Can the type of delivery affect a child's risk of getting measles after vaccination? The researchers now say that children born via C-section are at more than double the risk of getting measles after a single dose of vaccine compared to those born naturally.

The research team from the University of Cambridge, UK, and Fudan University, China, who led a recent study found that a single dose of measles vaccine is 2.6 times more likely to be completely ineffective in children born by cesarian. To have robust protection against measles, children born with C-sections should receive two doses of the vaccination, according to the results published 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. 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," said Professor Henrik Salje joint senior author of the report.

The findings were based on data from previous studies that included more than 1500 children in Hunan, China. To understand how measles antibodies in the blood changed during the first few years of a child's life and after the vaccination, blood samples were taken every few weeks from the time of birth to the age of 12.

"They found that 12% of children born via cesarean section had no immune response to their first measles vaccination, as compared to 5% of children born by vaginal delivery. This means that many of the children born by C-section did not 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," the news release stated.

Studies show that vaginal birth transfers a wider variety of microbes from mother to baby, which can strengthen their immune system. The researchers believe that the increased risk of measles among cesarean birth children is also linked to the difference in the development of the infant's gut microbiome.

"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 Professor Salje.