• Posted May 14, 2024

Why C-Section Babies Need 2 Doses of Measles Vaccine

Babies born by C-section are unlikely to receive protection from a single dose of measles vaccine, a new study finds.

A single measles jab is up to 2.6 times more likely to be completely ineffective in C-section babies, compared to those born vaginally. Their immune systems fail to produce antibodies to fight against measles infection.

However, a second follow-up jab does induce robust immunity against measles, researchers report May 13 in the journal Nature Microbiology.

“We’ve discovered that the way we’re born -- either by C-section or natural birth -- has long-term consequences on our immunity to diseases as we grow up,” said co-senior study author Henrik Salje, a lecturer in genetics with the University of Cambridge​ in the U.K..

Measles is highly infectious, and even low vaccine failure rates can significantly increase the risk of an outbreak, researchers said in background notes.

Before the introduction of the measles vaccine in 1963, measles caused an estimated 2.6 million deaths each year, researchers said. The disease starts out like a cold accompanied by a distinctive rash, and can lead to serious complications like blindness, seizures and death.

“We know that a lot of children don't end up having their second measles jab, which is dangerous for them as individuals and for the wider population,” Salje said. “Infants born by C-section are the ones we really want to be following up to make sure they get their second measles jab, because their first jab is much more likely to fail.”

Researchers suspect the failure rate among C-section babies are due to differences in their gut microbes. Vaginal delivery tends to transfer a greater variety of microbes from mother to baby, which can protect the immune system.

“With a C-section birth, children aren’t exposed to the mother’s microbiome in the same way as with a vaginal birth,” Salje said. “We think this means they take longer to catch up in developing their gut microbiome, and with it, the ability of the immune system to be primed by vaccines against diseases including measles.”

About one in three babies (32%) born in the United States are delivered through C-section, according to the March of Dimes.

For the study, researchers used data from a study of more than 1,500 children in Hunan, China, that took blood samples from them every few weeks from birth to age 12.

About 12% of children born through C-section had no immune response to their first measles jab, compared to 5% of children born vaginally, results showed.

As a result, many C-section kids had no measles protection following their first vaccination.

Two doses of the measles jab are needed for the body to mount a long-lasting immune response, but only 83% of kids around the world received one dose by their first birthday in 2022 -- the lowest rate since 2008, researchers said.

“Vaccine hesitancy is really problematic, and measles is top of the list of diseases we’re worried about because it’s so infectious,” Salje said.

More information

The March of Dimes has more about C-section rates.

SOURCE: University of Cambridge, news release, May 13, 2024