Reinfection from Covid-19 is rare, severe disease is even rarer, a study of people in Qatar finds

The study, published Wednesday in the New England Journal of Medicine, found that there were few confirmed infections among 353,326 people who contracted Covid-19 in Qatar, and re-infections were rare and generally mild.

The first wave of infections hit Qatar between March and June of 2020. In the end, about 40% of the population had detectable antibodies against COVID-19. Then the country experienced two more waves from January to May of 2021. This was before the most contagious delta variant.

To determine how many people got infected again, scientists from Weill Cornell Medical College in Qatar compared records of people with confirmed PCR infections between February 2020 and April 2021. They excluded 87,547 people who got vaccinated.

The researchers found that of the remaining cases, 1,304 were infections. The median time between first illness and reinfection was about 9 months.

Of those who re-infected, only four were severe enough that they had to go to hospital. There have been no cases where people have been sick enough that they need treatment in the intensive care unit. Of the initial cases, 28 were considered critical. There were no deaths among the re-infected group, while there were seven deaths in the primary infections.

“When you only have 1,300 infections among that many people, and four cases of severe illness, that’s pretty cool,” said John Alcorn, an expert in immunology and professor of pediatrics at the University of Pittsburgh, who was not involved in this study.

Study has limits. This was done in Qatar, so it is not clear if the virus will behave in the same way elsewhere. The work was done when alpha and beta variants were the cause of many re-infections. There were 621 unidentified and 213 cases of ‘wild-type’ virus. There was no mention of the delta variant, which is now the dominant strain. This could have an impact on the number of reinfections.

Previous studies have shown that natural immunity reduces the risk of infection. One study in Denmark and published in March found that most people who became infected with Covid-19 were protected from reinfection that remained stable for more than six months, but checking the demographics of those who were infected again showed that most of them were people 65 and older. Age. This study does not say how long the protection will last, nor does the new Qatar study.

Alcorn’s own research on natural immunity shows that antibody levels also vary widely from person to person. Scientists still don’t know what the level of protective antibodies is, but in some cases, levels after infection may not be enough to prevent someone getting sick again.

“It must be determined whether this protection from severe illness when infected again lasts longer, similar to the immunity that develops against other seasonal coronaviruses ‘colds’, which generate short-term immunity against recurrence of mild infection but long-term immunity against disease. Most severe with reinfection,” the study said. “If this is the case with SARS-CoV-2, the virus (or at least the variants studied so far) could adopt a milder pattern of infection when it becomes endemic.”

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Dr Kami Kim, an infectious disease specialist who is not affiliated with this study, said people need to be careful not to get the false impression that this means people do not need to be vaccinated if they contract the Covid virus. -19.

“It’s like asking do you need airbags and seat belts?” said Kim, director of the University of South Florida’s Division of Infectious Diseases and International Medicine. “Just because you have airbags doesn’t mean seat belts won’t help you and vice versa. It’s good to have protection for both.”

It’s not worth the risk with the disease, Kim said, especially because the infection can bring long-term effects with it. “The risk of infection with Long-Covid virus is much higher than the risk of getting a vaccine,” Kim said.

Vaccinations not only protect the individual from contracting the disease, but also protect the community.

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“Modern medicine is so much better, and people get cancer and live with autoimmune diseases and thrive. Unless you’re very close, you don’t always know who is most at risk of getting a more serious disease, and you can literally put the people you care about at risk if they get sick and expose them,” Kim said. “Without vaccination, you cannot return to a normal life.”

Reducing the number of diseases also limits the possibility of developing more variants, variants that can be more dangerous than what is currently common.

There is another important lesson from this study, Alcorn said.

“Vaccines are still the best way we have to get to the same place where these people were infected, for sure,” Alcorn said. “The main finding from this study here is that there is hope that through vaccination and through recovery from infection, we will get to the level where everyone has a certain level of protection.”

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