Guidance

The safety of chickenpox (Varilrix® and Varivax®) and shingles (Shingrix®) vaccines when given in pregnancy

Updated 20 January 2025

Introduction

Both chickenpox and shingles are caused by the same virus called varicella-zoster. You can only get shingles if you have previously had chickenpox (or, rarely, shingles can arise after chickenpox vaccine). After having chickenpox as a child, the varicella-zoster virus stays in your body, and can become active again many years later to cause shingles. Shingles is more common in older adults and those with weakened immunity. For the effects of chicken pox or shingles disease in pregnancy see Natural chickenpox or shingles infection in pregnancy section.

Pregnant women who have received chickenpox vaccine

There is no specific safety concern, either for the mother or the baby, when chickenpox vaccine (Varilrix® or Varivax®)  is given in, or shortly before pregnancy, and no cases of fetal varicella syndrome have been causally linked to chickenpox vaccine (1). Women who have been immunised with chickenpox vaccine in pregnancy can therefore be immediately reassured.

Pregnant women who have received Shingrix® vaccine

Women who have received Shingrix® shingles vaccine should be reassured that this is not a live vaccine and cannot infect them or their baby and there is no known risk associated with this type of vaccine when given at any time in in pregnancy.

The safety of chicken pox and shingles vaccines given in pregnancy or shortly before conception

Women should be reassured that the weakened varicella-zoster virus in chickenpox and earlier shingles vaccines has not been linked to specific problems in babies born to women who have received vaccines containing this virus whilst pregnant.

Chickenpox and shingles vaccines are not recommended in pregnancy as a matter of caution. Most women in the UK will already be immune to varicella-zoster virus. If women are immune when they receive chickenpox or shingles vaccine the vaccine will simply boost their existing antibodies against varicella zoster virus, as it would if they came across the natural diseases. No specific risk has been associated with the weakened varicella-zoster virus used in chicken pox or earlier shingles vaccines when women have been immunised during pregnancy or shortly before becoming pregnant. The shingles vaccine in current use is not a live vaccine and so does not contain the weakened varicella-zoster virus.

A Varicella-Zoster Virus-Containing Vaccines Pregnancy Registry was established in the USA in 1995 to monitor the outcomes of pregnant women who were inadvertently immunised with varicella-zoster virus-containing vaccines 3 months before or any time during pregnancy. No cases of fetal varicella syndrome (see section on fetal varicella syndrome) were detected and the overall rate of birth defects in the infants of women who received these vaccines and were reported to the registry was similar to the expected rate in the rest of the population over the 19 years that the registry was running (1, 2, 3).

Over this 19-year period, there were 966 reports of women who inadvertently received chickenpox vaccine up to 3 months before pregnancy or at any time during pregnancy reported before the outcome of pregnancy was known (prospective reports), where pregnancy outcomes were available for analysis, and considered complete (1). No conditions consistent with fetal varicella syndrome (see section on fetal varicella syndrome) were reported. This included 164 prospective reports of babies born to women who were not immune to chickenpox when vaccinated, with 104 of these babies exposed during the high-risk period for congenital varicella syndrome (first and second trimester of pregnancy.

The UK Vaccine in Pregnancy surveillance programme

All exposures to any chickenpox or shingles vaccine, from 90 days before conception to any time in pregnancy should be reported to the UK Vaccine in Pregnancy surveillance programme. This is run by the Immunisation and Vaccine Preventable Diseases Division at the UK Health Security Agency (UKHSA; formerly known as Public Health England) (4). The objectives of the UK Vaccine in Pregnancy surveillance are to compile additional information on women who are immunised with specified vaccines whilst pregnant to monitor the safety of such exposures. This data will be used to help better inform pregnant women who are inadvertently immunised, their families and health professionals who are responsible for their care.

Natural chickenpox or shingles infection in pregnancy

When a woman has natural chickenpox infection in pregnancy both the woman and her baby may be affected. On rare occasions this can lead to the baby being born with developmental abnormalities: this is called fetal varicella syndrome (see section on fetal varicella syndrome).

If a woman is infected with chickenpox whilst pregnant there are risks to both her and the baby. Chickenpox can cause severe maternal disease, and 10% to 20% of pregnant women infected later in pregnancy develop varicella pneumonia, hepatitis and encephalitis. The incidence of varicella pneumonia in pregnancy has previously been reported at 10 to 14% based on a small case series (5). In a more recent study of almost 1,000 pregnant patients with chickenpox, the rate of pneumonia was 2.5% with no maternal deaths, reflecting improved medical care and use of acyclovir, an antiviral medicine (6). Newborn babies whose mothers develop varicella rash from 5 days before to 2 days after delivery are at risk of neonatal varicella, and around 30% of these babies die. Infection of the foetus may result in:

• stillbirth
• shingles during infancy or early childhood
• fetal varicella syndrome

In contrast, the vaccines contain a weakened strain of the varicella-zoster virus that will protect against the natural infection and has not been found to cause these problems.

Fetal varicella syndrome

Babies born to mothers who were infected with varicella-zoster virus up to week 28 of their pregnancy are at risk for a very serious condition known as fetal varicella syndrome.

This is characterised by:

• low birthweight
• scarring of the skin
• withered limbs
• small head
• cataracts
• other problems

In a prospective study conducted in Europe from 1980 to 1993 involving nearly 1,400 mothers who had varicella infection during pregnancy, the highest risk (2%) for fetal varicella syndrome was observed when maternal infection occurred during 13 to 20 weeks gestation. Before 13 weeks the risk was estimated to be around 1%.

In contrast, the vaccines contain a weakened strain of the varicella-zoster virus that protects against this infection and has not been found to cause these problems.

References

1. Willis ED, Marko AM, Rasmussen SA, McGee M, Broder KR, Marin M. Merck/Centers for Disease Control and Prevention ‘Varicella Vaccine Pregnancy Registry: 19-year summary of data from inception through closure, 1995 to 2013’ Journal of Infectious Disease: 21 October 2022, volume 226, issue supplement 4, pages S441 to S449

2. Wilson E, Goss M, Marin M and others. ‘Varicella vaccine exposure during pregnancy: data from the first 10 years of the pregnancy registry’ Journal of Infectious Disease: March 2008, volume 197, issue supplement 2, pages S178 to S184

3. Marin M, Willis ED, Marko A, Rasmussen SA, Bialek SR, Dana A; Centers for Disease Control and Prevention (CDC). ‘Closure of varicella-zoster virus-containing vaccines pregnancy registry, United States, 2013’ Morbidity and Mortality Weekly Report (MMWR): 22 August 2014, volume 63, issue 33, pages 732 to 733

4. UKHSA. Inadvertent vaccination in pregnancy (VIP)

5. Tan MP, Koren G. ‘Chickenpox in pregnancy: revisited’ Reproductive Toxicology: May 2006, volume 21, issue 4, pages 410 to 420

6. Zhang HJ, Patenaude V, Abenhaim HA. ‘Maternal outcomes in pregnancies affected by varicella zoster infections: population-based study on 7.7 million pregnancy admissions’ Journal of Obstetrics and Gynaecology Research: January 2015, volume 41 issue 1, pages 62 to 68