More than a year into the COVID-19 pandemic, many questions remain about immunity from prior infections and vaccinations.
For instance, how long can immunity last? Do people need to be fully vaccinated if they were previously infected with COVID-19? Do mild and severe infections differ regarding the buildup of antibodies and levels of disease protection? How likely is it for someone to get reinfected?
Health experts are still looking into many of these questions but offer some insight into what they have learned. “Reinfection is relatively rare in people who have recovered from COVID-19, but it can occur. I suspect that people are protected from severe disease for approximately a year or so after natural infection. However, they may be able to contract mild or asymptomatic infections,” said Dr. Amesh Adalja, a senior scholar for Johns Hopkins Center for Health Security.
Protection after the natural infection seems to last at least six to eight months. However, it likely lasts even longer, said Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University.
He added that researchers are still studying how long immunity from infection lasts and are not quite as confident about the proposed yearlong protection time frame with shorter periods. Another uncertainty is how coronavirus variants impact a person’s immunity from a previous infection.
As the coronavirus mutates and more variants emerge, there is some evidence that specific variants, specifically, the beta variant from South Africa, might be able to “overcome natural immunity,” said Dr. Adalja, noting that vaccination is needed to “augment immunity.”
Increasing evidence suggests that those naturally infected by the coronavirus might only need one dose of the two-dose coronavirus vaccines to build up enough immunity.
A recent study by the American Chemical Society found that in participants who had COVID-19 before vaccination, the first dose produced a “vigorous antibody response similar to severe natural infection.” Still, the second dose didn’t provide any additional increase in antibody levels.
One dose of either the Pfizer-BioNTech or Moderna vaccine triggered antibody responses similar to those seen after mild COVID-19 conditions for participants without previous infection. In contrast, two doses started antibody levels comparable to those with severe illnesses. , the Centers for Disease Control and Prevention is actively discussing whether previously infected individuals need to be partially or fully vaccinated, and no official recommendation has been made yet.