Researchers’ analysis of Qatar’s COVID-19 pandemic data shows that reinfected patients fared better than those contracting coronavirus for the first time.
The prestigious New England Journal of Medicine published a letter on Wednesday from Qatari medical researchers announcing their findings, which are not peer-reviewed.
Laith J. Abu-Raddad is the first signatory of the letter describing Qatari research comparing reinfected patient responses with newly infected patients.
Qatar’s first wave of SARS-CoV-2 infections occurred between March and June 2020, after which approximately 40% of the population had detectable antibodies against COVID-19, according to Abu-Raddad. The country later experienced two back-to-back waves from January to May 2021, triggered by new variants, which created an opportunity to study reinfections.
The researchers studied the nation’s databases of all coronavirus–related data since the onset of the pandemic. “We investigated the risk of severe disease (leading to acute care hospitalization), critical disease (leading to hospitalization in an intensive care unit) and fatal disease caused by reinfections as compared with primary infections,” said Abu-Raddad.
He explained they studied 353,326 persons confirmed with polymerase-chain-reaction (PCR) infection between February 28, 2020, and April 28, 2021, after excluding 87,547 vaccinated people. The study defined primary infection as the first PCR-positive swab and reinfection represented the first PCR-positive swab obtained at least 90 days after a patient’s primary infection.
Abu-Raddad noted no cases of critical disease at reinfection while there were 28 cases at primary infection. Nobody who was reinfected died from COVID-19 but seven patients with primary infections died, according to study results.
“Reinfections had 90 percent lower odds of resulting in hospitalization or death than primary infections,” wrote Abu-Raddad. “Four reinfections were severe enough to lead to acute care hospitalization. None led to hospitalization in an ICU, and none ended in death.”
The researchers reported reinfections were rare and generally mild, perhaps because of a primed immune system after primary infection.
“Accordingly, for a person who has already had a primary infection, the risk of having a severe reinfection is only approximately 1 percent of the risk of a previously uninfected person having a severe primary infection,” noted Abu-Raddad.
The published letter included a statement that more than one-third of the patients were infected with earlier variants of COVID-19, so the results may not stand up when exposed to delta or omicron variants. Still, the results appear to be good news for people who have previously contracted the virus.
“When you have only 1,300 reinfections among that many people, and four cases of severe disease, that’s pretty remarkable,” John Alcorn, an immunology expert who teaches at the University of Pittsburgh, told CNN reporter Jen Christensen. Professor Alcorn was not affiliated with the published study.
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