Omicron reinfection: How likely is it? Experts weigh in

Several people in South Africa, the epicenter of the new wave, have been infected with the omicron variant of SARS-CoV-2 after recovering from the disease caused by the virus, anecdotal evidence showed. 

Health experts are divided over if this is a characteristic of the fifth variant of concern. It is certainly possible, said Stanley Weiss, a professor at the Rutgers New Jersey Medical School and department of Epidemiology at the Rutgers School of Public Health. “Omicron is highly contagious and it would appear to not induce fantastic protective immunity.”

Dr Thomas Russo, professor and chief of infectious disease at the University at Buffalo in New York, told the media “if you had a mild infection, didn’t get a very good immune response, and you get exposed again with a big dose of the virus, it’s definitely possible.”

Omicron reinfection is possible in immunocompromised persons as well, said Dr Eric Feigl-Ding, epidemiologist, health economist and a senior fellow at the Federation of American Scientists. The expert concurred that a reinfection after a recent omicron infection is entirely possible. 

An omicron wave is ripping through India, with nearly 10,000 cases across the country and a daily positivity rate of 16.41 per cent. The appalling tally was logged in a month’s time. Experts, however, are yet to see repeat omicron infections in the country. 

Shahid Jameel, eminent virologist and former head of the Indian SARS-CoV-2 Genomics Consortium (INSACOG), told Down To Earth:

This is a little unusual. Omicron really hasn’t been around for that long. Once someone is infected, they raise an immune response against it. Someone getting reinfected so quickly is a low possibility but possible still in someone who has a very weak immune system.

Quick reinfection would have been observed with delta and other previous variants as well if the omicron reinfection is possible, he added. 

Antibodies do wane over time but not so quickly, he said, stressing that omicron has been in India for a very short time, he said. “I would not go by anecdotal evidence so early on.

The varying sensitivity of RT-PCR (Reverse transcription polymerase chain reaction) tests can be a reason behind the “omicron reinfections”, according to Giridhar R Babu, head of Public Health Foundation of India. 

“If someone has been infected with omicron, has recovered and tested negative but tests positive soon after, it may not necessarily mean they’ve been infected twice,” he said. A more sensitive test might still pick up the virus, the expert added. 

One prolonged episode of infection is more likely than two incidental episodes of omicron infection, according to Babu. “Recovery time with an omicron infection is fast but symptoms like sore throat and fatigue may linger for a long time.”

The observation that omicron is faster to come and go is true only for now, he explained. “We still need to understand the impact this variant has on long COVID-19 cases,” he said, adding that he is yet to see any real data from South Africa, the United Kingdom, the United States and even India.

Past infections from preceding variants hardly provide any protection against omicron, studies have confirmed. A previous infection provided 85 per cent protection against a reinfection for around six months, a report from the Imperial College London COVID-19 response team found. Protection against reinfection has fallen to 19 per cent against an Omicron infection, the study showed. 

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