A mutated measles virus is responsible for the recent outbreak of that virus that has led to 1000 cases in the São Paulo area, according to Edison Luiz Durigon, a professor at USP's Institute of Biomedical Sciences and one of the country's most respected virologists.
The previous outbreak of the disease, which was considered eradicated in Brazil in the past decade, occurred in 1999. The current version of the virus, however, is another.
Still, the vaccine protects against this type of measles virus, the D-8. But the amount of antibodies in the body of an immunized person (made with the type A virus) drops after 15 years of application.
Therefore, anyone who has never been immunized or injected for a long time should be vaccinated. WHO estimates that from 2000 to 2017, 21 million measles deaths were prevented by the vaccine.
With the amount of antibodies generated by someone who recently took the vaccine, the body can neutralize viruses of various types (8 in all, from A to H) and subtypes (24, distributed between types).
People usually get their first dose of immunization in the first year of life, but a booster is sometimes overlooked, which explains the focus of campaigns on adolescents and young adults.
With few antibodies in the body, the virus can replicate, and some of these people develop the disease. In other cases, even if there are no symptoms, people function as mobile virus factories and spread them by breathing, coughing, and sneezing.
People who lived in the 1970s have probably had contact with the wild virus (the vaccine uses the attenuated version). In this case, the immune memory is stronger and tends to keep the person healthy.
The strategy employed to control the current outbreak is appropriate, says the virologist. As in 1999, babies were immunized from 6 months of age. It would be essential to provide for reinforcements at 15 and 30 years of age.
D-8 viruses circulated generally in Europe and began to pop up about a year ago in Venezuela and the northern part of the country. "Because there were a few cases, we thought the disease was spreading among unvaccinated people."
Translated by Kiratiana Freelon