As Dr Vipin Vashishtha resumes practice, does he worry about reinfection from the novel coronavirus? “All the time,” he says, without a moment’s hesitation.

Vashishtha has just recovered from Covid-19, following a month of low-grade fever, and is still dealing with the fatigue.

There is always the worry about exposure and reinfection among doctors, says the Delhi-based paediatrician, especially so since children are spreaders. “Some colleagues have changed the way they practise, I have not been able to do so,” he says candidly, since children need to be examined before they are treated.

“Unlike chicken-pox or measles where the immunity is robust, after an individual is infected, it’s not so with SARS-CoV-2”, says Dr Vashishtha, who checks his antibody levels regularly. Reinfection can be discussed academically, but to go through it is an entirely different scenario, he says.

Part of public discussions

“Reinfection” is increasingly getting out of the researchers’ vocabulary and into public discussions. At least three recent studies discussed reinfection, including two from India that looked at its occurrence in healthcare workers.

But in a tragic “first” last week, an 89-year-old Dutch woman died, reportedly from catching the virus a second time.

In fact, a reinfection incident that received much visibility internationally involved a 25-year-old male patient in Nevada, US. In this instance, seen as the first confirmed reinfection in the US, “researchers found evidence that an individual with no known immune disorders or underlying conditions was infected with SARS-CoV-2 in two separate occurrences”, said a note from The Lancet Infectious Diseases journal, where the study was published.

The patient was infected with two distinct SARS-CoV-2 variants within a 48-day time frame, while testing negative in-between infections, the study found. “The patient’s second infection was more severe, resulting in hospitalisation with oxygen support, indicating previous exposure to Covid-19 may not translate to guaranteed total immunity, but that further research into reinfections is required,” the study said.

“There are still many unknowns about SARS-CoV-2 infections and the immune system’s response, but our findings signal that a previous SARS-CoV-2 infection may not necessarily protect against future infection,” said Mark Pandori of the Nevada State Public Health Laboratory, University of Nevada, Reno School of Medicine, and lead author of the study. “We need more research to understand how long immunity may last for people exposed to SARS-CoV-2 and why some of these second infections, while rare, are presenting as more severe,” he said. “So far, we’ve only seen a handful of reinfection cases, but that doesn’t mean there aren’t more, especially as many cases of Covid-19 are asymptomatic. Right now, we can only speculate about the cause of reinfection.”

Reinfection is more the exception than the rule, says Dr Swapneil Parikh, adding that the wider population should be more worried about the primary infection and take precautions against it.

Dr Parikh is co-author, The Coronavirus: What you need to know about the global pandemic and co-author of a recent study of four healthcare workers (HCWs) reinfected by SARS-CoV-2. The study found that “HCWs can get reinfected with SARS-CoV-2 with increased clinical severity in the second episode.”

HCWs are faced with three-fold higher risk than the general community. They are “exposed to patients with varied clinical severity and possibly higher viral loads at different time points,” the study said, calling for greater protection of the healthcare givers.

The research was done in affiliation with Mumbai’s Kasturba Hospital for Infectious Diseases, Delhi’s International Centre for Genetic Engineering and Biotechnology, the Council of Scientific and Industrial Research’s Institute of Genomics and Integrative Biology (CSIR-IGIB), Delhi and Mumbai’s Hinduja Hospital. In another study, IGIB scientists looked at two asymptomatic reinfections in HCWs and found them to be genetically distinct. Their report highlighted the need for genomic surveillance of HCWs, facing a higher risk of primary and secondary infections.


Apart from insights for researchers to further delve into and policy-makers to work with, the key takeaway for the wider population is to not let their guard down and continue taking measures to protect themselves even after an infection, says Parikh.

Pandori further points out, “Overall, there is a lack of comprehensive genomic sequencing of positive Covid-19 cases both in the US and worldwide, as well as a lack of screening and testing, which limits the ability of researchers and public health officials to diagnose, monitor, and obtain genetic tracking for the virus” — an observation that policy-makers could do well to take up.

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