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COVID reinfection is rare — but not everyone has the same risk, study finds

·3 min read

Although COVID-19 reinfection is rare, the risks are higher for some than others.

A review of more than 9,000 electronic medical records of people who had severe COVID-19 in the U.S. found that less than 1% (63 people) contracted the disease again within an average of 3.5 months after first testing positive. The finding suggests a serious first round of the illness may protect you from a second terrible one.

Of those in the study who were reinfected, two died. The high survival rate for reinfection could be attributed to more effective medical treatments compared to those earlier in the pandemic, according to the paper recently published in the journal Clinical Infectious Diseases.

Data collected between December 2019 and November 2020 from 62 health care facilities showed there were lower rates of respiratory and liver failure among the reinfected patients; none of the people needed mechanical ventilation their second time around either.

But people with asthma or a nicotine dependence faced a nearly two and three times higher risk of COVID-19 reinfection, respectively. What’s more, nonwhite patients, particularly Black and Hispanic people, were about two times more likely to be reinfected.

Meanwhile, there were “no significant differences based on age or sex among patients with and without reinfection,” the researchers noted.

The team said their findings “strongly suggest” the need to continue following infection prevention measures even after getting sick once because it’s still unclear how long immunity lasts — a job easier to accomplish with COVID-19 vaccines.

“This is one of the largest studies of its kind in the U.S., and the important message here is that COVID-19 reinfection after an initial case is possible, and the duration of immunity that an initial infection provides is not completely clear,” study lead researcher Dr. Adnan Qureshi, a professor of clinical neurology at the University of Missouri School of Medicine, said in a statement posted Tuesday.

Past research has shown that both cigarette smokers and people with asthma face higher risks for respiratory viral infections, which could explain why people with those conditions are more likely to get reinfected with the coronavirus, which attacks the respiratory system.

It’s unclear if COVID-19 reinfection is generally more or less severe

What remains unclear is whether reinfection with COVID-19 is generally more or less severe than primary infection.

Some studies show patients who contracted the virus twice have antibodies that may help prevent serious illness the second time around, but other research has shown those special proteins diminish over time — sometimes within the first three months after infection.

There are other parts of the immune system such as T cells and memory B cells that can provide immunity and thus protect someone from severe disease during reinfection even without antibodies, but more research is needed to confirm the theory, the team said.

What’s becoming more clear is that “the quality, quantity and durability of protective immunity” from the COVID-19 vaccines appears to be better and higher than that of natural infection, research shows; scientists are still learning how long protection for both lasts.

The study did not test whether coronavirus variants played a role in reinfection rates, however emerging evidence shows some of them are more contagious and can lead to more serious illness.

The Centers for Disease Control and Prevention recently joined the World Health Organization in adding the Delta variant, which was first discovered in India, to its list of “variants of concern.”

Top health officials say the variant could soon become the most dominant version of the coronavirus spreading in the U.S.; it currently accounts for about 10% of infections.

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