• February 9, 2023

Only 50 people are known to have contracted COVID-19 more than once — but new strains have medical experts on high alert

It is very rare for someone to contract the coronavirus, which causes the disease COVID-19, a second time. However, the few confirmed cases of re-infection indicate that immunity to the virus is not guaranteed and that vaccination could become an integral part of our medical care for the future.

There are approximately 50 confirmed cases of reinfection worldwide. That’s far less than 1% of the 110 million coronavirus cases reported worldwide. BNO News, a Dutch news site, tracks reinfections on a global basis. it is identified 51 confirmed cases of reinfection and around 11,000 suspected or probable reinfections.

Reinfection is believed to occur when protective antibodies decline in people who have previously been infected with the virus or in people who have become infected with the virus without developing antibodies.


“I don’t think anyone had any expectation that if you had COVID and got over it, you could never get it again.”

– DR. Bruce Polish, NYU Langone

For some doctors with infectious diseases, this is no surprise.

“I think everyone expected that there would be renewed infections at some point after the initial infection,” said Dr. Bruce Polsky, an infectious disease doctor at NYU Langone Hospital on Long Island. “I don’t think anyone had any expectation that if you had COVID and got over it, you could never get it again.”

The Centers for Disease Control and Prevention define reinfection as a positive COVID-19 test performed at least 90 days after an initial positive test. (This is used to differentiate people with persistent “long COVID” symptoms.) Health officials say reinfection is rare. However, it is also expected that the number of new infections will increase as the pandemic progresses.

“It is expected that the likelihood of re-infection with SARS-CoV-2 will increase with time after recovery from the initial infection due to waning immunity and possibly genetic drift.” the CDC said in October.

If the pandemic enters its second year, it could put some of the roughly 27 million people in the US who have already had COVID-19 at risk of getting it again.

The length of the pandemic in connection with the appearance of the new, more infectious variants B.1.1.7 and B.1.351 can also increase the risk of a second infection with the SARS-CoV-2 virus. The CDC has indicated the B.1.1.7 strain which has been confirmed in 1,523 Americans as of February 16, could become the most dominant form of the virus in the US by the end of March. The variant B.1.351, which was identified for the first time in South Africa, was detected in 21 people in the USA

“If [B.1.351] The experience of our colleagues in South Africa shows that even if you were infected with the original virus, there is a very high rate of reinfection, to the point where a previous infection does not seem to protect you from re-infection. “Dr. Anthony Fauci, medical advisor to President Joe Biden and longtime director of the National Institute for Allergies and Infectious Diseases, said CNN earlier this month.

What medical research is telling us about immunity

Reinfection studies to date have had mixed results. (Recently a number of projects addressing reinfection were announced, including: one at Indiana University School of Public Health in Bloomington to assess COVID-19 reinfection in US hotspots and one Observational study that plans to evaluate all reported reinfections in France.)

A current preliminary study The Marine recruits studied, who arrived at a base on Parris Island in South Carolina, found that previous infection with SARS-CoV-2 protected them from re-infection – but only to a certain extent. Marines with lower IgG antibody titers and neutralizing antibodies were at higher risk of re-infection, the researchers concluded.

Other research underscores the rarity of reinfection. Researchers in Qatar found that out less than 1% Of the approximately 44,000 people who had recovered from a case of COVID-19, they contracted SARS-CoV-2 a second time.

In addition to the risk of re-infection, there are a number of factors that can affect immunity to the SARS-CoV-2 virus.


“Since you don’t know how long immunity will be induced, the chances are the virus may continue to mutate and actually mutate into a cold virus. We really hope so. ‘

– Dr. Stanley Perlman, University of Iowa

Not all people who become infected with the virus develop antibodies to it, and some people have antibody levels that aren’t high enough to protect them.

It is also unclear how long antibodies remain. COVID-19 antibodies decrease in most people after 60 days, so a CDC study of frontline healthcare workers in 12 states and another study the same group in Nashville, Tenn., although including other studies one Research by healthcare workers in the UK has found that IgG antibodies can last for six months or more.

“Since you don’t know how long immunity will be induced, the chances are the virus may continue to mutate and actually mutate into a cold virus,” said Dr. Stanley Perlman, Professor of Microbiology and Immunology at the University of Iowa. “We really hope so.”

If so, the virus could be blunted into simply becoming an annoying, but no longer fatal, common cold. Colds, which are coronaviruses that have not been eradicated, can provide immunity for up to three years. People who were infected with SARS or severe acute respiratory syndrome, also a coronavirus, had about three years of immunity.

“Sterilizing immunity” is a term used to explain a type of immunity, which means that humans cannot get a virus or the disease caused by a virus. That will most likely not happen with SARS-CoV-2. Experts like Perlman are now wondering whether reinfections cause less severe forms of the disease or are asymptomatic.

“This could be exactly what happens to people who have a mild illness and then get infected again with a serious illness,” Perlman said. “I think the protection is much longer. So if someone comes out of an intensive care unit and is otherwise normal, I think they will be protected for years. “

What we know about reinfection rates in the US

The federal government does not track new infections, so the number of new infection cases in the US is unknown. The side on the CDC website with information on new infections was last updated on October 27th.

Some states have provided details of likely or confirmed reinfections upon request.

In California, for example, two confirmed cases of reinfection are listed among the 3.3 million people there who tested positive for the virus, according to the state’s Department of Health. About 615 people in Colorado meet the CDC criteria for re-infection, according to a state spokesman. “This is a very small percentage of all cases,” she said in an email, which is an estimated 0.15% of all cases in Colorado. There are 716 suspected reinfections and one confirmed case in Washington state.

The first documented case of reinfection in the United States occurred in Reno, Nevada, according to a 25-year-old man study published in the Lancet Medical Journal in October. The person tested positive in April, had two negative tests in May, and tested positive again in June.

His case was identified as part of a genome sequencing program set up in Nevada during the pandemic. (The only way to confirm re-infection is to sequence both samples to make sure they have different mutations that occur naturally as the virus spreads from person to person.)

“If we look at the differences between the first sample and the original [virus from Wuhan, China] that’s missing in the second … that sort of thing proves that they were different, that they parted before they could have entered that person, ”said Richard Tillett, biostatistician at the Nevada Institute of Personalized Medicine and co-author of the Lancet study.

What you should know about reinfection and vaccines

If SARS-CoV-2 doesn’t go away, re-infection may become more likely, even as the virus changes shape to become less fatal or cause less serious illness.

Vaccine developers like Johnson & Johnson
JNJ, -1.67%
and Moderna Inc.
MRNA, + 3.05%
have said they are considering programs to develop COVID-19 boosters or vaccines that will be given regularly in the future.

“For the next few years, we’ll be getting a COVID-19 shot, just like we are getting a flu shot,” said Alex Gorsky, CEO of J&J. said CNBC on February 9th. “We can all imagine a future we can live with, but we can keep the science up to date with the virus.”

According to the CDC, people who have been infected with the virus should continue to be vaccinated as long as they wait at least two months after testing negative.

In the late clinical trials for both approved vaccines, the effects of the vaccines on people previously infected with the virus were largely not studied. But Pfizer Inc.
PFE, -0.35%,
with the German partner BioNTech
BNTX, + 2.70%,
and Modern During the regulatory review, the Food and Drug Administration was separately notified that there was “limited” data to suggest that people who have emerged with the virus are at risk of re-infection and could benefit from vaccination.

“We saw a few case reports here and there of people being re-infected,” said Dr. Tal Zaks, Moderna Chief Medical Officer, in January during an investor call. “But in a context where millions are being infected, I don’t think that’s essential.”

Some health workers at Hackensack Meridian Health, New Jersey’s hospital system, asked administrators if they should get vaccinated if they were already infected. The short answer, according to Dr. Daniel Varga, Hackensack’s chief physician, yes.

“We’re putting these people in the same PSA,” he said, “because they don’t know exactly how long and how effective their acquired immunity is.”

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