Remarkable progress has been made globally during the past 10 years to reduce measles mortality. By 2008, the annual number of measles associated deaths occurring worldwide had reduced by 78% from 733,000 in 2000 to 164,000 [6]. Sub-Saharan Africa in particular, has demonstrated the impact of increasing routine vaccine coverage while also providing a second opportunity for measles vaccination through measles catch-up campaigns [7]. From 2000 to 2008, measles deaths in Africa declined by 92%. Progress, however, has not been uniform between countries or regions of the world. South East Asia disproportionately accounts for more than three-fourths of the remaining measles deaths globally and the majority of these are in India. It should be noted that prior to 2010, India was the only country in the world that had not introduced a second dose of measles vaccine in its national immunization program [3-5].

Measles vaccination was introduced into India’s Universal Immunization Program in 1985. As per national guidelines, measles vaccine is given to children at 9-12 months of age. Although coverage with single dose measles vaccine has steadily risen over the years, it is estimated to be only 70% nationally [8-10], with considerable variation in coverage both between and within states. The combination of historically low routine vaccination coverage and primary vaccine failure (measles vaccine effectiveness is estimated to be 85% when given at 9 months of age) results in a substantial number of susceptible children in successive birth cohorts which fuels measles virus transmission. A crude but useful calculation demonstrates the number of susceptible children that result each year with successive birth cohorts. With 70% routine measles vaccination coverage and 85% vaccine effectiveness with a single dose given at 9 months of age, real protection to measles is only 60% (0.70 × 0.85=0.60) and thus approximately 40% of India’s annual birth cohort of 26 million children remain susceptible to measles. At this rate, the accumulation of susceptible children in successive annual birth cohorts would reach the epidemic threshold level every 2-3 years [11].

Fig. 1 2nd opportunity of measles vaccine: State specific delivery strategies.

The rationale for providing a second opportunity for measles vaccination is thus two-fold. The immunological rationale is to immunize the primary vaccine failures – those children who failed to respond to the first dose, while the programmatic rationale is to vaccinate those children who were missed by routine services. Most children who have failed to respond to the first dose of MCV respond well to a second dose [12]. MCV2 can be delivered either through existing routine services or through measles catch-up immunization campaigns, the choice is determined by the strategy that would attain the highest levels of coverage. In weak program settings, organized catch-up vaccination campaigns that benefit from specific planning and intense communication and coordination efforts have been proven to effectively achieve high coverage levels in all socio-economic strata [4,6]. Furthermore, numerous studies from a range of development settings have found two doses of measles vaccine to be highly cost effective [12]. In settings of low immunization coverage, the campaign approach has also been found to be more equitable across wealth quintiles [13].

Building on global experience and recognizing that measles represents a significant source of preventable child mortality, the Government of India announced in May 2010 its decision to implement the National Technical Advisory Group on Immunization (NTAGI) recommendation to introduce MCV2 [3,14]. As recommended by the NTAGI, the implementation strategy of MCV2 at the state level is determined by the underlying performance of the routine immunization (RI) program. In total, 14 states with measles coverage less than 80% (Arunanchal Pradesh, Assam, Bihar, Chattisgarh, Gujarat, Haryana, Jharkhand, Madhya Pradesh, Manipur, Meghalaya, Nagaland, Rajasthan, Tripura and Uttar Pradesh) will introduce MCV2 through catch-up vaccination campaigns. In the remaining 21 states with better performing routine immunization systems(i.e., ≥80% routine measles coverage) 17 will introduce MCV2 for children aged 16-24 months through the routine program. The remaining four states and union territories (Delhi, Goa, Puducherry and Sikkim) already use a second dose of measles vaccine in their RI programme (as mumps-measles-rubella vaccine) financed with state resources [15].