Infants have high COVID-19 antibody levels when mothers are vaccinated during pregnancy

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Experts found that protection from the virus persisted through the first six months of infants’ lives

A new study conducted by researchers from Massachusetts General Hospital explored how getting a COVID-19 vaccine during pregnancy may impact infants’ infection risk.

According to their findings, infants had higher levels of COVID-19 antibody levels at six months old when their mothers were vaccinated during pregnancy. Conversely, infants had lower levels of these antibodies when their mothers were unvaccinated but had been infected with COVID-19.

“While it’s still unclear just how high the [antibody levels] need to be to completely protect an infant from COVID, we know anti-spike IgG levels correlate with protection from serious illness,” said researcher Dr. Andrea Edlow. “The durability of the antibody response here shows vaccination not only provides lasting protection for mothers, but also antibodies that persist in a majority of infants to at least six months of age.”

Protecting infants’ health

The researchers had 77 vaccinated mothers and 12 unvaccinated mothers who had tested positive for COVID-19 during pregnancy participate in the study; the women had either received the vaccine or tested positive for COVID-19 between weeks 20 and 32 of pregnancy. The researchers followed up with the infants after birth to test their antibody levels when they reached two months old and six months old. 

The study showed that antibody levels were the highest for infants born to mothers who were vaccinated as opposed to mothers who had tested positive for COVID-19. By the time the infants were two months old, 98% of those born to vaccinated mothers had high levels of the immunoglobulin G (IgG) antibody associated with COVID-19. 

At the six-month mark, the differences between the two groups became more apparent. Compared to less than 10% of infants born to unvaccinated mothers who had detectable antibody levels at six months, nearly 60% of infants born to vaccinated mothers had detectable antibody levels at six months old. 

The researchers hope these findings shed light on how COVID-19 vaccines can protect both mothers and infants from infection. Moving forward, they hope these results encourage more pregnant women to receive a COVID-19 vaccine. 

“Many interested parties from parents to pediatricians want to know how long maternal antibodies persist in infants after vaccination, and now we can provide some answers,” said Dr. Edlow. “We hope these findings will provide further incentive for pregnant people to get vaccinated, especially with the emergence of new variants of concern like Omicron.” 

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