MEASLES, AN UNDERUSED VACCINE

Monday, 6th of June 2011

GAVI’s mandate includes the provision of new and underused vaccines. It is natural that the London pledging conference will emphasize the introduction of vaccines not currently in use in most developing countries: pneumococcal vaccine, rotavirus vaccine, and HPV.

What about measles? It is not new a new vaccine (FDA licensure was in 1962). It is underused, especially in those countries where the second opportunity to vaccinate is not yet fully implemented. Writing in Indian Pediatrics, John and Choudhury call for adoption by India of two dose regimes, using mass campaigns in the underperforming states with <80 percent routine coverage, and two dose routine schedules in the states with high routine coverage.

If GAVI can spend additionbillionsal on the new vaccines for eligible countries, would not additional millions on measles be a good investment?

Good reading.

Full text of their article, http://www.indianpediatrics.net/nov2009/939.pdf

From ‘Accelerating Measles Control in India: Opportunity and Obligation to Act Now, Indian Pediatrics

Providing a second dose of measles vaccine

The average seroconversion rate with measles vaccination at 9 months is 85% (range 70%-

98%)(9,10). Thus, approximately 15% of vaccinated children remain susceptible in spite of receiving one dose. As the level of ‘herd immunity’ needed to significantly impact measles transmission is in the range of 93-95%, even 100% coverage with a single dose of measles vaccine administered at 9 months of age will not prevent the accumulation of a susceptible pool and consequent periodic measles outbreaks. Seroconversion rate improves to >95% when the vaccine is given after one year of age, but the first dose has to be given earlier to protect infants.

Field investigations of recent measles outbreaks in developing countries have found that, while some cases occurred in previously vaccinated children (i.e., vaccine failure), most cases occurred in unvaccinated children, indicating that program failure was the predominant reason. For these reasons, WHO and UNICEF recommend that all national immunization programs provide 2 doses of measles vaccine for all children(11). The purpose of the second dose is to protect children who received their first dose but failed to respond. In addition, the second opportunity

provides one dose to those who missed the first dose.

In settings with low to moderate routine vaccination coverage (<80%), SIAs are the preferred method of delivering the second dose, as they usually achieve coverage levels of >90%. SIAs reach children who lack access to health services, and have been shown to rapidly reduce measles incidence. In settings with high routine vaccination coverage (i.e., ≥80% for 3

or more consecutive years), the second dose may be delivered through routine services(12).