Who are the children at risk? Lessons learned from measles outbreaks.

We investigated a measles outbreak in the Jerusalem district in 2007-2008 (992 cases). Most cases (72·6%) were aged <15 years, 42·9% aged <5 years, and 12·8% were infants aged <1 year. The peak incidence rate was in infants aged 6-12 months (916·2/100 000). This represents a significant shift from former outbreaks in 2003-2004, where the peak incidence was in the 1-4 years age group. Of children aged <5 years the proportion aged 6-12 months tripled (7·7% vs. 25·6%). In a case-control study (74 cases, 148 controls) children who developed measles were less likely to be registered in a well-baby clinic and had lower overall immunization coverage. The differences in proportions for registration, DTaP3 and MMR1 coverage were 35·1%, 48·6% and 80·8%, respectively (all P<0·001). Rising birth order of cases and their siblings was associated with non-registration and non-compliance with MMR immunization. The vulnerability of young infants and the risk markers noted above should be taken into account in planning intervention programmes.