Protective efficacy of standard Edmonston-Zagreb measles vaccination in infants aged 4.5 months: interim analysis of a randomised clinical trial

According to World Health Organisation vaccination policy, the recommendation for routine measles va...

According to World Health Organisation vaccination policy, the recommendation for routine measles vaccinations is at 9 months. However, a new study finds that an additional earlier vaccination given at 4.5 months may reduce measles outbreaks in developing countries.

The reasoning behind the current policy, is that children born to naturally infected mothers will be conferred maternal antibodies which typically last for the first 9-15 months of the infantƒ??s life. It therefore makes sense that vaccinations are given at 9 months to ensure that children continue to be adequately protected against measles.  However, in the past 20 to 25 years, measles vaccination campaigns have immunised many mothers, who in turn only transfer about half the maternal measles antibodies to their children compared to naturally immune mothers. A similar pattern is seen with HIV when comparing HIV negative and positive mothers. HIV positive mothers transfer fewer antibodies to their children, and HIV positive children lose their maternal antibodies earlier. This has led to a cohort of children who lose their protective maternal antibodies between 3 and 5 months, and therefore require vaccinations at an earlier age.

An analysis of vaccination policies conducted in Guinea- Bissau, Africa revealed that only 28% of children had the necessary maternal antibodies to protect against measles at 4.5 months. However, if these children were vaccinated at 4.5 months, a second blood test taken at 9 months showed that 92% now had measles antibodies. Furthermore, vaccination at 4.5 months of age resulted in a 100% protection against being hospitalised for measles and an over 90% protection against measles infection. Ultimately, results showed that vaccination at 4.5 months and 9 months provided better protection against measles than children vaccinated only at 9 months.

Link to BMJ
Link to Pubmed article