The World Health Organisation (WHO) calls this highly contagious viral disease an “important cause of death among young children” globally. But, measles of late is being reported from among adults in Kerala, posing a new public health challenge as the severity of the disease is reportedly higher among grown-ups.
According to doctors, the number of patients seeking treatment for measles in the 1-5 age group is not very high. There are, however, many in the 19-40 age group and those aged below nine months. According to sources, around 600 measles cases are reported in Kerala every year. In 2019, as many cases were reported between January and April itself, a majority of them in Thiruvananthapuram district.
K. Mohandas Nair of the Institute of Maternal and Child Health, Government Medical College Hospital, Kozhikode, says that there can be three reasons for this phenomenon.
Vaccination
The protection supposed to be provided by maternal antibodies, transferred to the child in the womb, is the reason for fixing the first vaccination age for measles at nine months, he says. If the vaccination is given earlier, there is a chance of these antibodies interfering with the immune response to the vaccine, making it ineffective. However, if the child is exposed to the virus present in the community between the age of six and nine months, there is a chance of infection, Dr. Nair says.
“Until recently, only one dose of measles vaccine was being given to children, which ensures an immunity coverage of 90% to 95%. The remaining 5% to 10% people are at risk even after being immunised,” he points out. Also, there are others who deliberately choose not to be vaccinated and get infected.
Immunity loss
Doctors believe that when universal immunisation in childhood is improving, the disease is now moving to an un-immunised older age group or people whose vaccine-acquired immunity is on the wane as the virus is still present in the society. They are also concerned about the increased severity of the disease among adults, with many requiring in-patient treatment and some even being admitted to intensive care units. There have been a few deaths too. Immuno-compromised patients such as organ transplant recipients on immuno-suppressants, patients inflicted with HIV, pregnant women, and cancer patients can be at risk as they might have lost their immunity even if they had been vaccinated.
The motive behind giving the vaccination in two doses, initially at the age of nine months and later between 15 and 18 months, is to address some of the above-mentioned issues, Dr. Nair says. This ensures around 99% of immunity. Also, if there is any measles outbreak in any place, children should be vaccinated even if they are aged six months. Another two doses will have to be given again later. If a sufficient number of people are immune to a particular disease through vaccination, other un-immunised people may get a herd immunity too, Dr. Nair says.
