The vaccine challenge (SUNDAY PACKAGE LEAD)
C. Maya
THIRUVANANTHAPURAM: As Kerala joins the national campaign for measles-rubella (MR) vaccination, with the goal of eliminating measles and controlling rubella or congenital rubella syndrome (CRS) by 2020, the Health Department seems to be dealing with a dual task – they have to convince general public about the rationale for launching the campaign on one hand, while on the other, they have to defeat the negative propaganda launched by the anti-vaccination lobbyists against the campaign.
Despite the availability of a vaccine, measles continues to be an important cause of morbidity and mortality in the country. Even in Kerala, many do not even consider it to be a serious disease and are unaware of the serious complications of the disease such as meningo-encephalitis. rubella, on the other hand is a mild self-limiting infection which manifests itself with low-grade fever and rashes. While both adults and children are largely unaffected by rubella, the consequences can be devastating for women if they contract the infection in early pregnancy.
rubella infection in pregnant women can result in infants born with congenital rubella syndrome (CRS), a group of severe birth defects such as cataract, hearing deficiency, mental and physical growth retardation and serious congenital heart defects. The CRS risk is at the highest during the first trimester of gestation but, unfortunately, the infection often goes unnoticed because even rashes may not surface in some cases. Elimination of rubella infection assumes a lot of importance as one of the prime strategies for preventing congenital deformities, paediatricians point out.
Since 2007, thanks to the robust measles surveillance network in the State, undertaken as part of the WHO-National Polio Surveillance Project, all cases of fevers with rashes, cough or conjunctivitis are picked up and investigated. In 2016 too, 42 measles/rubella outbreaks were reported in the State, resulting in 1,627 cases of measles or rubella, including four deaths. In the absence of a CRS registry, there is no clear data on the true burden of CRS in Kerala or in the country. However, systematic reviews of various studies have reported that 10-50% of children with congenital anomalies in India have laboratory evidence of CRS.
A study conducted among 250 adolescent girls in Mavoor in Kozhikode district found that 68.3% of the children had already acquired life-long immunity against rubella through previous and undetected childhood infections. This also meant that about 30% of children may remain susceptible to future rubella infections into adulthood and pregnancy. (The study, “Prevalence of rubella-specific IgG antibodies in unimmunized young female population”, appears in the September 2016 issue of the Journal of Family Medicine and Primary Care. )
According to the WHO, even when the susceptibility levels in women are below 10%, there is a chance of CRS in the future. Previous studies from Kerala had reported the rate of acquired rubella infection during pregnancy in the State to be 3%. Considering the fact that the State has, on an average, five lakh deliveries annually, about 15,000 cases of rubella infections among pregnant women and proportionate CRS should be expected in the State annually, the study has found.
The strategy of the World Health Organisation (WHO) for the elimination of measles and rubella says that all infants be administered the MMR vaccine, while special precaution be taken to ensure that all girls in the post-pubertal or marriageable age (who might not have received MMR vaccine in infancy) are protected by a dose of monovalent rubella vaccine.
At present, at the national level, measles vaccine is administered to children at 9-12 months and a second dose at 16-24 months. The current MR vaccination campaign is the first time that the Union Health Ministry is introducing rubella vaccine in its Universal Immunization Programme (UIP).
However, Kerala had on its own introduced rubella vaccination in the State in 2014. Under the State Initiative on Disabilities, as part of a larger initiative to prevent childhood disabilities due to CRS, the State had launched a campaign to vaccinate adolescent girls (classes VIII-XII) against rubella. Alongside, it also replaced the second dose of measles vaccination given at 18 months to infants with MMR (mumps-measles-rubella) vaccine, so that all children are protected against measles and rubella. Though the campaign was not entirely successful, a good cohort of young girls was covered against rubella under the programme.
The national campaign’s strategy is to give one universal dose of MR vaccine to all children, boys and girls, from nine months to 15 years, regardless of their previous vaccination status. Following this, the MR vaccine will be introduced in the national immunisation schedule to replace the single dose of measles vaccine given at 9-12 months and again at 16-24 months. This wide age range campaign, as recommended by National Technical Advisory Group on Immunisation, will rapidly build up immunity for both measles and rubella and reduce the transmission of both diseases in the community.
In Kerala, one universal dose of MR vaccine will be administered to 76.55 lakh children in the targeted age group. The MR vaccine has been found to be highly safe. Vaccination results in high (>95%) seroconversion rates, affording life-long protection against both measles and rubella. As both rubella and measles are highly infectious diseases, at least 95% MR vaccination coverage is required for the State to achieve elimination. The single dose of rubella vaccination which was given to adolescent girls has currently been frozen by the Health department, in the wake of the MR national campaign. After the campaign, the single measles dose at 9-12 months would be made MR vaccine as per the national strategy. However, the State will retain the MMR vaccine it is currently giving as the second dose at 16-24 months. Ultimately, Kerala will have one MR and one MMR dose in its immunisation schedule.
(EOM)
