More than 33 million people in the U.S. contracted COVID over the last year, and for the many survivors, that means some protection from getting infected again. Research over the last year has shown that people who had COVID typically develop some level of immunity against the virus through antibodies and other factors, potentially long after they've recovered from their illness. The question of how long, however, has remained a major point of contention. Now, new research has found some answers: About 88 percent of people who had COVID maintain antibodies for at least 10 months after initial infection.
A study published May 24 in EClinicalMedicine, a Lancet journal, analyzed nearly 40,000 people who were infected with COVID for up to 300 days after infection. The researchers from LabCorp tested participants for antibodies that protect against two different SARS-CoV-2 proteins—nucleocapsid and spike proteins—between March 2020 and Jan. 2021.
According to the study, the antibodies guarding against the SARS-CoV-2 spike protein lasted the longest at the most stable rate. Nearly 88 percent of COVID patients appeared to maintain strong levels of these antibodies for up to 300 days, or 10 months, after they were infected. But 68 percent also showed strong levels of antibodies protecting against the nucleocapsid protein 293 days after infection.
"Our observational analysis provides an encouraging timeline for antibody development and sustainability among the U.S. population," lead author David Alfego, PhD, Labcorp senior data scientist, said in a statement.
Brian Caveney, MD, chief medical officer and president of Labcorp Diagnostic, said in a statement that while this is "good news for naturally infected individuals," further research has to be done so scientists can fully understand what type and level of antibodies allow for protection from COVID reinfection.
"It's important to note that the presence of antibodies doesn't necessarily indicate immunity for this duration. More research is needed to discover quantifiable thresholds of the antibodies' ability to fight the virus—known as neutralizing capacity—in order to understand how long they can perform this work," Caveney told BioWorld.
This is why the Centers for Disease Control and Prevention (CDC) still recommends that those who have been naturally infected with COVID get vaccinated against the virus. "Experts do not yet know how long you are protected from getting sick again after recovering from COVID-19," the CDC says. "Even if you have already recovered from COVID-19, it is possible—although rare—that you could be infected with the virus that causes COVID-19 again."
However, Caveney said the study does give researchers more information so they can continue thinking about how to safely emerge from the COVID pandemic. And it will also allow scientists to make decisions about "future vaccinations and the timing of booster shots," Caveney said.
Those under the age of 65 were more likely to maintain positive rates of these antibodies over time, according to the study. So whether vaccinated, naturally infected, or both, people 65 and older may have a harder time maintaining antibodies to protect against COVID for a prolonged period of time—meaning they may be even more in need of booster shots. Thankfully, Pfizer just started to test COVID booster shots in fully vaccinated individuals over the age of 65.