Coronavirus antibodies may last just months, mounting evidence shows – Business Insider
Among the many lingering questions about the coronavirus, one of the most crucial is: How long do antibodies last?
With some diseases, like measles and hepatitis A, infection is a one-and-done deal. Once you get sick and recover, you’re immune for life.
“For human coronaviruses, that’s not the case,” Florian Krammer, a vaccinologist at the Icahn School of Medicine at Mount Sinai, told Business Insider. “You can get repeatedly infected once your immunity goes down.”
Increasingly, research is starting to coalesce around an unfortunate picture of COVID-19 immunity: People who develop antibodies might not keep them for very long.
Last month, a study showed that antibodies may last only two to three months. Then research published Monday suggested that antibodies could last only three to five weeks in some patients.
Such findings have implications for vaccine development, since the efficacy of a vaccine hinges on the idea that a dose of weakened or dead virus can prompt your body to generate antibodies that protect you from future infection. If those antibodies are fleeting, a vaccine’s protection would be fleeting too.
Short-lived antibodies also diminish hopes of achieving widespread or permanent herd immunity.
In April, Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, hypothesized that people who were recovering from COVID-19 at that time would likely be immune into the fall.
“If we get infected in February and March and recover, next September, October, that person who’s infected — I believe — is going to be protected,” Fauci said.
The researchers tested for antibodies in 37 people who had fallen ill and recovered in Wanzhou, China. They also tested 37 others who had tested positive for the virus but never showed symptoms. About eight weeks after recovery, antibodies dropped to undetectable levels in 40% of the asymptomatic people and in 13% of those who had symptoms.
The most recent research on this topic, however — published this week in The Lancet — suggests that one in five people studied lost detectable levels of antibodies within five weeks.
The study tested 60,000 people in Spain for antibodies three times between April and June. About 7% of the participants who had antibodies during the first phase of the study (April 27 to May 11) no longer had them in the second phase (May 18 to June 1), according to CNN. About 14% of participants who had antibodies during the first stage no longer had them by the third phase (June 8 to 22).
With many better-studied viruses like measles, Krammer said, “you know how many antibodies you need to be protected.”
But we don’t have a specific number for the coronavirus.
Identifying that threshold could be “extremely helpful for vaccine development,” Krammer said — that way, researchers conducting trials would know whether their formula is going to work.
But even if antibodies disappear, that doesn’t mean a vaccine is useless
The point of an effective vaccine is to produce antibodies in enough people to build up herd immunity within the population. To put the coronavirus in decline, at least 50% of the population would have to be immune, perhaps far more.
But it’s not a deal breaker if people become susceptible to reinfection sometime after the initial shot, Krammer said.
“This happens for a lot of vaccines,” he said. “It’s not a problem. You can get revaccinated.”
That’s what booster shots are for. The question, however, is whether follow-up shots will be needed on the scale of months or years.
Your immunity to the virus isn’t solely tied to antibodies
There’s one other reason that the findings about antibody levels dropping shouldn’t cause excessive concern: Your immunity doesn’t just depend on these proteins.
White blood cells also have an impressive immunological memory that can help your body identify and attack the invading virus should it ever return. T cells can destroy infected cells, and B cells work to produce new antibodies.
“If you’re reinfected after some time, it would be an attenuated disease. It will be not as severe as the first time because your B and T cells remember the virus and react quickly,” Krammer said.