In the early part of the pandemic, two sociologists found that mothers in California with COVID-19 had a greater risk of preterm delivery, as per a study published in the Proceedings of the National Academy of Sciences. The risk increased from 7.1% among non-infected mothers to 8.3% in those with COVID-19, a relatively small difference of 1.2% that the authors dramatically describe as “roughly equivalent to in utero exposure to high-intensity wildfire smoke for 20 days”.
The study took an interesting twist as they tracked vaccine rollout in California, and divided the State into five zones based on vaccination coverage. The apparent adverse impact of COVID on preterm births diminished quickly in places where vaccines were widely accepted. The difference persisted for almost another year in areas that had low vaccine acceptance.
The impact eventually vanished in January 2022, which coincided with the arrival of Omicron and widespread population immunity. Based on these observations, the authors state that vaccination prevented a large number of preterm births during the pandemic.
