Manniche, V., Fürst, T., Schmeling, M., Gilthorpe, J. D., & Hansen, P. R. (2025). Rates of successful conceptions according to COVID-19 vaccination status: Data from the Czech Republic. The International Journal of Risk & Safety in Medicine, 36(4), 302-306. https://doi.org/10.1177/09246479251353384
Manniche V, Fürst T, Schmeling M, Gilthorpe JD, Hansen PR. Rates of successful conceptions according to COVID-19 vaccination status: Data from the Czech Republic. Int J Risk Saf Med. 2025;36(4):302-306. doi:10.1177/09246479251353384
Manniche, Vibeke, et al. "Rates of successful conceptions according to COVID-19 vaccination status: Data from the Czech Republic." The International Journal of Risk & Safety in Medicine, vol. 36, no. 4, 2025, pp. 302-306.
For EndNote, Zotero or Mendeley:
Open access
No open license is recorded for this paper. Reuse terms are set by the publisher.
COVID-19-vaccinated Czech women had lower successful conception rates
In a national Czech study, researchers tracked monthly conception counts among about 1,300,000 women aged 18-39. Women vaccinated for COVID-19 before conception had much lower rates of successful conception than women who were not vaccinated. A successful conception was a pregnancy that led to a live birth about nine months later.
Key Findings
Across about 1,300,000 women aged 18-39 in the Czech Republic, vaccination coverage climbed through 2021 and settled at around 70% by the end of 2021.
At least from June 2021, monthly successful conceptions per 1000 women were considerably lower for women vaccinated before conception than for women unvaccinated before conception.
Throughout 2022, rates of successful conception stayed about 1.5 times higher for women unvaccinated before conception than for women vaccinated before conception.
Rates for women vaccinated before conception were generally lower than expected from their proportion of the total population of women.
The mRNA vaccines Comirnaty (Pfizer-BioNTech) and Spikevax (Moderna) made up 96% of all administered doses, used in an 11:1 ratio.
Interpretation
This is a national look at COVID-19 vaccination and birth counts for women aged 18 to 39, drawn from many cities, towns, and smaller clinics spread across the whole Czech Republic over several years. The authors note that women who wanted a pregnancy may have put off the vaccine before trying, which could play a role in the pattern seen. The findings support larger studies of how COVID-19 vaccination affects fertility and the chance of conceiving.
RRM Context
The authors tie their question to known changes in menstrual pain, flow, and cycle length after vaccination. They say these changes could affect the chance of conceiving in a given cycle. Cycle charting tracks these same details, including the day of ovulation, for each woman or couple, cycle by cycle, month after month. National birth counts hold no such cycle-level detail. Restorative reproductive medicine treats the menstrual cycle as a vital sign, worth tracking just like blood pressure or heart rate.
Our editorial summary of this paper, not the article's abstract.
Abstract
Background
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.
Objectives
Therefore, 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.
Methods
Summary 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.
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 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.
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.
