The herd immunity against measles, which protects vaccinated and not vaccinated, is no longer in Portugal due to the decrease in the number of people immune to the disease in the last 14 years.
The data are included in the National Serological Survey (NSS) 2015-2016, developed by the National Institute of Health Dr. Ricardo Jorge (INSA), in which 4,866 people participated, and which updates the last study, related to 2001-2002.
In the previous survey, the seroprevalence for measles virus was 95.2%, but the current survey indicates 94.2% of individuals are immune to the disease.
“This value is less than 95%, the proportion of seropositive individuals [with contact with the infectious agent] required for herd immunity to occur”, which is an indirect effect of vaccination that protects vaccinees, but also those that do not receive the vaccine, since it reduces the circulation of the agent and the transmission of the infection.
We’ve been warning about this for years; it’s sad it’s come to this — I just hope it doesn’t get worse.