May 13, 2024

expert reaction to study suggesting birth by C-section is associated with increased odds of measles vaccine failure with a single dose

A study published in Nature Microbiology looks at birth by C-section and measles vaccine failure. 

Prof Alastair Sutcliffe, Professor of General Paediatrics, University College London (UCL), said:

“This interesting study whose primary purpose was to study an unrelated condition and thus less likely to be biased, suggested that children born by caesarian section have a reduced chance of developing antibodies to measles via vaccination than those born by normal vaginal delivery.

“It has been known for some time that there is a poor responder issue with the measles vaccine. The original measles vaccine was poor and didn’t give anywhere near adequate protection, thus MMR was brought in to increase the antigenic load. Measles is a perfidious killer and even now with the live attenuated MMR combination vaccine uptake rates are still needed to get rid of these plagues on humanity (measles, mumps and rubella). This was one of the reasons for the game-changing invention of the MMR vaccine and its introduction worldwide.

“However, as this study shows non-response rate to the first dose is 5% for those born by natural birth but more than double that when born by a caesarian section.

“Why this could be, it is postulated that the C-section birth results in a different initial microbiome in these babies. And somehow (the paper does not explain why) this may explain the differential response.

“This paper applies to a population where the vaccine is given at a different age than in the UK and supports our policies of giving the vaccine when we do.

“It will be interesting to see if this observation is corroborated by work in other countries and if China changes its timing of MMR vaccine so that the risk of non response is reduced. Presently China has a different age at first vaccination than for example UK or USA, and because of that they have a poorer coverage of risk, however this study may cause a rethink in the public health policy regarding MMR timing.”

Prof Adam Finn, Professor of Paediatrics, University of Bristol, said:

“The authors of this paper have examined antibody levels in two large groups of Chinese infants who had blood samples taken repeatedly during the early months and years of life. They observed that babies born by Caesarian section were more than twice as likely to fail to make an antibody response to the first dose of the measles vaccine. These children did make a response once a second dose of the vaccine was administered. This evidence adds to previous evidence relating to other vaccines which has suggested that babies born by vaginal delivery and/or who are breast fed make stronger or more reliable immune responses. Although the analysis in this paper has been done very carefully, it is important to point out that these are observational data and so prone to bias. In other words, we can’t be certain that the Caesarian delivery is the cause of the lower response rates to the first dose of the vaccine because women who have Caesarian delivery may differ from women who have vaginal deliveries in other ways as well and those differences may be the true cause. Also, if the findings reported were among many other analyses which showed no difference and which were not reported, this increases the possibility that the difference reported occurred by chance alone. Nevertheless, the paper raises important questions that need to be researched further, because many children are born by Caesarian delivery these days and the rates continue to rise. The authors also correctly emphasise that their findings reinforce the importance of the second MMR dose. It is well known that a minority of children do not get protection from measles after one dose and this is the main reason that two vaccine doses are routinely recommended, for all children, not just those born by Caesarian section.”

‘Dynamics of measles immunity from birth and following vaccination’ by Wei Wang et al. was published in Nature Microbiology at 10:00 am UK TIME on Monday 13 May 2024.

DOI: 10.1038/s41564-024-01694-x

Declared interests

Prof Alastair Sutcliffe: I have no conflict of interest with this study.

Prof Adam Finn: “Adam Finn is an unpaid adviser to the UK government and was formerly to WHO concerning vaccine policy, leads research related to vaccines for the University of Bristol which is funded by vaccine manufacturers and does paid consultancy for companies which develop and manufacture vaccines, including some which market measles-containing vaccines.”

For all other experts, no reply to our request for DOIs was received.