Herd immunity has been one of the key topics amid the coronavirus pandemic. Previous reports show that when a large proportion of the population gets immune to the novel coronavirus, through vaccination, herd immunity can be achieved.
A study in Spain, however, casts doubt on the prospect of herd immunity as a way to combat the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes the coronavirus disease (COVID-19).
What is herd immunity?
Herd immunity or community immunity happens when a high percentage of the community becomes immune to disease through vaccination or becoming infected with the virus. As a result, it makes the spread of the disease from person to person unlikely, providing people who are not vaccinated, such as newborns and those who are immunocompromised, some form of protection against the pathogen.
Vaccines help prevent many deadly and dangerous diseases. In some countries, for example, like the United States, polio and smallpox have been eradicated due to vaccination. However, some people may not be administered vaccines since they might pose a health threat, such as pregnant women, newborn babies, and those who have weak immune systems.
When many people, about 70 to 90 percent of the population, receive the vaccine or become immune to the virus, they help protect those who cannot receive the vaccine. This is termed as herd immunity.
Not feasible
Spain is one of the hardest-hit countries by the COVID-19 in Europe, and serological surveys have been essential tools to determine the magnitude of the outbreak. Since there are many asymptomatic carriers and limited access to diagnostic tests, serological surveys or antibody testing can help provide a picture of the extent of the COVID-19 spread in the country.
“By contrast, a population-based seroepidemiological survey can quantify the proportion of the population that has antibodies against SARS-CoV-2. A seroepidemiological study provides information on the proportion of the population exposed and, if the antibodies are a marker of total or partial immunity, the proportion of the population that remains susceptible to the virus,” the team explained.