/Coronavirus antibodies may last just months, mounting evidence shows – Business Insider

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.

Read more: The top 19 coronavirus antibody tests ranked by accuracy, and where to find them

Antibodies may last just a few weeks or months

Detroit tests for antibodies

A young Detroit resident is tested for coronavirus antibodies on April 28.

REUTERS/Rebecca Cook


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.

But the evidence from the June study suggests the time frame might be shorter.

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.

FILE PHOTO: Scientist Linqi Zhang demonstrates work in his laboratory where he researches novel coronavirus disease (COVID-19) antibodies for possible use in a drug at Tsinghua University's Research Center for Public Health in Beijing, China, March 30, 2020. REUTERS/Thomas Peter

A scientist researches coronavirus antibodies at Tsinghua University’s Research Center for Public Health in Beijing on March 30.

Thomas Peter/Reuters


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).

Read more: Dozens of drugmakers are racing to develop coronavirus vaccines. Here’s how they see 2020 playing out and when the first vaccines might be available.

Loss of immunity was most common among people who never developed symptoms, Reuters reported.

“Immunity can be incomplete. It can be transitory. It can last for just a short time and then disappear,” Raquel Yotti, one of the study’s coauthors, said during a news conference.

But Krammer said he was skeptical of the findings.

“It’s physically not possible for antibodies to disappear in a matter of weeks,” he said.

Krammer said the half-life for immunoglobulin (IgG), the most common antibody found in our blood, is one to three weeks. That’s how long it takes for the number of those protective proteins to decrease by half.

“Within weeks, the amount of antibodies you have will be cut in half, not gone,” he said.

We don’t know what level of antibodies protects us from infection

The problem with studying how long antibodies last is that it’s still unclear what level one needs to be considered immune in the first place.

“We do not know how much protection the antibodies may provide or how long this protection may last,” the Centers for Disease Control and Prevention said.

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. 

A recovered coronavirus (COVID-19) patient donates blood samples for plasma extraction to help critically ill patients at the National Blood Transfusion Center.

A recovered coronavirus patient donates blood samples at the National Blood Transfusion Center on June 22.

Ameer Al Mohammedaw/Getty Images


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.”

Novavax Coronavirus Vaccine

A researcher looks at protein samples at Novavax labs on March 20.

Andrew Caballero-Reynolds/AFP


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.

t cell

Scanning electron micrograph of a human T lymphocyte (also called a T cell) from the immune system of a healthy donor.

NIAID


“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. 

Some research has even shown that not everyone who gets sick develops detectable antibodies, which suggests their response to the virus could be tied up in a different layer of the immune system.

But neither recent study of antibodies — in China or Spain — tested participants to see how many T cells and B cells they developed. 

Hilary Brueck, Morgan McFall-Johnsen, and Adam Payne contributed reporting to this story.

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