Study: Vaccinated Women’s Successful Conception Rate Lower than Unvaccinated Women

Simian Practicalist
May 2
2 min read

A pre-print study by V. Manniche et al titled “Rates of Successful Conceptions According to COVID-19 Vaccination Status: Data from the Czech Republic” posted on 29 April 2025 confirms, at least generally, that the vaccines are harmful to fertility.

The paper is merely 6 pages and it is an easy read. The introduction, under the veneer of reminding the audience, gives the middle finger to Big Pharma:

Unfortunately, the potential influence on reproductive health was not assessed in randomized preauthorization trials of COVID-19 vaccines…

The researchers used data from the Czech Republic since it is “one of the few countries where nationwide birth data are available for women who were vaccinated or unvaccinated for COVID-19”, thus enabling a comparison of the two groups.

The study period was between January 2021 and December 2023 using monthly data for women aged 18–39 years. A “successful conception” (SC) is defined as that which results in a live birth 9 months later. A vaccinated woman is one who has received at least one dose. Most of the vaccines administered were Pfizer.

SC rates for women vaccinated before SC were generally much lower than expected based on their share of the total population of women (Figure 1A and B). For example, at the end of June 2021, where 39% of all women had been vaccinated, those vaccinated before SC contributed only 7% of all SCs. In June 2021, a sharp increase in the rate of SC was observed for women unvaccinated before SC, and this higher rate was maintained over the succeeding 6-month period. During 2022, rates of SCs stabilized in both women that were vaccinated and unvaccinated before SC. However, throughout 2022, SC rates remained about 1.5 times higher for women that were unvaccinated before SC compared with those that were vaccinated before SC (Figure 1B).

One of the obvious weaknesses of the study is that it does not tell us whether these women were trying to become pregnant. It is possible women who wanted children deliberately remained unvaccinated.

However, if unvaccinated women wanted children and vaccinated women didn’t want children anyway, then SC rates should be more-or-less steady throughout the study period. Indeed, the researchers point out that

…the total fertility rate in the Czech Republic decreased from 1.83 births per 1000 women in 2021, to 1.62 in 2022, and 1.45 in 2023, and self-selection bias, therefore, does not seem to fully explain the observed link between vaccination status and SC rates.

Also, in a nationwide study involving approximately 1.3 million women aged 18–39 years, all types, whether it is their intent regarding children or their health conditions, are included anyway.

In other words, the “big picture” is still valid. Even though the specific causal mechanisms are not clear, it is clear that SC rates for vaccinated women are lower than for unvaccinated women.