Ingredients Vaccination and pregnancy
Posted: 01/13/2011; Expert Rev Vaccines. 2010;9(12):1411-1422. © 2010 Expert Reviews Ltd.
The recent introduction of oil-in-water emulsions as adjuvants in several pandemic vaccines, such as the H1N1 vaccine, has challenged regulatory authorities to establish their safety in the general population, as well as in specific populations. Pregnant women were advised to be a target group for H1N1 vaccination owing to the risk of this group developing serious complications with this infection. However, the addition of adjuvants to the H1N1 vaccine has initiated a discussion on the safety of adjuvanted vaccines in this special population. Changes in the maternal immune system are essential for acceptance of the fetus and for development of the placenta. The potential effects on pregnancy of interfering with this uniquely adapted immune balance through the induction of proinflammatory reactions such as those induced by adjuvanted vaccines have only been studied rarely. Here, we review the available information and discuss how vaccination may interfere with pregnancy, fetal development and pregnancy outcomes.
Little is known about the safety of adjuvanted vaccines during pregnancy, particularly with regard to the recently introduced adjuvanted vaccines. It is slowly becoming recognized that exclusion of pregnant women from clinical trials withholds them from safe and effective treatment. This is very true for vaccination during pregnancy, especially when using adjuvanted vaccines. The safety of adjuvanted vaccines in pregnant women has not been tested in clinical trials. A simple extrapolation of safety data of vaccines from the nonpregnant populations to the pregnant population is impossible owing to the changes occurring in the immune system during pregnancy. Proinflammatory stimuli that are present in vaccines, in particular in adjuvanted vaccines, may induce a stronger immune response in pregnant individuals, since pregnant individuals have been shown to be more sensitive to proinflammatory stimuli than nonpregnant individuals.[74–78] Moreover, vaccination may negatively affect the immune balance needed for a successful pregnancy in women. Consequently, vaccination may increase the risk of breaking immune tolerance against the fetus. This could theoretically result in pregnancy loss, restricted growth of the fetus and/or the placenta or in the development of preeclampsia.