That's reminiscent of a 1990 United Kingdom study in which volunteers were deliberately exposed to a coronavirus that causes the common cold. Most of the participants who were exposed twice still got infected again, but they didn't develop symptoms or shed virus for as long as they did the first time — which presumably means they were less infectious.
"We don't know whether that can be extrapolated to SARS-CoV-2, but that would be a good scenario," said Alessandro Sette, a researcher at La Jolla Immunology.
Sette and colleagues recently looked at the immune responses of 185 people who recovered from COVID-19. Their study, which has not yet gone through scientific peer review, showed that most of these people's immune responses were still detectable six to eight months after they got sick.
"We don't see any 'red flags,'" Sette said. "From what we're seeing, it's not hard to imagine that the response could last years."
The findings fit with those of a study that tracked more than 12,000 U.K. health care workers from April to November. Workers with antibodies against the coronavirus, a sign they'd had COVID-19 before, were less likely to get infected than those who'd never been exposed before.
That suggests that antibodies, immune proteins that grab onto the surface of a virus and can prevent it from entering your cells, could reduce the likelihood and severity of reinfection. But not all antibodies block infection, and there's evidence that T cells, which kill infected cells before they can spew out virus, also play a key role in fighting back the coronavirus.
Only time will tell how long immune responses to COVID-19 last — either due to natural infection or a vaccine. Pfizer and Moderna recently reported that their vaccines are about 95% effective in preventing COVID-19, with AstraZeneca announcing its vaccine was about 70% effective overall.
An ideal vaccine would reduce your risk of reinfection for years, even decades. It would also limit your symptoms and make you less contagious if you get infected. But Sette says it's too early to know how well a COVID-19 vaccine would do any of those things, and for how long, though current signs are encouraging.
"The prudent and responsible thing to do is to still adhere, to wear your mask and practice social distancing," Sette said.
Another reason not to throw caution to the wind after recovering from COVID-19: Most people have not been exposed to the virus yet. So even if a second exposure doesn't get you sick, you could spread the virus to someone who's more vulnerable because they don't have immunity.
At the moment, there's a lot of viral spread going around.
"In terms of the most pressing issues today, it's perhaps not as much reinfection as much as it is infections," Sette said. "But clearly they do exist."(c)2020 The San Diego Union-Tribune Distributed by Tribune Content Agency, LLC