Guidance

Chickenpox and shingles vaccines: advice for pregnant women

Updated 25 June 2018

1. 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, 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.

Both chickenpox vaccine (Varilrix® and Varivax®) and shingles vaccine (Zostavax®) are live vaccines that contain varicella-zoster virus that has been carefully weakened to safely protect against disease. Shingles vaccine contains a higher dose of the same weakened varicella-zoster virus that is in the chickenpox vaccine.

2. Vaccines given in pregnancy or shortly before conception

No specific risk has been associated with the weakened varicella-zoster virus used in these vaccines when women have been immunised during pregnancy or shortly before becoming 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.

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. Information on the first 10 years of the pregnancy registry, and more recently to March 2012 has been published [1] [2]. No cases of 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.

Between March 1995 and March 2012, there were 928 reports of women who inadvertently received chickenpox vaccine up to 3 months before pregnancy or at any time during pregnancy, and whose pregnancy outcomes were known, available for analysis, and considered complete. Of these reports 860 were received before the outcome of pregnancy was known (prospective reports). No conditions consistent with fetal varicella syndrome were reported. This included 95 babies born to women who were not immune to chickenpox and were exposed during the high-risk period for congenital varicella syndrome (first and second trimester of pregnancy) and who were reported prospectively to the registry. The overall rate for major birth defects in the registry among live-born infants was similar to that in the general population.

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

3. Pregnant women who have received chickenpox vaccine

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

4. Pregnant women who have received shingles (Zostavax) vaccine

Women should be reassured that the weakened varicella-zoster virus in shingles vaccine has not been linked to specific problems in babies born to women who have received vaccines containing this virus whilst pregnant. Any action taken is being done as a matter of precaution because most information on safety has been obtained from women who were immunised with chickenpox vaccine in pregnancy and shingles vaccine contains higher levels of the same weakened virus.

Women immunised with shingles vaccine after week 20 of pregnancy should be further reassured that the timing of vaccination puts them outside the risk period for congenital problems. Most women of child-bearing age in the UK are known to be immune to varicella-zoster virus. If women are immune when they receive shingles vaccine the vaccine will simply boost their existing antibodies against varicella zoster virus, as it would if they came across the natural diseases.

It is important to find out as soon as possible whether the woman who received shingles vaccine was already immune. If a pregnant woman immunised with shingles vaccine is known to have had chickenpox or shingles disease or 2 doses of a chickenpox vaccine and is not immunosuppressed she can be reassured that she is protected from infection. The shingles vaccine will boost her existing antibodies against varicella zoster virus and there is no reason for any further action. This is the same advice you would give a woman with the same history if she was exposed to natural disease (chickenpox or shingles) whilst pregnant.

If a pregnant woman is uncertain as to whether she has had chickenpox or shingles disease, or is not known to be immune, and receives shingles vaccine whilst pregnant, she should be offered testing to establish her immunity as early as possible.

If a woman is found to be immune on testing she can be reassured that the shingles vaccine will boost her existing antibodies against varicella zoster virus and there is no reason for any further action.

If testing shows that a woman is not immune to chickenpox she may be offered treatment but the value of this will be discussed with national experts. Treatment should ideally be given within 7 days, but can be given up to 10 days after vaccination, for it to be of any potential benefit.

5. The UK Vaccine in Pregnancy Surveillance programme

All exposures to 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 Department of UK Health Security Agency. 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. These data will be used to better inform pregnant women who are inadvertently immunised, their families and health professionals who are responsible for their care.

6. 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.

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 [3]; in a more recent study of almost 1000 pregnant patients with chickenpox, the rate of pneumonia was 2.5% with no maternal deaths, reflecting improved medical care and use of aciclovir [4]. 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 has not been found to cause these problems.

7. 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 1400 mothers who had varicella 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 has not been found to cause these problems.

8. Footnotes

1. 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 2008 Mar 1;197 Suppl 2: S178 84.
2. 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.MMWR Morb Mortal Wkly Rep. 2014 Aug 22;63(33):732 to 733.
3. Tan MP, Koren G. ‘Chickenpox in pregnancy: revisited’. Reproductive Toxicology 2006. May 21:410-20.
4. 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 2015 January 41: (1) 62 to 68.