The measles virus is one of the most contagious viruses causing human disease. For millennia, this virus has been a leading cause of childhood morbidity and mortality, until the development of the measles vaccine in 1963. Since the widespread availability of the measles vaccine, the number or measles related deaths have plummeted. Vaccination has caused a drop in measles deaths from 761 000 in 2000 to 128 000 in 2021.
Measles is spread by contact with infected nasal or throat secretions (coughing or sneezing) or breathing the air that someone with measles has coughed out. This is particularly relevant, because the virus can float in the air for up to 2 hours. It is easily spread by aerosol droplets and remains contagious on infected surfaces for up to two hours.
Deaths quoted as measles deaths are deaths that were recognized as directly related to infection with the measles virus. Most of these deaths are from infections of the respiratory and gastrointestinal tracks. Deaths from direct measles virus infection, such as measles virus pneumonia and encephalitis, occur less frequently. This inherently means that measles related deaths are prone to underestimation; because, seemingly unrelated, and at times fatal infections, can occur as a result of measles infections. This phenomenon is increasingly recognized around the world and is the result of “immune amnesia.”
When we are infected by germs, the immune system takes note of these disease-causing germs and keeps a record of these germs in memory B and T cells. This protects us if we become reinfected with the same germs. If that happens, the body can respond immediately to eliminate the germs on exposure. This is called immunity to that particular germ. If those memory cells are not there, we would be susceptible to the same germs again and again, precipitously increasing the chances that we will eventually succumb to the disease. This is exactly what happens during a measles infection.
To cause infections, the measles virus must bind to the CD150 receptors on cells in our bodies. It so happens that memory B and T cells are especially rich in these receptors. The measles virus therefore infects and destroys our memory cells, making us once again vulnerable to infections that we previously were protected against. This is called immune suppression, because both the diversity and the absolute number of these critical immune cells are decreased.
Evidence of this is seen in the phenomenon of the disappearing Mantoux or tuberculosis skin test, which can become negative after a measles infection, only to become positive again at a later point in time. Further proof of this is seen in the remission of autoimmune diseases, which at times can be long-lasting, demonstrating the long-term effects of measles infections.
When we are vaccinated against the measles virus, we are protected against measles virus infection and the catastrophic destruction of important parts of the immune system. Without the measles vaccine, we are exposed to infection with the measles virus. This leases us vulnerable to infections by multiple germs the body “forgets” how to fight. And to regain the memory lost, scientists estimate it could take 3-5 years. For young children, this can be a matter of life and death.
Proof of the effectiveness of the measles vaccine is in the numbers. Numbers that, because of the phenomenon of “immune amnesia” described above, are grossly understated. Recognition of “immune amnesia” and the hundreds of thousands of excess deaths caused by measles infections provides unquestionable proof of the benefits of measles vaccination.