European countries rapidly advised coronavirus disease 2019 (COVID-19) vaccination during pregnancy based on the evidence of first and reassuring data, especially with mRNA vaccines. Besides the close European pharmacovigilance monitoring, Luxembourg set up a prospective study cohort of women vaccinated during pregnancy to collect maternal and embryofetal outcomes.

The study was conducted between June 2021 and October 2023, based on the national vaccination registry. Women were contacted by email and all reported events were retrospectively reviewed by an expert group.

The cohort involved 2335 vaccinated pregnant women of which 476 (20.4%) provided an answer, with 383 (80.5%) reporting no adverse events, 88 (18.5%) reporting a total of 90 adverse events (five reports not assessable). Vaccines were almost exclusively messenger RNA (mRNA) vaccines. Between the women who reported an adverse event and those who did not, no significant difference was identified for vaccine rank and pregnancy trimester. Among the 90 reported events, 73 (81,9%) were considered as without link with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccination. Among the 17 adverse events having a non-excluded link with the vaccine, 16 (94%) had a favorable outcome and/or no pathophysiological explanation in regard to the vaccine. Rates of congenital anomalies and miscarriages were reassuringly lower than in the general population.

Our Luxembourgish cohort study provided results consistent with other European pharmacovigilance surveys and literature data, in agreement with the overall safety of the vaccination against SARS-Cov-2 with mRNA vaccine during pregnancy.