The risk of mortality, hospitalisation, and serious health problems from COVID-19 increases dramatically with reinfection, independent of vaccination status, according to a study released on Thursday


“Reinfection with COVID-19 increases the risk of both acute outcomes and long COVID,” according to Dr Ziyad Al-Aly of Washington University School of Medicine in St Louis. “This was evident in unvaccinated, vaccinated, and boosted people.”

The findings were derived from data obtained by the US Department of Veterans Affairs on 443,588 patients with one SARS-CoV-2 infection, 40,947 with two or more illnesses, and 5.3 million noninfected individuals from March to April . The majority of the study participants were men.

Reinfected patients had a more than doubled risk of death and a more than tripled chance of hospitalisation compared to those who were only infected with COVID-19 once. According to a paper published in Nature Medicine, they also had an increased chance of problems with the lungs, heart, blood, kidneys, diabetes, mental health, bones and muscles, and neurological disorders.

“Even if one had prior infection and was vaccinated – meaning they had double immunity from prior infection plus vaccines – they are still susceptible to adverse outcomes upon reinfection,” Al-Aly, the study’s leader, explained.

Repeat infections were found to be more than three times more likely to cause lung difficulties, three times more likely to cause cardiac problems, and 60% more likely to cause neurological disorders than people who had only been infected once. The increased risks were most noticeable in the first month after reinfection, although they were still present six months later.

According to the researchers, the cumulative risks and burdens of repeat infection increased with the number of infections, even after accounting for differences in COVID-19 variants such as Delta, Omicron, and BA.5.

“We had started seeing a lot of patients coming to the clinic with an air of invincibility,” Al-Aly told Reuters. “‘Does getting a reinfection really matter?’ they wondered.” Yes, it most emphatically does.”

He said that “people should be aware that reinfection is consequential and should take precautions” as the Christmas season approaches, with travel and indoor gatherings.

“We’re not advocating draconian measures, but maybe wear a mask if you’re flying,” Al-Aly added. “If you’re in a supermarket, keep in mind that the person next to you may have a weakened immune system, and wearing a mask may help to protect them.”

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