As the entire world anxiously awaits the development of a safe and effective coronavirus vaccine, scientists are working to answer a closely related question: how long does COVID-19 immunity actually last?
For some diseases like the measles, immunity often lasts a lifetime. But early data suggests that’s not the case with SARS-CoV-2. Studies from China, Britain, and the United States reveal what we know so far about the behavior of COVID-19 antibodies and what that behavior implies about immunity.
What Are COVID-19 Antibodies?
The body naturally creates antibodies to fight infections. Every winter, for example, the human body develops antibodies to attempt to fight the flu. As soon as antibodies recognize a foreign substance, antibodies stop the pathogens from causing harm. This process of recognizing and eliminating foreign invaders makes antibodies essential to a strong immune system.
Scientists and researchers are extremely interested in the unique properties of the antibodies created in the presence of the coronavirus. By understanding how long those antibodies remain active in the body, researchers can develop reliable COVID-19 treatments and diagnostic tools. They can also predict the future behavior of COVID-19 infections.
What About T-Cells?
T-cells function as the partner in crime to antibodies.
“T-cells are very important in fighting viruses,” explains Dr. Kari Nadeau at Stanford University. “They can kill viruses. And so, one thing we’re looking at [is] as the antibodies wane, do the T-cell responses also wane?”
Scientists are paying close attention to T-cell responses during vaccination development and clinical testing. Many have observed that their experimental vaccines do spark strong T-cell activity.
“We know from many other infections, the vaccine response can be much more durable than the natural infection response,” said Adrian Hill, the principal investigator for the vaccine study through the University of Oxford. “I’m pretty confident that in COVID we’re going to see the vaccines are more durable than a natural COVID infection.”
Recent Studies Reveal Antibody Level Patterns
A Chinese study published in June reported that levels of an antibody correlated to COVID-19 fell sharply only two to three months after infection. This pattern was observed in symptomatic and asymptomatic patients alike.
Another study from a research group at UCLA tracked antibodies in 34 people with the coronavirus. Researchers found that the average antibody levels dropped to half of where they started over a period of about 2 ½ months. This confirms the findings of the Chinese study, although the snapshot is limited to just a few months of activity, rather than years.
Dr. Otto Yang, a lead researcher in the UCLA study, explained that “The majority [of patients studied] just recovered at home with no hospital care, so their antibody titers weren’t extremely high. Indeed, we have seen other people that have very, very high antibody titers, on the order of 10 to 100 times higher than these.”
Based on Yang’s findings, it’s possible that antibody levels vary based on the intensity of the COVID-19 infection a person experiences. But nothing is known for sure, so people who have been infected with the coronavirus must wait and see whether they remain immune, and if so, for how long.