and Welfare. Varicella Vaccine. Ministry of Health, Labour and Welfare website (in Japanese). Accessed October 2026. https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/kenkou/kekkaku-kansenshou/yobou-sesshu/vaccine/chickenpox/index.html
- Marin M, Marti M, Kambhampati A, Jeram SM, Seward JF. Global varicella vaccine effectiveness: a meta-analysis. Pediatrics. 2016 Mar;137(3):e20153741. doi:10.1542/peds.2015-3741 PMID: 26908671
- Thomas CA, Shwe T, Bixler D, del Rosario M, Grytdal S, Wang C, et al. Two-dose varicella vaccine effectiveness and rash severity in outbreaks of varicella among public school students. Pediatr Infect Dis J. 2014 Nov;33(11):1164-8. doi:10.1097/INF.0000000000000444 PMID: 24911894
- Klassen TP, Hartling L, Wiebe N, Belseck EM. Acyclovir for treating varicella in otherwise healthy children and adolescents. Cochrane Database Syst Rev. 2005 Oct;(4):CD002980. doi:10.1002/14651858.CD002980.pub3 PMID: 16235308
- Miyagi Prefecture. Miyagi Prefecture Children’s Night-time Advice Line Program (#8000). Miyagi Prefecture official website (in Japanese). Accessed October 2026. https://www.pref.miyagi.jp/soshiki/iryou/shouni04.html
▶ Overview of this topic: Fever clinic on Sundays and national holidays (from October 4, 2026, 10:00 to 15:00)
More articles to read when you have a fever
For our Sunday and holiday fever clinic, see Notice: fever clinic on Sundays and national holidays. For how to come in, see About pre-visit questionnaires and same-day check-in for the fever clinic.
