NEW DELHI: Reinfections with SARS-CoV-2, the virus behind Covid-19, is less likely to cause long Covid — a condition that affects at least 65 million people worldwide, according to a study.

Long Covid affects people after an infection caused by the SARS-CoV-2 virus. The condition is not properly defined yet presents more than 200 symptoms. Long Covid risk and severity is known to compromise self-rated health, physical capacity, and cognitive function.

The preprint study, not peer-reviewed yet, showed that the risk of Long Covid was 6 per cent after reinfections from Covid virus compared to 15 per cent after the initial infection.

Fatigue, shortness of breath, neurocognitive symptoms, post-exertional malaise, and smell or taste disturbances were the most reported common symptoms among people with long Covid.

“Severe symptoms were reported 5 to 22 times more often by long Covid cases than by Covid controls, except for fever, cough, insomnia, anxiety, and depression (2.7 to 4.5 times),” said the Laval University in Quebec, Canada.

The study is based on 22,496 online survey participants and 3,978 telephone survey participants.

The results showed that the risk of long Covid was two to three times higher after the initial infection (14.8 per cent). On the other hand, the risk of long Covid was 5.8 per cent after the first reinfection and 5.3 per cent after the second.

Notably, the risk for long Covid was highest following infections with the ancestral strain and lowest after Omicron infections.

However, because Omicron caused such widespread transmission, that strain was associated with the most long-Covid cases.

“The study indicates that long Covid risk is roughly two-thirds lower following reinfection compared to first infection,” the researchers said. “This may be partly related to greater host-specific resistance among individuals who did not have long Covid following their first episode,” they added.