Optimum age for measles immunization in Malaysia.

A study was carried out at the University Hospital, Kuala Lumpur, Malaysia to determine the age-specific prevalence of measles infection by serology and the age specific-seroconversion rates following measles vaccination. The results show that the percentage of children with passively acquired measles antibodies decreased with increasing age till 3 to 5 months of age. From 12 months of age, the percentage of positivity increased sharply due probably to natural infection. The geometric mean antibody titre was low at birth, but from 6 months it started to increase. These results indicate that measles infection is common in Malaysia and a small number of children began to acquire natural measles infection from 6 to 8 months of age; however the peak age for the acquisition of measles infection was from 12 months to 5 years of age. Seroconversion rates following vaccination from 9 months of age, ranged from 94% to 99%. However, the rates and the geometric mean titre were higher among those vaccinated at 11 months of age or older compared with those vaccinated at 9 or 10 months of age. Basing on the above results, it was concluded that the optimum age for measles immunization in Malaysia should be 11 months.