More evidence that pregnant women who receive Covid vaccine pass on protection to their newborns

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  • Pregnant women who are vaccinated with the mRNA vaccines pass on protection to their newborns, a new study shows.
  • The women in the study received either the Moderna or Pfizer-BioNTech vaccines in the US.
  • Further research is needed to determine how long this 'passive immunity' lasts.

Pregnant women who get the mRNA Covid vaccines by Pfizer-BioNTech or Moderna pass high levels of antibodies to their babies, according to a study published in the American Journal of Obstetrics & Gynecology: Maternal Fetal Medicine this month.

The study is one of the first to measure antibody levels in umbilical cord blood to determine whether immunity was provided by coronavirus infection or the vaccines. 

According to the findings, the 36 newborns tested at birth all had antibodies that protect against Covid-19 after their mothers were vaccinated with one of the two vaccines. 

The findings are supported by an earlier study, published in March 2021 in the same journal, which found that not only did all the women – both pregnant and breastfeeding – have robust immunity after vaccination, but that they had passed antibodies to their babies through the placenta. 

Transferred immunity

In the new study, the researchers who are from the NYU Grossman School of Medicine aimed to tell apart whether the antibodies were produced after natural infection or vaccination. To do this, they compared the neonatal (newborn) blood that was created in response to natural infection to those triggered by the vaccines. 

The researchers stressed the difference because antibody responses through natural infection were found not to be sufficiently protective in many people. 

The highest levels of antibodies were found in the cord blood of mothers who were fully vaccinated during the second half of their pregnancies, according to the paper. This observation, the authors said, provides evidence of transferred immunity to infants, known as ‘passive immunity’. The results mean that these infants would have protection against the virus during their first months of life.

Encouraging findings

“Studies continue to reinforce the importance of vaccines during pregnancy and their power to protect two lives at once by preventing severe illness in both mothers and babies,” study co-author Dr Ashley S. Roman, Professor of Obstetrics and Gynecology in the Department of Obstetrics and Gynecology at NYU Langone Health, said in a news release by the university.

She added: “If babies could be born with antibodies, it could protect them in the first several months of their lives, when they are most vulnerable.”

While the study sample size was small, “it is encouraging that neonatal antibody levels are high if women are vaccinated”, said co-author, Dr Jennifer Lighter, associate professor in the Department of Pediatrics, hospital epidemiologist at Hassenfeld Children’s Hospital at NYU Langone.

High levels of antibody transfer via the placenta are not surprising, said Lighter, and is consistent with what is seen with other vaccinations. 

“Our findings add to a growing list of important reasons why women should be advised to receive the Covid-19 vaccine during pregnancy for the added benefit of their newborn receiving crucial protection,” she added.

Additional research

While the findings are certainly promising, the researchers mentioned that additional studies are needed to determine how effective the infant antibodies are, as well as how long protection will last, among other factors.

*For more Covid-19 research, science and news, click here. You can also sign up for our Daily Dose newsletter here.

READ | Pregnant women in SA hospitalised with Covid-19 at high risk of severe illness, death - new study

READ | Covid-19: Three SA experts weigh in on breakthrough infections, immunity, and vaccine hesitancy

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