On Nov. 27, 2023, University of Wisconsin-Madison researchers released a study that showed COVID-19 caused an alarming surge in premature births, but vaccines were key to returning the early birth rate to pre-pandemic levels, according to a new analysis of California birth records.

The researchers They found the excess risk of preterm birth fell slightly in early 2021 before dropping steeply in 2022, at which point maternal COVID-19 infection in pregnancy caused no excess risk of preterm birth for infants, and vaccines contributed to that decrease.