Chances Are, You'll Get Covid-19 Again

"There's a good chance you'll get Covid more than once.

Covid-19 reinfections are more common and can happen within a shorter window of time than doctors previously thought possible, recent research suggests. More than half of people in the U.S. showed signs of having been infected at least once as of February, according to a report Tuesday from the Centers for Disease Control and Prevention.

Data from the U.K. government found that reinfections were 10 times higher during the recent Omicron outbreak compared with the earlier Delta outbreak between May and December last year. People who were unvaccinated, younger and lived in areas the study described as more deprived were more likely to be reinfected between July 2020 and March 2022.

Reinfections usually appear to be mild in otherwise healthy people, doctors say. But some reinfections are serious, and it's not clear what the risk of long Covid might be. People who had a milder first infection with a lower viral load were at higher risk of being reinfected, the U.K. data indicate.

"On average at a population level, the people who get reinfected have milder symptoms," says Francois Balloux, an infectious disease epidemiologist and director of the UCL Genetics Institute in London. "That doesn't mean that some people might not have a worse infection the second or even third time."

Currently in the U.K. about 12% of Covid-19 infections are reinfections, Dr. Balloux says. He expects that number to increase over time and says that it's likely that the viral dose or number of particles a person is exposed to will influence the symptom severity.

Scientists are still learning about the frequency and severity of reinfections; much of the research is preliminary so far. The U.S. doesn't track national reinfection rates broadly.

Reinfections can happen within less than 3 months

Doctors and health agencies typically say most people are protected from a Covid reinfection for at least 90 days. Your body's immune defenses typically strengthen after an infection, then wane.

However, there is evidence that people can get reinfected within shorter periods.

An April CDC report identified 10 people who were reinfected with Covid-19 less than 90 days later. In at least one case, reinfection occurred 23 days later.

Researchers in Spain recently presented preliminary results of a study documenting the case of a 31-year-old woman who caught Covid-19 twice within three weeks. The woman, a healthcare worker, was fully vaccinated and received a booster shot 12 days before testing positive for the Delta variant on Dec. 20. She didn't develop any symptoms the first time she was infected. Twenty days later, she developed a cough and fever and tested positive for the Omicron variant.

There is also preliminary evidence that reinfections with the same variant can occur. A Danish preprint, a study that hasn't been peer-reviewed, found that reinfection of different subvariants of Omicron are rare but do take place. Among 187 reinfection cases, 47 were people infected with BA.1 and then BA.2 20 to 60 days later, researchers found. The majority of people were young, unvaccinated and had mild symptoms. There was no difference in severity between their first and second infection.

Reinfections can be serious

A March preprint looked at more than 300,000 Covid-19 patients in the U.S. VA system. About 9,200 of them tested positive again at least 90 days after their first positive test; 17% of the reinfected patients were hospitalized. An additional 189 cases had a third positive test at least 90 days after their second infection and about 26% of them were hospitalized.

"There's a lot of reinfection going on in less than 90 days," says Mark Pandori, director of the Nevada State Public Health Laboratory and an associate professor of pathology at the University of Nevada, Reno. Dr. Pandori and colleagues have documented two cases that were significantly more severe the second time around.

Long Covid risk is unclear

Scientists don't yet know what the risk of long Covid is after a reinfection. Amesh Adalja, an infectious-disease physician and a senior scholar at Johns Hopkins University Center for Health Security, speculates that you're less likely to get long Covid after a reinfection -- just as vaccines reduce the likelihood of long Covid -- because the immune system activates faster the second time around.

"The first infection is the one most likely to lead to complications based on what we know with many other endemic respiratory infectious diseases," he says.

But Amy Duckro, an infectious-disease specialist with Kaiser Permanente, says many questions about long Covid remain unanswered.

"I don't think we should make any bets on someone who has a reinfection having a less likelihood of having long Covid," says Dr. Duckro." [1]

1. Chances Are, You'll Get Covid-19 Again
Reddy, Sumathi.
Wall Street Journal, Eastern edition; New York, N.Y. [New York, N.Y]. 28 Apr 2022: A.11.