Measles vaccine less effective in children born by C-section

The measles vaccine does not work well in children delivered by caesarean-section, a new study has revealed. The study conducted by scientists from the University of Cambridge, UK, and Fudan University in China notes that C-section more than doubles the odds of measles vaccine failure.

According to the research published in the journal Nature Microbiology, a single dose of the measles jab is up to 2.6 times more likely to be completely ineffective in children born by C-section, compared to those born naturally.

Failure of the vaccine means that the child’s immune system does not produce antibodies to fight against measles infection, so they remain susceptible to the disease. A second measles jab was found to induce a robust immunity against measles in C-section children.

Measles is a highly contagious viral disease that spreads through respiratory droplets created when an infected individual coughs, sneezes or speaks. According to health experts, even low vaccine failure rates can significantly increase the risk of an outbreak. In Kenya, health authorities reported 392 cases nationwide in 2022. 

According to the researchers, a potential reason for this effect is linked to the development of the infant’s gut microbiome — the vast collection of microbes that naturally live inside the gut. Other studies have shown that vaginal birth transfers a greater variety of microbes from mother to baby, which can boost the immune system.“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 Prof Henrik Salje, senior author of the report.

He added: “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. 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.”

The researchers used data from previous studies of over 1,500 children in Hunan, China, which included blood samples taken every few weeks from birth to the age of 12. This allowed them to see how levels of measles antibodies in the blood change over the first few years of life, including following vaccination.

They found that 12 per cent of children born via caesarean section had no immune response to their first measles vaccination as compared to five per cent of children born by vaginal delivery. This means that many of the children born by C-section did still mount an immune response following their first vaccination.

Two doses of the measles jab are needed for the body to mount a long-lasting immune response and protect against measles. According to the World Health Organization,in 2022 only 83 per cent of the world’s children had received one dose of measles vaccine by their first birthday -- the lowest since 2008.

An increasing number of women around the world are choosing to give birth by caesarean section. The latest data from the National Bureau of Statistics show that births through C-section have almost doubled in the past eight years, from nine per cent in 2014, to 17 per cent in 2022.  

“With a C-section birth, children aren’t exposed to the mother’s microbiome in the same way as with a vaginal birth. 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,” said Salje.

The research was funded by the National Natural Science Foundation of China.