Wednesday, December 7, 2016

Measles and Vaccination Failure

Widespread immunization against measles began in the 1980s and the vaccination programme had critical success in preventing spread of this contagious disease. The World Health Organization recommends that all children should be given two doses of the MMR vaccine as part of national immunization campaigns. The Centers of Disease Control and Prevention (CDC) recommends that the doses be separated by at least 1 month and administered on or after the first birthday for all children. Death due to measles has reduced from 5,62,400 deaths in the year 2000 to 1,22,000 in the year 2012. The WHO goal is to eliminate measles globally by the year 2020.

The measles vaccine provides long term and normally lifelong immunity. However, secondary vaccine failure - where the body does develop immunity after two doses of vaccine but still falls prey to measles  has also be reported. A study published in the Indian Journal of Medical Research (2011) examined antibody concentrations in children from Delhi for over a year. The study concluded that four out of five children, who had been given two doses of the vaccine as per the country’s immunization programme, still remained susceptible to contracting the disease, as they had not developed the necessary seroprotection levels. The United States is among other countries that have reported cases of outbreak of measles among vaccinated populations.

The waning immunity of the vaccine has been attributed to several factors. In countries like India with a huge vulnerable population, the first dose of MMR is given when the child is nine months old. At this age, the mother’s antibodies interfere with seroconversion after the vaccination thus affecting immunity. Delaying the first dose to 12 months may prevent the waning of immunity. Secondly, the potency of the vaccine and the conditions under which it is preserved could also pay a role in vaccine failure. The solution to the problem of vaccination failure may thus lie in delaying the first dose, regular surveillance or immunity checks of the vaccinated population and better storage/preservation of vaccines.

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