Observational, Prospective Cohort Study of the Immunogenicity and Safety of SARS-CoV-2 Vaccines Administered During Pregnancy or Postpartum and Evaluation of Antibody Transfer and Durability in Infants

SARS-CoV-2, the novel coronavirus that causes Coronavirus Disease 2019 (COVID-19) disease, first emerged in Wuhan, China in December 2019 and has continued to spread globally. SARS-CoV-2 is highly transmissible between humans. A number of public health measures, including social distancing, avoidance of large congregations, particularly indoors, and the wearing of face masks, have been introduced to prevent spread of the virus. However, once these measures are relaxed, unless population immunity exceeds herd immunity thresholds, recrudescence of SARS-CoV-2 is expected. This underscores the urgent need for a safe and effective SARS-CoV-2 vaccine.

While all vaccines in late-stage development are based on the SARS-CoV- 2 S glycoprotein, they differ in other important characteristics, including manufacturing platform, number of doses, and immunogenicity and safety profiles. Two messenger RNA (mRNA)-based vaccines BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (NIAID-Moderna) were granted Emergency Use Authorization (EUA) by the U.S. FDA based on high demonstrated efficacy against symptomatic infection and severe disease in diverse populations. Janssen (Johnson & Johnson) was also granted EUA for their single dose nonreplicating adenovirus vector vaccine. None of these large vaccine trials enrolled pregnant or lactating women (except for a small number of lactating women who were enrolled in the Janssen study).

The mRNA vaccines are being distributed to prioritized population groups, and other vaccines are expected to follow as they receive EUA approval. The Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) gave a permissive recommendation for pregnant individuals who are in a priority group to receive SARS-CoV-2 vaccines based on risk of exposure or comorbidities. In addition, some states have included pregnant individuals in priority groups based on pregnancy itself being considered a high-risk condition by CDC. Thus, pregnant individuals are choosing to receive these vaccines under EUA, without trial data on safety and efficacy. There are neither data on the safety of SARS-CoV-2 vaccines in lactating women nor on the effects of mRNA or other vaccines on the breastfed infant or on milk production/excretion. Current EUA vaccines are not thought to be a risk to the breastfeeding infant.

Currently, additional doses of SARS-CoV-2 vaccines are being considered to enhance durability and breadth of protection, particularly against variant strains. On August 25, 2021, Pfizer submitted a supplement to their Biologics License Application (BLA) for their mRNA vaccine seeking approval for administration of an additional dose, and other manufacturers are expected to follow. In the setting of this rapidly evolving regulatory and policy environment, it is important that data on kinetics and durability of maternal and infant antibodies be generated for all vaccine regimens, including any additional doses beyond the primary series that may be administered to pregnant women.

Vaccines for pregnant individuals, such as influenza, tetanus and pertussis vaccines, are one of the most important public health measures globally to reduce disease in both mothers and infants in the first months of life. Various organizations support the position that pregnant and lactating women are a priority population and must not be excluded from the SARS-CoV-2 vaccine allocation strategy.