COVID Vaccine Appears Protective Against Premature Births
When pregnant women express worry that the COVID-19 vaccine might be harmful to them or their unborn child, pharmacists might want to share new data on how much vaccination appears to reduce the risk of premature births. Find out how dramatically the percentage changed from the beginning of the pandemic to the widespread availability of vaccines.
STANFORD, CA – Pharmacists hear a lot of concerns from expectant mothers about the risks and benefits of receiving COVID-19 vaccines.
A new study provides some information that underscores the importance of vaccination in that group. The report in the Proceedings of the National Academies of Sciences advises that COVID-19 caused a shocking surge in premature births.
https://www.pnas.org/doi/10.1073/pnas.2311573120
But, according to the new analysis of California birth records from Stanford University and University of Wisconsin researchers, vaccines played a central role in returning the early birth rate to pre-pandemic levels.
"The effect of maternal COVID infection from the onset of the pandemic into 2023 is large, increasing the risk of preterm births over that time by 1.2 percentage points," said co-author Jenna Nobles, PhD, a University of Wisconsin-Madison sociology professor.
"To move the needle on preterm birth that much is akin to a disastrous environmental exposure, like weeks of breathing intense wildfire smoke."
Nobles and co-author Florencia Torche, PhD, of Stanford point out that the effects of COVID-19 on infant health “may be among the most enduring legacies of the pandemic.”
They used linked population-level data on siblings born between 2014 and 2023 in birthing facilities with confirmed universal testing to establish that “maternal COVID-19 infection during pregnancy causally, and substantially, increased the risk of preterm birth—an infant outcome with lifelong consequences for health and socioeconomic well-being.”
Their study demonstrates that the effect disappeared by 2022 and makes it clear that the disappearance of this effect happened almost a year earlier in places that were early adopters of COVID-19 vaccination. “The availability of vaccines and the decision to use them may have reduced a serious health burden for the next generation of US children,” the authors advise.
The study posits that In-utero exposure to COVID-19 infection can lead to large intergenerational health effects, adding, “The impact of infection exposure has likely evolved since the onset of the pandemic as new variants emerge, immunity from prior infection increases, vaccines become available, and vaccine hesitancy persists, such that when infection is experienced is as important as whether it is experienced.”
The study team analyzed the changing impact of COVID-19 infection on preterm birth and the moderating role of vaccination. “We offer the first plausibly causal estimate of the impact of maternal COVID-19 infection by using population data with no selectivity, universal information on maternal COVID-19 infection, and linked sibling data,” Torche and Nobles write. “We then assess change in this impact from 2020 to 2023 and evaluate the protective role of COVID-19 vaccination on infant health. We find a substantial adverse effect of prenatal COVID-19 infection on the probability of preterm birth.”
The study found that the impact was substantial during the first two years of the pandemic but had been erased by 2022. “The harmful impact of COVID-19 infection disappeared almost a year earlier in zip codes with high vaccination rates, suggesting that vaccines might have prevented thousands of preterm births,” the researchers suggest. “The findings highlight the need to monitor the changing consequences of emerging infectious diseases over time and the importance of mitigation strategies to reduce the burden of infection on vulnerable populations.”
According to the article, as the SARS-C0V-2 virus spread broadened from July to November of 2020 in California, the risk that a pregnant woman with COVID-19 would give birth more than three weeks before the due date was 5.4% higher than anticipated -- 12.3% instead of 6.9%.
Birth records for California's nearly 40 million people were used in the study, providing information on birth timing and the comparison of sibling births to help control for the pandemic's varied effects on different demographic groups.
The study team found the excess risk of preterm birth fell slightly in early 2021 before declining sharply in 2022, at which point maternal COVID-19 infection in pregnancy caused no excess risk of preterm birth for infants.
"In ZIP codes with the highest vaccination rates, the excess risk of preterm birth declines much faster. By the summer of 2021, having COVID-19 in pregnancy had no effect on preterm birth risk in these communities. It takes almost a year longer for that to happen in the ZIP codes with the lowest vaccine uptake," Nobles points out in a University of Wisconsin press release.
"That highlights how protective COVID vaccines have been. By increasing immunity faster, early vaccination uptake likely prevented thousands of preterm births in the U.S."
She urged pregnant women to be vaccinated. "One big contributor to vaccine hesitancy is that people are worried about safety for the fetus and about the ability to get pregnant.
"We already know there is very little evidence of adverse effects of vaccination on fetal development. The results here are compelling evidence that what will actually harm the fetus is not getting vaccinated. That's a message practitioners can share with concerned patients."
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