C-section birth significantly reduces measles vaccine efficacy in infants

A joint study by researchers from the University of Cambridge and Fudan University has uncovered a significant association between caesarean section (C-section) births and impaired immune response to the first dose of the measles vaccine in infants.

The findings, published in the prestigious journal Nature Microbiology [1], highlight the potential long-term impacts of birth mode on vaccine-induced immunity.

C-section birth significantly reduces measles vaccine efficacy in infants

The study analyzed data from over 1,500 children in Hunan, China, including serial blood samples collected from birth to age 12. By tracking measles antibody levels, the researchers found a striking disparity in vaccine efficacy based on delivery mode. Approximately 12% of infants born via C-section exhibited no detectable immune response following their first measles vaccination, compared to only 5% of those born vaginally.

C-section’s long-term consequences on immunity

“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,” explained Professor Henrik Salje, joint senior author from the University of Cambridge’s Department of Genetics.

The proposed mechanism behind this phenomenon is linked to the development of the infant’s gut microbiome – the vast community of microorganisms residing in the gastrointestinal tract. Previous studies have demonstrated that vaginal delivery facilitates the transfer of a more diverse array of maternal microbes to the newborn, potentially priming the immune system more effectively.

“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,” Salje elaborated.

Second vaccine dose induces robust immune response

While the first measles vaccine dose was less effective in C-section infants, the researchers found that the second dose successfully induced a robust immune response, underscoring the importance of completing the full vaccination schedule.

Measles, a highly contagious viral disease, poses a significant public health threat, with outbreaks occurring when vaccination rates dip below the critical 95% threshold required for herd immunity. The World Health Organization reported that in 2022, only 83% of children worldwide received their first measles vaccine dose by their first birthday – the lowest coverage since 2008.

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

With an increasing global trend towards C-section deliveries, accounting for a third of births in the UK and over half in countries like Brazil and Turkey, the study’s findings have profound implications for vaccination strategies and public health policies.

“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,” Salje emphasized.

The research underscores the intricate interplay between birth mode, microbiome development, and vaccine-induced immunity, highlighting the need for targeted interventions and education to ensure optimal protection against preventable diseases like measles.


  1. Wang, W. et al: ‘Dynamics of measles immunity from birth and following vaccination.’ Nature Microbiology, 13 May 2024.
    doi: https://doi.org/1038/s41564-024-01694-x