The Costs of Contradictory Messages About Live Vaccines in Pregnancy

The increased risk of harm from COVID-19 infection in pregnancy highlights the importance of including pregnant people in COVID-19 vaccine development and deployment. Promising vaccines being developed include replication-competent platforms, which are typically contraindicated during pregnancy because of theoretical risk. However, replicating vaccines are administered in and around pregnancy, either inadvertently because of unknown pregnancy status or when recommended.The historical cases of Ebola virus, yellow fever, and rubella demonstrate that contradictory messages around the safety of live vaccines in pregnancy have critical public health costs. First, restricting study or use of replicating vaccines in pregnancy may delay or deny access to the only available protection against deadly diseases. Additionally, not vaccinating pregnant people may slow epidemic control. Finally, uncertainty and worry around the safety of live vaccines may lead to terminations of otherwise desired pregnancies after inadvertent vaccination in pregnancy.If one of the vaccines deployed to combat the current global COVID-19 pandemic is replication competent, historical cases offer important lessons for ethical and effective protection for pregnant populations.