Before the availability of a measles vaccine in 1963, every year in the United States measles would cause 2 million to 3 million cases, 48,000 hospitalizations, and 500 deaths, usually from dehydration, pneumonia and encephalitis. But measles virus had another ominous effect. It also caused an increase in the incidence of other bacterial and viral infections several years after the original measles infection. Recently, two studies provided a biological explanation for this observation.

European researchers examined the changes in the frequencies and specificities of memory B cells in 26 unvaccinated children who were naturally infected with measles (Petrova, VN, et al. Incomplete genetic reconstitution of B cell pools contributes to prolonged immunosuppression after measles. Science Immunology. 2019, Nov 1;4(41):6125. DOI: 10.1126/sciimmunol.aay6125) In addition to finding a depletion in memory B cells following natural measles virus infection, the authors also found a depletion of influenza-virus specific memory B cells in ferrets experimentally infected with influenza then later challenged with measles. The monkeys were again susceptible to influenza infection. The authors concluded, “The depleted memory pools and serological immunity highlights the importance of measles vaccination not only to protect against measles but also for the maintenance of immunity to a range of other pathogens.”

Similarly, researchers at Harvard Medical School studied 77 unvaccinated children before and two months after natural measles virus infection (Mina, MJ, et al. Measles virus infection diminishes preexisting antibodies that offer protection from other pathogens. Science. 2019, Nov 1;366(6465):599-606. DOI: 10.1126/science.aay6485). They found that measles infection caused an elimination of 11% to 73% of the pathogen-specific antibody repertoire among those infected. This effect was not observed following vaccination with measles-containing vaccine. The authors concluded, “These findings underscore the crucial need for widespread vaccination … Comprehensive coverage with measles vaccine would not only help prevent the 120,000 deaths that will be directly attributed to measles this year, but, by preventing measles virus immune amnesia and thus preserving immunity, measles vaccines could avert possibly hundreds of thousands of additional deaths attributable to the lasting damage to the immune system.”

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