Measles spreads across all age groups in Kerala; experts call for rethink on disease study

A significant surge in measles cases is being observed across various districts of Kerala. The spread has been particularly prominent in Kozhikode, Malappuram, and Palakkad districts. In view of this situation, public health experts have demanded a detailed reassessment of the disease's epidemiology, as the nature of the illness appears to have undergone a notable shift over the years.

Measles was once a disease that primarily affected children between the ages of one and five, but it is now being observed across all age groups. This includes fully vaccinated individuals and infants under nine months of age, who are not yet eligible for regular vaccination.

According to the Integrated Disease Surveillance Programme, 824 confirmed and 1,681 probable measles cases have been recorded in the state as of November 6. Five measles-related deaths have been reported, although only one death has been confirmed so far. It is noteworthy that there was also a major spike in cases during 2022-23.

The measles vaccine was introduced into the Universal Immunisation Programme (UIP) in 1985, with one dose administered at nine months. To bridge immunity gaps following the first dose and to achieve disease eradication, a second dose at 18 months was introduced in 2010. The nine-month limit was maintained so that antibodies transferred from the mother via the placenta would not interfere with the response to the vaccine.

K.K. Purushothaman, former Professor of Pediatrics at Thrissur Government Medical College, stated, "In the recent outbreak, we have seen many infants contracting measles before nine months, possibly because the level of measles antibodies in the current generation of mothers is low. Moreover, cases have also been seen in older adults." He suggested that the state should consider administering an additional dose of the vaccine for women during adolescence or before marriage under the UIP. He has advised the State Technical Advisory Group on Immunisation to examine this proposal and conduct a serological study to determine protective antibody levels in adolescent girls and young women.

This concern is supported by facts from other locations. According to a report by The Hindu, during a major measles outbreak in Mumbai in 2023, more than 31% of cases were among infants under nine months. A study revealed that only 66.8% of mothers had sufficient antibodies to protect their infants.

A World Health Organization (WHO) report published in Vaccine in May 2025 acknowledged that women who acquired immunity through vaccination rather than natural infection may transfer lower levels of antibodies to their children. However, experts concluded that evidence is insufficient to change the recommendation for the first regular dose at 9-15 months.

In a study conducted by the Rajiv Gandhi Centre for Biotechnology (RGCB) on 684 children aged 4 to 18 years in Kerala and Tamil Nadu who had received at least two doses of the vaccine, 8.5% of the children lacked protective antibody levels. According to this study, published in JAMA Network Open in August 2025, 89 children (13%) were measles-specific IgM positive, indicating recent infection or breakthrough infection. Among these, antibody responses varied even though 435 children (63.6%) had received a third dose and seven children had received a fourth dose.