Vaccinated vs. Unvaccinated: Women with Diverging Fertility Patterns

Jitka Slabá, Charles University - Faculty of Science
Eva Waldaufová , Charles University, Faculty of Science
Anna Štastná, Charles University
Krystof Zeman, Vienna Institute of Demography
Jitka Jírová, Institute of Health Information and Statistics of the Czech Republic

The COVID-19 vaccination prompted widespread speculation about its effects on fertility. This study explores fertility patterns among vaccinated and unvaccinated women in Czechia, using individual-level data from the National Health Information System. By linking the Registry of COVID-19 vaccination with the Maternity registry, we analyze fertility behavior within selected female birth cohorts (1976–1991) with childbirth records from 1994 to 2024. Vaccination status is defined as receiving at least one dose of a COVID-19 vaccine. Fertility is observed both before and after vaccination, including the pre-pandemic period, allowing us to assess whether differences between vaccinated and unvaccinated women existed independently of the pandemic or vaccination itself. Our analysis employs the Parity-and-Vaccination Conditional Age-Specific Fertility Rate. This measure effectively controls for demographic differences by restricting exposure only to women at risk of a specific birth order. Results confirm significant, behavioral heterogeneity even before the COVID-19 pandemic: the probability of a first birth is consistently higher among vaccinated women. Conversely, unvaccinated women show higher probabilities of progressing to second and higher-order births, often at younger ages, indicating potential socioeconomic disparities. The observed differences in fertility are driven by structural factors unrelated to COVID-19 vaccination status, since pronounced differences in reproductive patterns between the two groups of women were apparent well before the COVID-19 vaccination campaign began. Furthermore, the overall post-pandemic fertility decline is evident in both groups. Our findings underscore the critical need for robust methodological control, concluding that without it, any direct association between COVID-19 vaccination and fertility remains inconclusive.

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 Presented in Session P3. Families, Fertility, and the Life Course 3