The authors of a recently published observational study have found evidence that a child’s overall chance of survival is improved if the last vaccine they received was for measles.
The researchers analysed routine vaccination and survival data for more than 38 thousand children over a 17 year period in northern Ghana. They looked at children who had received the third dose of the diphtheria-tetanus-pertussis combined vaccine (DTP3) and compared the survival rates of those who had received the measles vaccine afterwards and children that had either missed the measles vaccine or had not been vaccinated at all.
They calculated that during the first year of follow-up, after assessment of vaccination status, there was a 38 per cent reduction in child mortality for those children who had been given the measles vaccine compared to those who were not vaccinated.
When the researchers adjusted their analysis to exclude children who had died of measles, the difference in survival between the two groups remained. This suggests that the measles vaccine may be protecting against more than just the disease it was designed for.
“Evaluations of immunisation programs are usually based on the assumption that vaccines only protect against specific diseases,” said the study’s lead author, Dr Paul Welaga from the Navrongo Health Research Centre in Ghana. “Our new study adds to growing evidence that, when administered in the recommended sequence, measles vaccination helps to reduce child mortality through non-specific effects as well.
In their paper the authors did point out that their calculations may be influenced by differences in access and local improvement of health-care services, but they felt this was unlikely to account for all the excess mortality associated with the children who did not get the vaccine. They pointed out that survival gap between the vaccinated and un-vaccinated children was still present in communities with and without nurses and the gap disappeared after general measles vaccination campaigns in these areas.
Dr Welaga said: “It may be that measles infection is eliminated in the near future and thus measles vaccination is de-emphasized — but if the non-specific beneficial effects of measles vaccination are indeed positive then we should consider continued vaccination even if measles is eradicated.”