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Covid-19 And Pregnancy: Can Vaccine Antibodies Pass On From Mother To Baby?

A study found an effectiveness of 61 per cent in preventing hospitalisation among infants aged up to six months whose mothers got two doses of an mRNA vaccine during pregnancy.

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Women who get vaccinated against coronavirus during their pregnancy can pass on their antibodies to their babies, resulting in better protection against COVID-19 in early infancy, according to a new study from US Centers for Disease Control and Prevention.

The study found an effectiveness of 61 per cent in preventing hospitalisation among infants aged up to six months whose mothers got two doses of an mRNA vaccine during pregnancy.

How antibodies pass from mother to baby?

When a person receives antibodies – rather than producing antibodies themselves, it’s a case of what’s called ‘passive immunity’.

Pregnant women pass on antibodies to babies in the last three months of their pregnancy through placenta. Antibodies are also passed through breastmilk, which means that children who are breastfed have passive immunity for a longer period.

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Passive immunity from a pregnant woman to a child is a common occurrence and has been observed for diseases other than COVID-19 as well. A study published in the New England Journal of Medicine in 2008 found that maternal immunisation with influenza vaccine had a reduction of 63 per cent in laboratory-proven influenza illness in infants up to six months of age and reductions of 29 per cent and 36 per cent in rates of respiratory illness with fever in infants and mothers.

Similar passive immunity is seen in case of chicken pox. The UK National Health Service notes, "If you have had chickenpox, you should have developed immunity against the condition and some of the chickenpox antibodies will be passed to your baby."

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What did the study find?

The study was conducted with 379 children with an average age of two months during July 2021 and January 2022.

Of the children who contracted COVID-19, only 16 per cent had mothers who were vaccinated. Of the children who were COVID-free in the period, the number of vaccinated mothers was double – 32 per cent.

Of the babies admitted to intensive care, mothers of 88 per cent were unvaccinated.

The only child in the study who died of COVID-19 had an unvaccinated mother.

Limitations of the study

The study can show whether there is an association between mothers’ vaccination and lower rates of COVID-19 in their children, but it cannot be used to show that maternal vaccination definitively reduces chances of COVID-19 in children, according to April Rees and Catherine Thornton of Swansea University. 

A ‘randomised controlled trial’-based study would be required to prove such a definitive link.

Official vaccination advice for pregnant women

Finding that the benefits of vaccination against COVID-19 to pregnant women outweigh any potential risks, the Union government has approved the vaccination of pregnant women.

However, pregnant women must make an informed decision to get vaccinated where they understand the risk of COVID-19 along with benefits and potential adverse effects of a vaccine, according to the Union health ministry.

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