A study released today in the Proceedings of the National Academy of Sciences suggests that immunisation probably saved thousands of premature births that would have otherwise occurred in California due to the considerable increase in risk of preterm birth caused by the COVID-19 epidemic.
However, a year after the introduction of COVID-19 vaccinations, that risk almost vanished in ZIP codes with high vaccination rates, indicating that immunisation was a critical tactic in reducing the risk of premature birth brought on by SARS-CoV-2 infection.
A preterm birth occurs when a baby is born before 37 weeks of pregnancy.
According to a press release from the university, study author Jenna Nobles, PhD, of the University of Wisconsin–Madison, “having COVID-19 in pregnancy had no effect on preterm birth risk in these communities by summer 2021.” “It takes almost a year longer for that to happen in the ZIP codes with the lowest vaccine uptake.”
The study highlights the significance of maternal COVID-19 vaccination and indicates that the US vaccination effort probably spared thousands of premature babies.
Comparing the Birth Timing of Siblings
In order to account for the pandemic’s effects on various demographic groups, Nobles and Florencia Torche, PhD, of Stanford University, examined California birth certificates and compared sibling births. Results were compared to unaffected previous births in cases when women tested positive for COVID-19 during childbirth.
“Matched-sibling data support a fixed-effects approach comparing ‘treated’ infants exposed to COVID-19 infection in utero with their ‘untreated’ siblings,” the researchers said. In the analysis, every birth between 2014 and 2023 was taken into account.
Preterm births are more likely to occur when there is an infection during pregnancy, up 1.3 percentage points from 7.1% to 8.4%, when compared to siblings who are not impacted by COVID-19 infections.
“This effect is roughly equivalent to in utero exposure to a 9 percentage point increase in the area-level unemployment rate or to high-intensity wildfire smoke for 20 [days]—an enormous impact,” the researchers concluded.
Significant Impact in 2020
COVID-19 Up until the end of 2020, 19 infections had the largest effect on preterm birth rates, increasing the chance of preterm delivery by an estimated 5.4 percentage points (from 6.9% to 12.3%, a 78% increase).
However, the impact diminishes through 2021 and becomes nonexistent by 2022, as the authors discovered, even throughout the Omicron outbreak.
COVID-19’s effects on newborn health might be one of the pandemic’s most lasting repercussions.
Despite the lack of vaccination status information in California birth records, the authors were nevertheless able to determine the effect of vaccination on birth outcomes using ZIP code data. In California, vaccination rates rose dramatically in the spring and early autumn of 2021 before levelling off in March 2022 at almost 70% of the population.
“Until May 2021, the effects of COVID-19 are comparable in places with high and low immunisation rates. This result is consistent with the hypothesis that vaccinations reduced the detrimental effect of COVID-19 infection on infant health, given that immunisations were not accessible until the spring of 2021,” the investigators said.
According to Torche, “one of the pandemic’s most lasting effects may be its effects on infant health,” according to a Stanford University news release. “I hope the study provides strong evidence supporting the benefits of vaccination for the health of the next generation.”
She continued, “Unfortunately, even if the adverse impact of COVID-19 infection on preterm birth has plummeted to zero, this adverse impact is likely to emerge again as the virus continues to evolve and mutate, and as vaccine-driven immunity wanes.”