COVID-19 vaccination and declining fertility? The trend is unrelated to vaccination.

Vaccinated × Unvaccinated Women: Did Their Fertility Patterns Differ?

The debate over the impact of COVID-19 vaccination on fertility has been highly intense in recent years. However, there has often been a lack of data that would allow researchers to distinguish the actual effect of vaccination from differences between groups that already existed beforehand.

At the Young Demographers 2026 conference, demographer Eva Waldaufová from the Faculty of Science at Charles University presented an analysis of Czech population data that offers an empirical perspective on this debate.

What Was Studied

The research team used linked data from the National Health Information System, combining records on COVID-19 vaccination with women’s birth histories.

The key question was:

Do vaccinated and unvaccinated women differ in their fertility patterns — and if so, did these differences emerge only after vaccination, or were they already present before the pandemic?

Differences Existed Before the Pandemic

The analysis shows that the reproductive behaviour of vaccinated and unvaccinated women differed even before 2020.

Vaccinated women:

• more often postpone their first child (frequently until after age 30),
• show a higher probability of first birth at older ages.

Unvaccinated women:

• have a similar probability of having a second child as vaccinated women,
• but tend to give birth at younger ages,
• and more frequently have third and higher-order births.

These patterns suggest broader social and value-based differences between the groups that predated the pandemic.

Post-Pandemic Fertility Decline

After 2020, a decline in fertility was observed in both groups.

• affects both vaccinated and unvaccinated women,
• follows a similar dynamic,
• and the data do not indicate that it was caused by vaccination itself.

What Does This Mean?

The results show that changes in fertility cannot simply be attributed to vaccination. Reproductive behaviour is long structured by socioeconomic factors, values, and life-course trajectories.

In other words, differences between vaccinated and unvaccinated women are not a new phenomenon of the pandemic — rather, the pandemic made them more visible.