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Varicella (chickenpox)

Ask the Experts: Diseases & Vaccines

Varicella (chickenpox)

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Varicella (chickenpox)
Disease Issues For Pregnant Women
Vaccine Recommendations Varicella Zoster Immune Globulin
Scheduling Vaccines Storage and Handling
Contraindications and Precautions
Disease Issues
How serious a disease is varicella?
Prior to the availability of varicella vaccine there were approximately 4 million cases of varicella a year in the U.S. Though usually a mild disease in healthy children, an estimated 150,000 to 200,000 people developed complications, about 11,000 people required hospitalization and 100 people died each year from varicella. Varicella tends to be more severe in adolescents and adults than in young children. The most common complications from varicella include bacterial superinfection of skin lesions, pneumonia, central nervous system involvement, and thrombocytopenia.
How is varicella transmitted and for how long is an infected person contagious?
Varicella spreads from person to person by direct contact or through the air by coughing or sneezing. It is highly contagious. It can also be spread through direct contact with fluid from a blister of a person infected with varicella, or from direct contact with a skin lesion from a person with zoster (shingles). People with varicella are infectious for 4 to 7 days after the appearance of skin lesions and until all lesions are crusted over.
What can be done to protect a patient without evidence of immunity who is exposed to varicella and is at high risk for severe disease and complications?
These patients should receive varicella zoster immune globulin (VZIG). VZIG can modify or prevent clinical varicella disease. In 2006, an investigational VZIG product, VariZIG, became available from the sole authorized U.S. distributor, FFF Enterprises. Details on the use of VZIG may be found in the 2007 varicella ACIP statement (MMWR 2007;56 [RR-4]:29-32). In 2011, the Food and Drug Administration extended the period after exposure in which VZIG may be used from 4 days to 10 days. Details on this change can be found in the MMWR (MMWR 2012;61:212).
What do you give to a child younger than 1 year of age if they were exposed to the chickenpox or zoster virus?
The minimum age for varicella vaccine is 12 months. Vaccination is not recommended for infants younger than 12 months of age even as post-exposure prophylaxis. CDC recommends that a healthy infant (that is, not immunosuppressed, so not a VZIG candidate), should receive no specific treatment or vaccination after exposure to VZV. The child can be treated with acyclovir if chickenpox occurs. Immunosuppressed children should receive VZIG.
Vaccine Recommendations Back to top
Who is recommended to be vaccinated against varicella?
All children, beginning at age 12 months, as well as adults without other evidence of immunity (see next question) should be vaccinated with 2 doses of varicella vaccine. Special consideration should be given to vaccinating adults who (1) have close contact with people at high risk for severe disease (e.g., healthcare workers and family contacts of immunocompromised people), or (2) are at high risk for exposure or transmission (e.g., teachers of young children; child care employees; residents and staff members of institutional settings, including correctional institutions; college students; military personnel; adolescents and adults living in households with children; non-pregnant women of childbearing age; and international travelers).
Does ACIP recommend giving varicella vaccine to infants before age 1 year if they are traveling internationally?
No. ACIP recommends giving a dose of MMR to infants age 6 through 11 months before international travel, but not varicella vaccine. Varicella vaccine is neither approved nor recommended for children younger than age 12 months in any situation.
Can varicella vaccine be used as postexposure prophylaxis for a 9-month-old who was exposed to herpes zoster?
Varicella vaccine is neither approved nor recommended for children younger than age 12 months. Assuming that the child is not immunocompromised, varicella zoster immune globulin (VariZIG, Emergent BioSolutions Inc.) is also not recommended. If the child had a condition which was considered to place the child at greater risk for complications than the general population, then VariZIG could be considered (see the Varicella Immune Globulin section below and www.cdc.gov/mmwr/pdf/wk/mm6228.pdf, page 574).
The Advisory Committee on Immunization Practices (ACIP) does not have a recommendation for acyclovir as varicella postexposure prophylaxis, although the American Academy of Pediatrics does provide some guidance on this issue in the 2015 edition of the Red Book.
What are the criteria for evidence of immunity to varicella?
ACIP considers evidence of immunity to varicella to be
Documentation of 2 doses of vaccine given no earlier than age 12 months, with at least 3 months between doses for children younger than age 13 years, or at least 4 weeks between doses for people age 13 years and older
  U.S.-born before 1980*
  A healthcare provider's diagnosis of varicella or verification of history of varicella disease
  History of herpes zoster, based on healthcare provider diagnosis
  Laboratory evidence of immunity or laboratory confirmation of disease
    *Note: year of birth is not considered as evidence of immunity for healthcare personnel, immunosuppressed people, and pregnant women.
If a healthcare worker does not have a history of varicella vaccination or disease but has had a clinically diagnosed case of shingles, does she or he still need varicella vaccination?
No. A healthcare provider's diagnosis or verification of a history of shingles is acceptable evidence of immunity to varicella. According to ACIP, acceptable evidence of varicella immunity in healthcare personnel includes (1) documentation of 2 doses of varicella vaccine given at least 28 days apart, (2) history of varicella or herpes zoster based on physician diagnosis, (3) laboratory evidence of immunity, or (4) laboratory confirmation of disease.
What should be done if a child or teen inadvertently receives zoster vaccine rather than varicella vaccine?
This is a serious vaccine administration error and procedures should be put in place to prevent this error from happening again. However, the dose of zoster vaccine can be counted as one dose of varicella vaccine. If the error occurred for the first dose the person should receive the second dose of varicella vaccine on schedule.
I have a patient who is 62 years old and is immigrating to the U.S. She received a dose of zoster vaccine 2 months ago. The immigration requirements state she should receive 2 doses of varicella vaccine. Does she need additional varicella vaccine?
To meet the immigration requirements, the dose of zoster vaccine counts as the first dose of the varicella vaccine series. You should give a dose of varicella vaccine now since it has been more than 4 weeks since the dose of zoster vaccine. The varicella vaccine dose may not be needed, but it will not be harmful and will allow your patient to meet the regulatory requirement.
Please review the recommendations for routine second doses of vaccine for everyone, including children.
ACIP recommends that all children receive 2 doses of varicella vaccine routinely. The first dose should be given at age 12 through 15 months and the second dose at age 4 through 6 years. ACIP also recommended "catch-up" vaccination with a second dose for all adolescents and adults who may have missed a second dose. For children ages 12 months through 12 years, the minimum interval between doses is 3 months; for people age 13 years and older, the minimum interval between doses is 4 weeks.
Concerning the recommendation for a second dose of varicella vaccine, does CDC recommend that children who received 1 varicella vaccine dose 10 years ago (when they were preschool age) get a second dose now?
Yes. The current recommendation is for 2 doses regardless of age, for anyone school age and older without evidence of immunity. For everyone whose varicella immunity is based on vaccination, 2 doses of varicella vaccine are recommended.
Why did ACIP revise its recommendations to add a second dose of varicella vaccine for all children?
In the ten years following vaccine licensure in 1995, there was a significant decline in varicella disease, as well as varicella-related hospitalizations and deaths. Although a 1-dose regimen was estimated to be 80% to 85% effective, breakthrough disease was still occurring in highly vaccinated populations. A 2-dose regimen was adopted in 2006 to further reduce the risk of disease among vaccinated people whose numbers would accumulate over time, which could lead to varicella disease later in life when it can be more severe.
Should a child who has had chickenpox prior to the first birthday get the first dose of varicella vaccine at age 1 year?
If the child had confirmed varicella disease or laboratory evidence of prior disease, it is not necessary to vaccinate regardless of age at infection. If there is any doubt that the illness was actually varicella, the child should be vaccinated.
How important is it to vaccinate older children and adults?
It is critical to vaccinate susceptible older children and adults whenever the opportunity arises. With younger children being routinely vaccinated, the chance of being exposed to cases of chickenpox is decreasing. Older children, adolescents, and adults who have not had chickenpox now have a greater chance of remaining susceptible. These older individuals, when they contract chickenpox, are more likely to become seriously ill and have disease complications than younger children.
If an adult or child has not had documented chickenpox but has had shingles, is varicella vaccination recommended?
No. Shingles is caused by varicella zoster virus, the same virus that causes chickenpox. A history of shingles based on a healthcare provider diagnosis is evidence of immunity to chickenpox. A person who has had shingles does not need to be vaccinated against varicella. He/she should still receive zoster vaccine, however, if it is not contraindicated and he/she is age 60 or older.
Can we accept receipt of a single documented dose of zoster vaccine as proof of varicella immunity in a healthcare employee who has no other evidence of immunity?
No. Receipt of zoster vaccine is not proof of prior varicella disease. According to CDC, acceptable evidence of varicella immunity in healthcare personnel includes (1) documentation of 2 doses of varicella vaccine given at least 28 days apart, (2) history of varicella or herpes zoster based on physician diagnosis, (3) laboratory evidence of immunity, or (4) laboratory confirmation of disease. If a healthcare employee has already received a dose of zoster vaccine but has no evidence of immunity to varicella, the zoster dose can be considered the first dose of the 2-dose varicella series.
Should a person who received 2 doses of varicella vaccine be vaccinated with zoster vaccine when they turn 60?
No. CDC does not currently recommend zoster vaccine for people who received 2 doses of varicella vaccine. However, healthcare providers do not need to inquire about varicella vaccination history before administering zoster vaccine because virtually all people currently or soon to be in the recommended age group have not received varicella vaccine. For details, see page 19 of the CDC recommendations Prevention of Herpes Zoster, available at www.cdc.gov/mmwr/PDF/rr/rr5705.pdf.
How safe is varicella vaccine?
Varicella vaccine is very safe. About 20% of vaccine recipients will have minor injection site complaints, such as pain, swelling, or redness. Less than 5% of recipients develop a localized or generalized varicella-like rash 5 to 26 days after vaccination. These rashes have an average of 2 to 5 lesions, and may be maculopapular rather than vesicular. Fever following varicella vaccine is uncommon.
If a child has a very mild case of chickenpox (for example, only 5 to 10 pox), is s/he immune or should s/he be vaccinated?
A mild case of chickenpox produces immunity to varicella as does a moderate or severe case. A child with a reliable history of chickenpox does not need to receive varicella vaccine. However, if there is any doubt that the mild illness really was chickenpox, it is best to vaccinate the child. There is no harm in vaccinating a child who is already immune.
If a child had 1 varicella vaccination and developed a vesicular (chickenpox-like) rash at the vaccination site 7 to 10 days after vaccination, does the patient still need the second dose? What if the rash covered the entire body?
If you believe the child had varicella disease (that is, breakthrough varicella) after the first dose, the child does not need another dose. If you are uncertain whether the child had varicella, the second dose should be administered on schedule. If in doubt, give the second dose. If this was a case of breakthrough varicella, a second dose will not be harmful.
If a child breaks out in 5 to 10 maculopapular spots 2 weeks following varicella vaccination, can s/he go to school?
Transmission of varicella vaccine virus is a rare event, and appears to occur only when the vaccinated person develops a vesicular rash. A maculopapular rash 2 weeks after varicella vaccine may not have been caused by the vaccine. If the rash were caused by the vaccine, the risk of transmission is very small; however, the child should avoid close contact with people who do not have evidence of varicella immunity and who are at high risk of complications of varicella, such as immunocompromised people, until the rash has resolved.
If a vaccinated child gets 5 to 10 vesicular lesions 2 weeks after vaccination, can s/he attend school?
You cannot distinguish a mild case of varicella disease from a rash caused by the vaccine. The child may have been infected with varicella at about the same time s/he was vaccinated. The conservative approach would be to treat the child as if s/he had chickenpox and restrict her/his activities until all the lesions crust.
If a child gets breakthrough varicella infection, about 50 lesions, can s/he go to school?
Breakthrough varicella represents replication of wild varicella virus in a vaccinated person. Although most breakthrough disease is very mild, the child is contagious and activities should be restricted to the same extent as an unvaccinated person with varicella disease.
Can a young child, who was recently vaccinated for chickenpox, spread the vaccine virus to other household members?
Available data suggest that healthy children are unlikely to transmit vaccine virus. Transmission of vaccine virus to a household contact has rarely been documented. It appears that transmission of vaccine occurs mostly, or perhaps even exclusively, when the vaccinated person develops a rash following vaccination.
I understand that varicella vaccine can be used in postexposure settings. How soon after exposure does the vaccine need to be administered?
Varicella vaccine is effective in preventing chickenpox or reducing the severity of the disease if used within 72 hours (3 days), and possibly up to 5 days, after exposure. However, not every exposure to varicella leads to infection, so for future immunity, varicella vaccine should be given, even if more than 5 days have passed since an exposure.
An 8-month-old was erroneously given varicella vaccine. What might the consequences be? What should we do now?
An 8-month-old is likely to have residual passive varicella antibody from his or her mother. The vaccine probably will have no effect, and no action is necessary. The dose should not be counted, and the child should be revaccinated at 12 through 15 months of age.
Does varicella vaccine affect tuberculosis skin test readings in the same way that MMR does?
There is currently no information on the effect of varicella vaccine on reactivity to a tuberculin skin test (TST). Until information is available, it is prudent to apply the same rules to varicella vaccine as are applied to MMR: a TST (i.e., PPD) may be applied before (preferably) or simultaneously with varicella vaccine. If vaccine has been given, delay the TST for at least 4 weeks.
How are we doing as a nation in vaccinating children and adolescents against varicella?
From 2011 to 2014, vaccination with 1 dose of varicella vaccine increased from 26% to 91% among 19–35 month old children, according to the National Immunization Survey (NIS).
Do all states have varicella vaccination requirements before school entry?
As of July 2016, all states require either 1 or 2 doses of varicella vaccine for school entry. Evidence of two doses is required in all but 9 states for children in child care settings, schools, or both. To find out more about laws regarding varicella vaccine requirements, go to IAC's website at www.immunize.org/laws.
How has widespread use of varicella vaccine in children impacted disease?
Substantial reductions in varicella morbidity and mortality have occurred following the licensure of vaccine. Information from three active varicella surveillance areas reported varicella cases had declined by 83% to 93% by 2004, and varicella hospitalizations and deaths declined by more than 90%.
Scheduling Vaccines Back to top
What is the recommended schedule for vaccinating a child? What about adults?
For children, the first dose should be given at age 12 months with a second dose given at age 4 through 6 years. The second dose could be given earlier, if necessary, as long as there is a 3-month interval between doses. All children age 13 years and older as well as adults without evidence of immunity should also have documentation of 2 doses of varicella vaccine, separated by a minimum interval of 4 weeks.
Many children in my practice have had only 1 dose of varicella vaccine. Is there a problem waiting until the 11- to 12-year-old visit to give them the second dose?
Don't delay giving the second dose of varicella vaccine. Give the second dose the next time the child or teen is in your office. The recommendation to routinely give a second dose at age 4 through 6 years is intended to provide improved protection in the 15% to 20% of children who do not adequately respond to the first dose.
What should we do if a child younger than age 13 years was given a second dose with only a 4 week interval?
ACIP recommends that if the interval was at least 28 days it doesn't need to be repeated.
In what circumstances should I obtain a varicella titer after vaccination?
Postvaccination serologic testing is not recommended in any group, including healthcare personnel.
Which of my patients should have varicella serology prior to receiving varicella vaccine?
ACIP does not recommend serologic testing for people younger than age 13 years. At least 90% of adolescents and adults from the U.S. can be expected to be immune to varicella, including those who do not recall having had the disease. As a result, serologic screening may be considered for people age 13 years and older who do not have a history of chickenpox, a strategy that may be cost effective, depending on the cost of the serologic test. However, it is safe to give varicella to people already immune to the disease, so screening is not required under any circumstance.
Should I test women for varicella immunity at their first prenatal visit?
Test pregnant women who lack either (1) documentation of receipt of 2 doses of varicella vaccine or (2) healthcare provider diagnosis or verification of varicella or herpes zoster disease. Women who are not immune should begin the 2-dose vaccination series immediately postpartum.
What is the appropriate lab test to use to determine whether there has been previous chickenpox disease?
Commercially available laboratory tests for varicella antibody are usually based on a technique called EIA (enzyme immunoassay). Though these tests are sufficiently sensitive to detect antibody resulting from varicella zoster virus infection, they are generally not sensitive enough to detect vaccine-induced antibody. The more sensitive assays needed to detect vaccine-induced antibody are not widely available. This is why CDC does not recommend antibody testing after varicella vaccination.
I work in employee health. Several hospital employees have told me they have had chickenpox, but their titers show no antibodies. Should I offer varicella vaccination to them even though they insist they've had the illness?
If you cannot verify a healthcare employee's history of chickenpox, the employee should receive 2 doses of varicella vaccine at least 4 weeks apart. For details, refer to pages 16 and 26 of the CDC recommendations Prevention of Varicella at www.cdc.gov/mmwr/pdf/rr/rr5604.pdf.
A nursing student received 2 valid, documented doses of varicella vaccine. For whatever reason, she subsequently had a titer drawn. The titer was negative. Do you recommend revaccination with 2 doses of varicella vaccine?
No. Documented receipt of 2 doses of varicella vaccine supersedes results of subsequent serologic testing. Most commercially available tests for varicella antibody are not sensitive enough to detect vaccine-induced antibody, which is why CDC does not recommend post-vaccination testing. For more information, see page 24 of ACIP's Immunization of Health-Care Personnel, available at www.cdc.gov/mmwr/pdf/rr/rr6007.pdf.
Contraindications and Precautions Back to top
What are the precautions and contraindications to varicella vaccine?
recent receipt (within the previous 11 months) of antibody-containing blood product (specific interval depends on product)
  moderate or severe acute illness with or without fever
history of a serious reaction (e.g., anaphylaxis) after a previous dose of varicella vaccine or to a varicella vaccine component. For information on vaccine components, refer to the manufacturer's package insert (www.immunize.org/packageinserts) or go to www.cdc.gov/vaccines/pubs/pinkbook/downloads/appendices/B/excipient-table-2.pdf.
  pregnant now or may become pregnant within 1 month
  having any malignant condition, including blood dyscrasia, leukemia, lymphoma of any type, or other malignant neoplasm affecting the bone marrow or lymphatic system
  receiving high-dose systemic immunosuppressive therapy (e.g., two weeks or more of daily receipt of 20 mg or more [or 2 mg/kg body weight or more] of prednisone or equivalent)
  family history of congenital or hereditary immunodeficiency in first-degree relatives (e.g., parents, siblings) unless the immune competence of the potential vaccine recipient has been clinically substantiated or verified by a laboratory
  a child age 1 year or older with CD4+ T-lymphocyte percentages less than 15% or a child, teen or adult age 6 years or older with CD4+ T-lymphocytes count less than 200 cells per microliter
  for combination MMRV only (approved only for children 1 through 12 years of age), primary or acquired immunodeficiency, including immunosuppression associated with AIDS or other clinical manifestations of HIV infections, cellular immunodeficiency, hypogammaglobulinemia, and dysgammaglobulinemia.
What are the recommendations for the use of varicella vaccine in children with HIV or other immunodeficiencies?
ACIP recommends varicella vaccination of children with humoral (but not cellular) immunodeficiencies. In addition, single-antigen varicella vaccine should be considered for HIV-infected children age 1 through 8 years with CD4+ T-lymphocyte percentages greater than or equal to 15% or for children age 9 years and older with CD4+ T-lymphocytes count greater than or equal to 200 cells per microliter. Eligible children should receive 2 doses of varicella vaccine with a 3-month interval between doses. Additional details of these recommendations can be found at www.cdc.gov/mmwr/preview/mmwrhtml/rr5604a1.htm.
We have a 40 lb six-year-old patient who has been taking 15 mg of methotrexate weekly for arthritis for 12 months. Can we give the child MMR and varicella vaccine based on this methotrexate dosage?
Based on the weight and dosage provided (40 lbs and 15 mg/week), the child is currently receiving more than 0.4 mg/kg/week of methotrexate. This meets the Infectious Disease Society of America (IDSA) definition of high-level immunosuppression. Administration of both varicella and MMR vaccines are contraindicated until such time as the methotrexate dosage can be reduced.
The IDSA states that administration of varicella vaccine (but not MMR) can be considered for non-varicella-immune patients treated for chronic inflammatory disease who are receiving long-term low-dose immunosuppression. Low-dose immunosuppression for methotrexate is a dosage of less than 0.4 mg/kg/week. See Table 6 (and associated footnotes): cid.oxfordjournals.org/content/early/2013/11/26/cid.cit684.full.pdf.
If a person develops a rash after receiving varicella vaccination, does he need to be isolated from susceptible people who are either pregnant or immunosuppressed?
Transmission of varicella vaccine virus is rare. However, if a pregnant or immunosuppressed household contact of a vaccinated person is known to be susceptible to varicella, and if the vaccinee develops a rash 7 to 21 days following vaccination, it is prudent that they avoid prolonged close contact with the susceptible person until the rash resolves.
After receiving varicella vaccine, should healthcare personnel avoid contact with immunocompromised patients?
This is not necessary unless the person who was vaccinated develops a rash.
Is there any concern when giving varicella vaccine to a child who lives with a susceptible pregnant woman or an immunocompromised individual?
ACIP recommends varicella vaccine for healthy household contacts of pregnant women and immunosuppressed people. Although there may be a small risk of transmission of varicella vaccine virus to household contacts, the risk is much greater that the susceptible child will be infected with wild-type varicella, which could present a more serious threat to household contacts.
A pediatric surgeon's 12-month-old child received the varicella vaccine and two days later developed a varicella-like rash. The surgeon had chickenpox as a child and had a positive varicella titer several years ago. Is it okay for the surgeon to continue to see patients? Also, is the varicella virus in the rash that develops following vaccination as virulent as the wild-type virus?
Because the surgeon is immune, the child's rash is not a problem and there is no need for the surgeon to restrict activity. In comparing a vaccine rash to wild-type chickenpox infection, transmission is less likely with a vaccine rash and, in general, there are fewer skin lesions.
If a patient is breast-feeding her six-month-old baby, can she receive varicella vaccine without the risk of transmitting the vaccine virus to her baby?
There has been only one published report of mother to child transmission of varicella vaccine virus. If the susceptible woman were to be infected with wild varicella virus, the risk of transmission to the infant would be much higher. So, if the mother is at high risk of exposure to varicella, the benefits of vaccination probably outweigh the risk of transmission to the infant.
A 10-year-old girl came to our immunization clinic, and the nurse noted crusted lesions on her arms and legs. The parent said the child had had chickenpox a week earlier. The girl was not ill, so we vaccinated her. But now I wonder if her recent case of chickenpox might interfere with her immune response to vaccines.
A previous history of chickenpox disease, even recent disease, is not known to interfere with the immune response to different vaccines. To review the true contraindications and precautions to vaccination, consult IAC's "Guide to Contraindications and Precautions to Commonly Used Vaccines" at www.immunize.org/catg.d/p3072a.pdf. Another helpful resource is ACIP's General Recommendations on Immunization. It contains a useful table titled "Conditions commonly misperceived as contraindications to vaccination." The table is available at www.cdc.gov/vaccines/recs/vac-admin/contraindications-misconceptions.htm.
We have a patient who has selective IgA deficiency. We also have patients with selective IgM deficiency. Can MMR or varicella vaccine be administered to these patients?
There is no known risk associated with MMR or varicella vaccination in someone with selective IgA or IgM deficiency. It is possible that the immune response may be weaker, but the vaccines are likely effective.
For Pregnant Women Back to top
What are the recommendations for varicella vaccination before and after pregnancy?
Live varicella vaccine should not be given to a woman who is known to be pregnant or who plans to become pregnant within one month. If a woman who is planning to become pregnant in the future comes in for a visit or an annual exam, her varicella history should be obtained and if indicated, 2 doses of vaccine should be given, spaced 4 to 8 weeks apart. Pregnant women should be assessed for evidence of varicella immunity and if non-immune, should receive the first dose of varicella vaccine following completion of the pregnancy and prior to hospital discharge. A second dose should be given 4 to 8 weeks later.
Can a pregnant healthcare worker with a history of varicella infection care for a patient with varicella? Is it possible for her to have a declining titer, thus making her susceptible to the virus again?
People with a reliable history of varicella can be considered to be immune. A reliable history for healthcare personnel consists of (1) a healthcare provider's diagnosis of varicella or verification of history of varicella disease; (2) a history of herpes zoster, based on healthcare provider diagnosis; or (3) laboratory evidence of immunity or laboratory confirmation of disease. Immunity following disease or vaccination is probably life-long. More than one primary infection with varicella is unusual.
Should all pregnant women have serology screening for varicella?
No. Serologic testing for varicella should be considered only for women who do not have evidence of immunity (reliable history of chickenpox or documented vaccination). Once a person has been found to be seropositive, it is not necessary to test again in the future.
If a woman receives varicella vaccine, how long should she wait before becoming pregnant?
Contrary to the information provided in the vaccine package insert, which states that pregnancy should be avoided for 3 months, the ACIP recommends that a wait of 1 month is sufficient.
If a woman receives varicella vaccine and subsequently finds out that she is pregnant, what should she be told about the risk to the fetus?
To date, no adverse outcomes of pregnancy or in a fetus have been reported among women who inadvertently received varicella vaccine shortly before or during pregnancy. The risk of congenital varicella syndrome following varicella disease is small, so the risk of congenital anomalies following vaccination with live attenuated varicella vaccine is probably very small. In order to clarify this risk, CDC and Merck have established a Varicella Vaccination in Pregnancy registry, similar to that which was established for rubella vaccine inadvertently given during pregnancy. Healthcare providers are encouraged to report such incidents by calling the Merck Pregnancy Registry at (800) 986-8999.
Varicella Zoster Immune Globulin Back to top
A one-month-old infant was exposed for the last 6 days to chickenpox. What should be done to protect the exposed infant, who is too young to vaccinate and past the time for varicella zoster immune globulin (VZIG) administration (96 hours)?
There is no evidence that healthy full-term infants born to women in whom varicella occurs more than 48 hours after delivery are at increased risk for serious complications such as pneumonia or death. VZIG (VariZIG, Emergent) can be given up to 10 days after exposure but is only recommended for newborn infants whose mothers have signs and symptoms of varicella around the time of delivery (5 days before to 2 days after), hospitalized premature infants born at 28 or more weeks of gestation whose mothers do not have evidence of immunity to varicella, or hospitalized premature infants born at less than 28 weeks of gestation or who weigh 1,000 grams or less at birth regardless of their mothers' evidence of immunity to varicella. Assuming this is an infant discharged from the hospital at home, VZIG would not be recommended. Varicella, if it develops, would be managed as for any child.
Storage and Handling Back to top
How should varicella vaccine be stored in my clinic?
Varicella-containing vaccines (varicella, zoster, MMRV) must be stored in a freezer between -58°F and +5°F (-50°C and -15°C) until reconstitution and administration. These vaccines can deteriorate rapidly after they are removed from the freezer. A separate stand-alone freezer should be used to store frozen vaccines that require storage temperatures between -58°F and +5°F (-50°C and -15°C). A storage unit that is frost-free or has an automatic defrost cycle is preferred. Frozen vaccines should not be stored in the freezer compartment of a combination unit because household freezers cannot hold proper storage temperatures for frozen vaccines. This applies to both temporary and long-term storage of frozen vaccines. The diluent should be kept separately in the refrigerator or at room temperature. The vaccine must be administered within 30 minutes of reconstitution.
What happens if you put varicella vaccine in the refrigerator instead of the freezer?
Vaccine will be damaged if not stored according to the manufacturer's instructions. However, it may still be possible to use vaccine that has not been properly stored. Put the affected vaccine vials into the freezer after you have marked them so that they are not confused with the unaffected vials, then call the Merck Vaccine Division at 800-9-VARIVAX right away. Merck will make a recommendation regarding whether the vaccine is still usable, and if so, give you a new expiration date. Do not administer the vaccine until you have consulted with Merck. Similarly, if you have inadvertently left your vaccine at room temperature instead of in the freezer or have experienced a power failure, the same instructions apply.
How can I transport varicella vaccine to a clinic that doesn't have a freezer?
The vaccine manufacturer does not recommend transporting varicella-containing vaccines (varicella, zoster, MMRV). If these vaccines must be transported (for example during an emergency), CDC recommends transport in a portable freezer unit that maintains the temperature between -58°F and +5°F (-50°C and -15°C). Portable freezers may be available for rent in some places. If varicella-containing vaccines must be transported and a portable freezer unit is not available, do NOT use dry ice.
Varicella-containing vaccines may be transported at refrigerator temperature between 36°F and 46°F (2°C and 8°C) for up to 72 continuous hours prior to reconstitution. If varicella-containing vaccines must be transported at refrigerator temperature, follow these steps:
1. Place a calibrated thermometer (preferably with a biosafe glycol-encased thermometer probe) in the container used for transport as close as possible to the vaccines.
2.   Record:
a. The time the vaccines are removed from the storage unit and placed in the container;
b.   The temperature during transport;
c.   The time and temperature at the beginning and end of transport.
3.   According to the vaccine manufacturer, immediately upon arrival at the alternate storage facility:
a. Place the vaccines in the freezer between -58°F and +5°F (-50°C and -15°C) and label "DO NOT USE." Any stand-alone freezer that reliably maintains a temperature between -58°F and +5°F (-50°C and -15°C) is acceptable for storage of varicella-containing vaccines.
b.   Document the time the vaccines are removed from the container and placed in the alternate storage unit.
c.   Note that this is considered a temperature excursion, so contact the manufacturer at 1-800-637-2590 for further guidance.
4. Do not discard vaccines without contacting the manufacturer and/or your immunization program for guidance.
Use of dry ice is not recommended, even for temporary storage or emergency transport. Dry ice may subject varicella-containing vaccines to temperatures colder than -58°F (-50°C).
This page was updated on January 10, 2017.
This page was reviewed on December 14, 2016.
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