The Exchange

Commentary and Observations from
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Measles and Immunity

Measles and Immunity

Measles is a highly contagious viral illness, currently targeted for eradication given the favorable biologic characteristic that humans are the only reservoir. However, due to social and political factors, as well as high transmissibility, elimination has been achieved in very few areas of the world. It remains a significant cause of death worldwide, despite the availability of a safe and effective vaccine. The attack rate in a susceptible individual exposed to measles is 90%. Transmission is airborne as well as via person-to-person contact. Infected individuals are considered contagious from 4 days prior to rash onset until 4 days after rash eruption. Infectious droplets from respiratory secretions of a patient with measles can remain airborne for up to 2 hours. Therefore, the illness can be transmitted in public spaces, even in the absence of person-to-person contact.

Most people who contract the measles virus recover fully. Approximately 30% experience one or more complication. Some of these complications, such as pneumonia and encephalitis, are life-threatening. The risk of complications is higher in the following groups:

  • Children <5 years
  • Adults >20 years
  • Pregnant women, or those who have experienced pregnancy complications
  • Persons with a weakened immune system
  • Individuals who are malnourished
  • Persons with vitamin A deficiency
  • Blind persons
  • Individuals with subacute sclerosing panencephalitis

Natural measles infection is thought to confer lifelong immunity. Immunity due to vaccination is also highly protective against clinical infection. A recent study shows that measles can destroy between 20%-50% of an individual's disease-fighting antibodies, depleting their previous immunity and requiring their body to "relearn" how to protect itself against infection. The study details the mechanism and scope of this measles-induced "immune amnesia." By protecting against measles infection, the vaccine prevents the body from losing or "forgetting" its immune memory and preserves its resistance to other infections. These findings underscore the importance of obtaining measles vaccination, and suggests that those recently infected with measles may benefit from booster shots of all previous vaccines.

An estimated 120,000 deaths will be directly attributed to measles this year alone, and hundreds of thousands more will die from its long-term, immune-related effects. Given the availability and proven effectiveness of the measles vaccine, encouraging vaccination against the disease is a no-brainer.

References
  • Harvard Medical School. How measles wipes out the body's immune memory: study details the mechanism and scope of measles-induced immune amnesia in the wake of infection. www.sciencedaily.com/releases/2019/10/191031204630.htm . Accessed November 19, 2019.
  • Mina MJ, Kula T, Leng Y, Li M, et al. Measles virus infection diminishes preexisting antibodies that offer protection from other pathogens. Science. 2019;366:599-606.

Filed under: Allergy/Immunology, Infectious Diseases

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