Vaccine safety in pregnancy and lactation
Significant morbidity due to vaccine-preventable diseases among women and infants could be prevented by immunization of pregnant women. Policy formulation regarding vaccination during pregnancy is challenging because the evidence base to guide decisions is extremely limited. SAGE recently requested GACVS to provide guidance on the safety of vaccines used among pregnant and lactating women.
The concerns include risks to the fetus because there have been a small number of demonstrated instances of live vaccine transmission. For other live vaccines and all inactivated vaccines no evidence of such risk exists. For newer vaccines, several of which are used primarily in low- and middle-income countries, there is no evidence of pregnancy-related harm. Despite of the lack of apparent safety issues for many vaccines, precautions and contraindications are often included in product labelling with respect to immunization during pregnancy and lactation, thereby limiting their benefit to women. In developing countries, pregnancy is one of the few opportunities for women to be in contact with the health care system.
Several important questions need to be addressed. These include the possibility of assessing safety of vaccines in pregnancy and lactation during the vaccine development process and additional opportunities for generating post-licensure data. Adverse events may occur with vaccination only coincidentally, giving rise to a false perception of increased risk from vaccination during pregnancy. Better understanding and analysis of the frequency of occurrence of adverse events that occur during pregnancy in the absence of vaccination («background rates») would be of great benefit. An agenda for continued monitoring, better definitions, availability of background rates, inclusion of pregnant women in cohort studies, and collaboration with regulatory authorities could be developed and proposed. Likewise, since labelling of vaccines package inserts is highly variable around the world, there is a possible role for WHO to help harmonize practices in this area.
Based on the presentation and discussion, GACVS recognizes the need to address safety issues related to the use of vaccines during pregnancy and lactation. GACVS proposes to review the relevant evidence. It will also consider including methodological points for planning and analysis of clinical trials and post-marketing studies.