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.