A new study of almost 200,000 newborns in Sweden and Norway shows that maternal receipt of the COVID-19 vaccine during pregnancy poses no risk to infants, and instead prevents babies from suffering serious complications.
Moreover, the mortality rate for babies born to mothers who were vaccinated during pregnancy was half the rate of those whose mothers were unvaccinated. The study appeared yesterday in JAMA. The authors caution, however, that they were unable to explain why the mortality risk was so reduced among infants whose mothers were vaccinated.
"A direct vaccine effect is unlikely," said Mikael Norman, PhD, first author of the study in a press release from the Karolinska Institutet in Stockholm, Sweden, where he practices. "Previous studies have shown that the vaccine does not cross the placenta and that it cannot be found in umbilical cord blood…No matter how we look at it, the finding remains and therefore, we cannot say what the lower risk of death among infants of vaccinated women relates to."
The study included national birth registry data from births from gestational week 22 and onwards after COVID-19 vaccines were available in both countries. Babies included in the study were born from June 2021 to January 2023.
Half the risk of infant death
In total, 48% of mothers had been vaccinated with one or more doses of an mRNA vaccine against COVID-19 in pregnancies of 196,470 newborns.
In addition to lower mortality rates by a half, infants born to vaccinated mothers had lower odds for neonatal nontraumatic intracranial hemorrhage (event rate, 1.7 vs 3.2/1,000; adjusted odds ratio [aOR], 0.78; 95% confidence interval [CI], 0.61 to 0.99), and hypoxic-ischemic encephalopathy (1.8 vs 2.7/1000; aOR, 0.73; 95% CI, 0.55 to 0.96).
There were no cases of myocarditis or thrombocytopenia seen in the study, as well as no increased risk for respiratory distress syndrome or necrotizing enterocolitis.
These findings may provide reassurance to public health authorities, clinicians, pregnant individuals, and their families.
"These findings may provide reassurance to public health authorities, clinicians, pregnant individuals, and their families that infants are not at higher risk of adverse events due to COVID-19 vaccination during pregnancy," the authors concluded.