Cervarix does not increase miscarriage risk

The bivalent human papillomavirus vaccine Cervarix is not associated with an increased risk of miscarriage, say investigators in North America (Br Med J 2010;340:c712).

Their analysis was prompted by a difference in miscarriage rates between vaccinated and non-vaccinated women identified by an interim analysis of the PApilloma TRIal against Cancer In young Adults (PATRICIA) trial (Lancet 2007;369:2161–70). Their pooled analysis also included the Costa Rica Vaccine trial and involved a total of 26 130 women, 3599 pregnancies and 373 miscarriages.

There was no overall difference in the incidence of miscarriage in vaccinated women and controls who received the hepatitis A vaccine (11.5 versus 10.2 per cent, p=0.16). The difference was greater when the analysis was confined to pregnancies beginning within three months of the nearest vaccination (13.7 versus 9.2 per cent).

The investigators say ‘the small increase seen in risk of miscarriage in the subgroup of pregnancies conceived within three months of vaccination is compatible with chance, but does raise concern for a vaccine that is likely to be administered to millions of women of reproductive age’. They recommend further research to clarify the possible risk if pregnancy occurs soon after vaccination.