COVID vaccinations did not affect fertility

Childbirth and miscarriage rates were comparable in vaccinated and unvaccinated women, according to a large study in Sweden.

The retrospective study analysed health registry data from approximately 60,000 women aged 18-45 in Jönköping County, Sweden, to examine whether COVID vaccination affected birth rates or pregnancy outcomes. Although birth rates declined during the pandemic, the researchers found no association between vaccination status and childbirth or miscarriage.

'Unsubstantiated rumours about side effects of COVID vaccines still are circulating on social media,' Toomas Timpka, professor of social medicine and public health at Linköping University, told CIDRAP News. As lead author of the study published in Communications Medicine, he said the research 'shows it is very highly unlikely that COVID vaccines have any meaningful negative effect on fertility or childbirth rates'.

Of the women whose records were analysed, around three-quarters had been vaccinated against SARS-CoV-2, the virus that causes COVID-19, between 2021 and 2024, mostly with mRNA-based vaccines. Because the study was retrospective, it was not randomised, but the researchers took age-related variation in childbirth and other relevant factors into account.

The results showed that vaccinated women were three to four percent more likely to give birth than unvaccinated women, and were 14 percent less likely to have a recorded miscarriage. The authors calculated that neither difference between the two groups was statistically significant.

The authors noted that Sweden experienced a decline in births between 1992 and 1998 due to strained public finances and reduced family support. They suggest that the recent drop in childbirths during the pandemic aligns with these longer-term demographic patterns rather than any effect of vaccination.

Previous research has also examined potential links between COVID vaccines and fertility in both men and women (see BioNews 1095, 1100, 1101 and 1146).

'[There have already been] more than a dozen studies showing that COVID vaccination does not reduce the chance of conception,' said Dr Victoria Male, who specialises in reproductive immunology at Imperial College London, and was not involved in the study. 'This should further reassure women that COVID vaccination will not prevent them from getting pregnant or having a baby'.

As some countries have recently revised or narrowed pregnancy-related COVID vaccine guidance (see BioNews 1301), the authors said that their results 'provide evidence to support vaccination policies for women of childbearing age'.