Rates of Successful Conceptions According to COVID-19 Vaccination Status: Data from the Czech Republic

Background/Objectives: Adverse effects of COVID-19 vaccination on human menstrual cycle characteristics have been observed, but limited data are available on the relationship between COVID-19 vaccination status and birth rates. Therefore, we used nationwide data from the Czech Republic to examine rates of successful conceptions (SCs), i.e., conceptions leading to live births 9 months later, for women who were either vaccinated or unvaccinated against COVID-19 before SC. Methods: Summary monthly COVID-19 vaccination and birth data for women aged 18-39 years in the Czech Republic were retrieved for the period from January 2021 to December 2023. The numbers of SCs per month per 1,000 women were calculated for preconception-vaccinated or unvaccinated women, respectively, as well as the number of SCs per month per 1,000 women for all women aged 18-39 years. Results: During the study period, there were approximately 1,300,000 women aged 18-39 years in the Czech Republic, and the proportion of COVID-19-vaccinated women increased until reaching a steady state of around 70% by the end of 2021. During the entire study period, SCs per 1,000 women were considerably lower for women who were vaccinated, compared to those that were unvaccinated, before SC. Furthermore, SC rates for the vaccinated group were generally much lower than expected based on their proportion of the total population. Conclusions: In the Czech Republic, SC rates were substantially lower for women vaccinated against COVID-19 before SC than for those who were not vaccinated. These hypothesis-generating and preliminary results call for further studies of the potential influence of COVID-19 vaccination on human fecundability and fertility.