Letters

Varicella vaccine in pregnancy

BMJ 1997; 314 doi: https://doi.org/10.1136/bmj.314.7075.226 (Published 18 January 1997) Cite this as: BMJ 1997;314:226

Testing should be offered to women without a history of chickenpox

  1. Peter V Coyle, Consultant virologista,
  2. Conall McCaughey, Senior registrara,
  3. Dorothy E Wyatt, Principal virologista,
  4. Hugh J O'Neill, Consultant clinical scientista
  1. a Regional Virus Laboratory, Royal Hospitals Trust, Belfast BT12 6BN
  2. b University of Nottingham, Department of Microbiology, University Hospital, Queen's Medical Centre, Nottingham NG7 2UH

    Editor-Daniel S Seidman and colleagues' editorial on giving varicella vaccine to non-immune women to prevent infection during pregnancy addresses an area of growing clinical concern.1 The potential consequences to the fetus resulting from chickenpox in pregnancy are serious.2 The problem stems from a rise in the incidence of primary chickenpox in adults, probably as a result of increased personal living standards delaying exposure to the virus.3 In Northern Ireland over the period 1 January 1995 to 31 August 1996 we established the laboratory diagnosis of acute chickenpox in 28 patients (average age 23 years). The clinical presentation was atypical in several patients, including a 35 year old woman with secondary chickenpox, in whom varicella zoster virus was recovered from an isolated abdominal maculopapule. Eight of the patients (average age 25) were women in the first 20 weeks of pregnancy.

    The results of a cost-benefit analysis of screening for varicella zoster virus IgG versus blanket vaccination of women wishing to become pregnant will depend on the local seroprevalence of the virus. We undertake pre-employment screening of healthcare workers in Northern Ireland, which has a population of roughly 1.5 million and 24 000 births a year; we screen those without a history of chickenpox (currently 30%) for immunity to varicella zoster virus. Extrapolation from this group has allowed us to estimate the seroprevalence of varicella zoster virus among antenatal patients. Table 1 shows our results for female healthcare workers over 20 months. The proportion of male healthcare workers lacking evidence of immunity to varicella zoster virus is similar, and for both sexes the proportion lacking evidence of immunity would be expected to be less than 5% among those with a history of chickenpox.

    Table 1

    Sero prevalence of varicella zoster virus among female health care workers aged 16-45 without a history of chickenpox, Northern Ireland, 1 January 1995 to 31 August 1996

    View this table:

    We have taken the cost of varicella zoster virus IgG assay during the period to be £6 and have assumed that the cost of the vaccine when licensed would be £24. On the basis of these figures, if a policy of testing women without a history of chickenpox was introduced it would cost about £43 200 to screen 24 000 pregnancies a year. For now it seems reasonable to ask women at their first antenatal visit whether they have a history of chickenpox and to offer a varicella zoster virus IgG test to those without such a history. This would allow those found not to be immune to be counselled on the risks of exposure to patients with active chickenpox and would avoid the difficulties of managing contacts after the event.

    References

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    Varicella zoster immunoglobulin should be given after exposure to the virus

    1. William L Irving, Reader in clinical virologyb
    1. a Regional Virus Laboratory, Royal Hospitals Trust, Belfast BT12 6BN
    2. b University of Nottingham, Department of Microbiology, University Hospital, Queen's Medical Centre, Nottingham NG7 2UH

      Editor-Daniel S Seidman and colleagues' editorial on varicella vaccine in pregnancy contains an important inaccuracy: it states that passive immunisation within 96 hours of exposure has not been shown to prevent intrauterine transmission or to alleviate fetal infection.1 In a large prospective study of chickenpox in pregnancy, however, no cases of congenital varicella syndrome or chickenpox in infancy occurred among the 97 pregnancies in which maternal chickenpox occurred after post-exposure prophylaxis with varicella zoster immunoglobulin.2 Specific IgM antibody was found in one (1%) of 89 samples of cord blood tested, compared with 76 (12%) of 615 samples from asymptomatic infants whose mothers did not receive prophylaxis (P=0.003, χ2 test with Yates's correction).

      On the basis of this evidence, pregnant women who are exposed to varicella zoster virus should be encouraged to seek medical advice. Their immune status should then be ascertained and varicella zoster immunoglobulin given to those found not to be immune to the virus; this will attenuate the attack of maternal chickenpox and, for women in the first 20 weeks of pregnancy, decrease the risk of fetal infection.

      References

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