Rates of successful conceptions according to COVID-19 vaccination status: Data from the Czech Republic

Abstract

BackgroundAdverse 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.ObjectivesTherefore, we used nationwide data from the Czech Republic to examine rates of successful conceptions (SCs), that is, conceptions leading to live births 9 months later, for women who were either vaccinated or unvaccinated against COVID-19 before SC.MethodsSummary monthly COVID-19 vaccination and birth data for women in the Czech Republic aged 18-39 years were retrieved for the period from January 2021 to December 2023. The numbers of SCs per month per 1000 women were calculated for preconception-vaccinated or unvaccinated women, respectively, as well as the number of SCs per month per 1000 women for all women aged 18-39 years.ResultsDuring 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 from January 2021 until reaching a steady state of around 70% by the end of 2021. At least from June 2021, SCs per 1000 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 much lower than expected based on their proportion of the total population.ConclusionsIn 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.

Keywords: COVID-19; fecundability; fertility; vaccine.

Figure 1.

(a) Histogram showing the percentage of women in the Czech Republic aged 18–39 years who were vaccinated with at least one dose of a COVID-19 vaccine by the end of the respective month (January-December = 1–12 on the abscissa). (b) Estimates of the number of successful conceptions (SCs) per 1000 women aged 18–39 years according to preconception COVID-19 vaccination status, and SC rates for all these women, respectively. The blue-shaded areas in Figure 1(b) show the intervals between the lower and upper bounds for estimates of actual SC rates for women vaccinated (dark blue) and unvaccinated (light blue) before SC. The large initial divergence between the lower and upper bounds for estimated SC rates for vaccinated women was due to the small sample size, as indicated in Figure 1(a).