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Premature births linked to COVID-19 were halted by vaccines

Researchers have identified a significant increase in premature births linked to COVID-19, which was effectively mitigated by the introduction of vaccines. 

The study highlights the crucial role that vaccines have played in reversing this alarming trend.

Spike in premature births 

Based on the analysis of California birth records, the experts determined that the onset of the COVID-19 pandemic led to a notable rise in premature births. 

Jenna Nobles, a professor of Sociology at the University of Wisconsin–Madison, describes the increase in preterm births as substantial, comparing it to the effects of a major environmental disaster. 

“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 Professor Nobles. “To move the needle on preterm birth that much is akin to a disastrous environmental exposure, like weeks of breathing intense wildfire smoke.”

Key insights

The surge was primarily due to the virus triggering immune and inflammatory responses, as well as deteriorating the placenta, leading to early termination of pregnancies.

During the peak months of July to November 2020, the likelihood of preterm births for mothers with COVID-19 was significantly higher than expected in California. The number of premature births jumped from an anticipated 6.9 percent to 12.3 percent.

COVID-19 vaccines

The researchers found that there was a steep decline in premature births with the advent of COVID-19 vaccines. The team analyzed extensive birth records, covering nearly 40 million people in California, to assess the pandemic’s impact across various demographics.

Notably, areas with higher vaccination rates saw a more rapid decrease in preterm birth risks. 

“In ZIP codes with the highest vaccination rates, the excess risk of preterm birth declines much faster. By summer 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,” said Professor Nobles. 

“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.”

Health implications 

Premature births are the leading cause of infant mortality. Even slight reductions in gestation can lead to significant health and developmental challenges for children, often requiring costly medical interventions.

“And we found similar increases, of about 38%, in the risk of very preterm birth — that is pre-32 weeks — when a child is likely to need neonatal intensive care, with the possibility of developmental delays and serious implications for their families as well,” said Professor Nobles.

This evidence is crucial in addressing vaccine hesitancy among pregnant individuals, alleviating concerns about vaccine safety and emphasizing the greater risk of harm from not being vaccinated.

Ongoing vigilance 

Despite the significant progress made in reducing COVID-related premature birth risks in California, the researchers stress the importance of ongoing vigilance. 

“One big contributor to vaccine hesitancy is that people are worried about safety for the fetus and about the ability to get pregnant,” noted Professor Nobles. 

“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.”

Study implications 

According to the researchers, the results should be a compelling argument in favor of getting vaccinations and boosters, even after COVID-related premature birth risk ebbed in California.

“This is still an evolving epidemic, and the rate of vaccine boosters among pregnant people right now is very low,” said Professor Nobles. 

“The question is, how many more iterations of viral evolution does this need to escape the immunity that we have? It’s miraculous and incredible that we’re now down to essentially zero additional preterm births, but it does not indicate that it’s going to be that way in perpetuity.”

The study is published in the journal Proceedings of the National Academy of Sciences.

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