Only about 50 per cent of children aged nine months to 15 years in Tamil Nadu have been vaccinated by the measles-rubella combination vaccine since the campaign was launched. Unless and otherwise the vaccination coverage is increased to over 90%, there is a high possibility that the State would witness more rubella infections among older age groups. This would, in turn, lead to an increase in the number of newborns with congenital rubella syndrome (CRS) — hearing impairments, eye and heart defects and brain damage – miscarriage and even infant deaths when women get infected with rubella virus during the early stage of pregnancy.
Paradoxical increase in CRS
“When the rubella childhood immunisation coverage in communities is sub-optimal, there will more number of CRS cases than before as the infection shifts to an older age group. This is called the paradoxical increase in CRS,” says Dr. Jacob John who is co-chairman of the India Expert Advisory Group for measles and rubella. “There will be fewer CRS cases initially (one-three years) after immunisation. But in four-five years, as the infection shifts to an older age group, there will be more CRS cases than before.”
“In order to avoid this we need high coverage during both the campaign and the universal immunisation programme (UIP),” he says. There is a compulsion that the UIP becomes more efficient than before. “The national average for immunisation coverage is 72%. The country and the States have been stagnating. It’s a tall order that all States achieve above 95% coverage. This is an unprecedented requirement for UIP,” says Dr. John.
“The measles-rubella vaccination coverage in Goa is over 90%. In the case of Karnataka it is 87-88%. Tamil Nadu is struggling at 50%,” says Dr. Pradeep Haldar, Deputy Commissioner — Immunisation, Ministry of Health and Family Welfare, Government of India. “Karnataka has been able to handle the crisis of misinformation about the safety of the combination vaccine by adopting several strategies, while Tamil Nadu has been struggling.” As a result, the duration of the campaign in Tamil Nadu was extended by 15 days to cover more children in the nine months to 15 years age group.
“Of the 35 million children targeted in the five States [Karnataka, Tamil Nadu, Puducherry, Goa and Lakshadweep] we have already vaccinated 23 million children. If there were any concerns about vaccine safety we would have already seen it by now. But we have not seen any. So the vaccine is safe and the fear is unfounded,” stresses Dr. Haldar.
Problem with low coverage
Greece and Brazil witnessed the paradoxical increase in CRS due to shift of age distribution of rubella cases. In 1993, a “major rubella epidemic took place [in Greece] affecting women of child-bearing age at a rate higher than in previous years,” says a 1999 paper in the BMJ. Following the rubella epidemic, Greece saw the largest number of babies born with CRS.
In Greece, during the later 1970s and the 1980s, rubella vaccination coverage remained “consistently” below 50% and did not reach 50-60% before 1990. As a result, the proportion of pregnant women susceptible to rubella showed a steady increase — from 12% in 1971-75 to 24% in 1984-89 to 36% in 1990-91.“In 1993, the mean age of patients with rubella was 17 years and 64% were 15 years or older,” says the paper.