Early exploration of COVID-19 vaccination safety and effectiveness during pregnancy: interim descriptive data from a prospective observational study

Objective During December 2020, a massive vaccination program was introduced in our country. The Pfizer-BioNTech, BNT162b2 vaccine was first offered exclusively to high-risk population, such as medical personnel (including pregnant women). In this study we compare short term outcomes in vaccinated vs. non-vaccinated pregnant women. Methods In this prospective observational cohort study, vaccinated and non-vaccinated pregnant women were recruited using an online Google forms questionnaire targeting medical groups on Facebook and WhatsApp. A second questionnaire was sent one month after the first one for interim analysis. Our primary outcome was composite complications in vaccinated and non-vaccinated groups, considered any of the following: vaginal bleeding, pregnancy loss, hypertension, gestational diabetes, and preterm birth. Secondary outcomes included: vaccine side effects, diagnosis of COVID-19 since the last questionnaire, prevalence of vaccinated participants, and reasons for refusal to be vaccinated. Results Overall, 432 women answered the first questionnaire, of which 326 responses were received to the second questionnaire. Vaccination rate increased from 25.5% to 62% within a month. Maternal age, gestational age at enrollment, nulliparity and number of children were similar in both groups. The rate of composite pregnancy complications was similar between vaccinated and non-vaccinated group (15.8% vs 20.1%, p = 0.37), respectively. The risk for COVID-19 infection was significantly lower in the vaccinated group (1.5% vs 6.5%, p = 0.024, Odds Ratio: 4.5, 95% confidence interval 1.19-17.6). Conclusions mRNA vaccine during pregnancy does not seem to increase the rate of pregnancy complications and is effective in prevention of COVID-19 infection.