Hungarian study suggests COVID-19 vaccines during pregnancy do not cause lasting neurological changes in offspring

Research from Hungary indicates that COVID-19 and influenza vaccines administered during pregnancy lead to only mild and temporary effects in mouse offspring, contrast­ing with the lasting behavioural changes caused by infection. The findings support vaccination as a safer option for maternal and fetal health, though further human studies are needed.

Researchers in Hungary have reported that COVID-19 and influenza vaccination during pregnancy does not produce the same neurological changes in offspring as infection itself, in a mouse study that adds to the evidence base around maternal immunisation. According to HUN-REN Kísérleti Orvostudományi Kutatóintézet, the work found that infection-mimicking treatment triggered long-lasting behavioural patterns in mouse pups, while vaccination led only to mild, temporary differences.

The study, published in Translational Psychiatry, compared the effects of a virus-like immune challenge with those of an mRNA COVID-19 vaccine and an influenza jab in pregnant mice. The researchers then followed the offspring into both juvenile and adult life, examining social behaviour, movement, learning and repetitive actions, as well as immune responses in the mother and fetus. Their results suggested that the infection-like treatment caused strong inflammation in the mother and developing brain, along with persistent changes in behaviour and lower levels of BDNF, a protein linked to neuron survival and growth, in parts of the adult brain.

By contrast, the vaccine exposures produced a much weaker immune response in the mother and no clear inflammatory effect in the fetal brain. The team reported only small, sex- and age-dependent differences in young animals after vaccination, and said these had disappeared by adulthood. They did not form the kind of consistent pattern associated with autism-like behaviour in the infection model. The findings are in line with earlier research published in Frontiers in Immunology, which also concluded that maternal influenza vaccination does not harm offspring neurodevelopment.

Beáta Sperlágh, who leads the Molecular Pharmacology Research Group at HUN-REN KOKI, said the real choice in pregnancy is not between vaccination and doing nothing, but between vaccination and the risk of infection, which can have more severe and lasting consequences. The researchers stressed, however, that the new findings come from mice, not people, and said further studies in humans are needed to assess the long-term effects of vaccination on neurodevelopment. Even so, they argued that the model supports a simple conclusion: preventing infection matters more than avoiding the comparatively mild immune response caused by vaccination.