How Long Does COVID-19 Immunity Last?

The biggest question on everyone's mind lately is "If I get COVID will I become immune to it?"

Two studies show that once an individual develops immunity or antibodies to the COVID-19 virus, they have a strong T cell response to it. The data is "encouraging" according to virologist Angela Rasmussen of Columbia University. The studies don't have enough data to determine whether people who recover after a COVID infection are guaranteed protection in the future, but the findings "bode well," says Rasmussen. 

Antibodies are created when someone contracts various coronaviruses, but the level of antibodies that protect against future occurrences can be spotty according to Dr. Stephen Russell in a recent Myeloma Crowd Radio show. He noted that vaccines can enhance the response of these antibodies. There are over 100 vaccines now in development for COVID-19. 

A team of immunology researchers at the La Jolla Institute for Immunology predicted which proteins could produce the most powerful T cell responses. Then they took immune cells from patients with mild COVID cases and tested them against the proteins. They saw strong immune responses in the samples according to the study authors:

“If we had seen only marginal immune responses, we would have been concerned,” says Sette, a professor in the Center for Infectious Disease and Vaccine Research, and adds, “but what we see is a very robust T cell response against the spike protein, which is the target of most ongoing COVID-19 efforts, as well as other viral proteins. These findings are really good news for vaccine development.”

“All efforts to predict the best vaccine candidates and fine-tune pandemic control measures hinge on understanding the immune response to the virus,” says Crotty, a professor in the Center for Infectious Disease and Vaccine Research. “People were really worried that COVID-19 doesn’t induce immunity, and reports about people getting re-infected reinforced these concerns, but knowing now that the average person makes a solid immune response should largely put those concerns to rest.”

A second study by immunologist Andreas Thiel of the Charité University Hospital in Berlin and colleagues confirmed these findings. The T cells targeting that same spike protein was found in 83% of patients hospitalized with COVID-19. Interestingly, they also found that 34% of uninfected people in the study had helper T cells that recognized the COVID-19 virus. They believe this could be caused from a prior exposure to the common cold or other common past coronaviruses. 

The studies didn't test whether people who have had prior coronaviruses would be more immune to the current COVID-19 version. The new findings showed that T cells react to several viral proteins, which means that new vaccines in development can be designed to go after multiple targets. 

The studies begin to address the role of T cells in combating COVID-19 and how those T cells spark an immune system reaction. The findings don't necessarily mean that people who have recovered from COVID-19 are protected in the future from getting it again, but there is more information and more hope:

“We have a solid starting foundation to now ask whether there’s a difference in the type of immune response in people who have severe outcomes and require hospitalization versus people who can recover at home or are even asymptomatic,” adds Sette. “But not only that, we now have an important tool to determine whether the immune response in people who have received an experimental vaccine resembles what you would expect to see in a protective immune response to COVID-19, as opposed to an insufficient or detrimental response.”