Explained: Can you be reinfected by the novel coronavirus?

Two health workers in Greater Noida are India’s first documented cases of COVID-19 reinfection.
Covid-19 testing sample
Covid-19 testing sample
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Can a person who has had COVID-19 be reinfected? The short answer appears to be yes. In the last nine months or so, the world’s understanding of the SARS-CoV-2 virus that causes COVID-19 has evolved and changed with new scientific research. 

There have been multiple news reports from across the world and India, about persons who've recovered from COVID-19 being reinfected weeks and months later. However, until recently, there has been little research or evidence to prove whether it’s a case of reinfection.

Most of these accounts of reinfection were based on RT-PCR (Real-time Polymerase chain reaction test) positive results. Scientists have pointed out that the risk of false positives is high with the test kits detecting old particles of the virus, which may no longer be infectious.     

World’s first case

The world’s first documented case of reinfection was reported in Hong Kong in August. Unlike multiple other cases in the past, this was the first known instance where genome sequencing was carried out to establish reinfection. A 33-year-old man who had recovered from COVID-19 in April, tested positive for the SARS-CoV-2 virus four-and-a-half months later. Researchers from the University of Hong Kong said that the man, who had travelled from Spain to Hong Kong, had contracted a different ‘variant’ of the virus. The man, who had mild symptoms the first time, did not present with any symptoms when he tested positive in August, with his infection having been detected during a screening at the Hong Kong airport. 

The Indian cases

In India, two health workers, who were both asymptomatic, are reported to be the first documented cases of reinfection. Researchers from the CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), who carried out the genome sequencing, said that the reinfection in the two asymptomatic health workers were ‘unique’, as in other instances patients were symptomatic at least once.   

According to the pre-print research paper, which is yet to be peer reviewed, the 25-year-old man and a 28-year-old woman, who were posted in the COVID-19 unit of the Government Institute of Medical Sciences in Greater Noida, first tested positive in May. The two were asymptomatic and were subsequently discharged based on a negative RT-PCR test and resumed their duties at the hospital. 

The two health workers, however, ended up testing positive over three months later. “Both individuals were asymptomatic but had a higher viral load in the second episode of reinfection,” stated the paper.  

Based on the sequencing and genome analysis carried out on the nasal/oral swabs in both episodes, the researchers conclude that it is a case of reinfection with the two patients being reinfected by genetically distinct variants.   

“Our analysis demonstrates that asymptomatic reinfection could potentially be an under-reported entity with implications in long term surveillance of SARSCoV-2 infections,” stated the researchers. 

They also added that as both individuals had a higher viral load in the second episode, it highlights the need for continuous surveillance in healthcare systems. 

So what is the risk of reinfection?

Indian Council of Medical Research (ICMR) Director General Balram Bhargava on Tuesday said the chances of reinfection were “very, very rare”. Downplaying fears over reinfection, the ICMR Director said,  “We have seen that someone gets measles and he is supposed to be protected all his life because he generates certain antibodies, but then we have seen reinfection occurring in measles. Similarly, we can have reinfection with COVID-19 as has been described by the case in Hong Kong and it is not a matter of serious concern.”

Speaking to TNM, Dr Shahid Jameel, a virologist and the Director of the Trivedi School of Biosciences at Ashoka University, points out that reinfection isn’t necessarily bad news. “When you get infected the second time around, there is simply infection and not disease. We really should not be worrying about this,” he explains, “Infection simply means that you get exposed to the virus, you get infected but then the immune system from a previous infection, from memory, is able to recognise that you have the same virus infecting the body and it mobilises itself very quickly and controls the infection. So it doesn’t let you become sick.”   

He adds that in many acutely infecting viruses, reinfection is not unusual. “So there is nothing unusual here. People are so anxious with the virus, that any little thing is considered to be too good or too bad and this falls in that category,” says Dr Jameel.   

What do the findings say about our immunity to COVID-19? 

Scientists are yet to determine how long immunity to COVID-19 can last. Some research has suggested that the antibodies produced after a person has been exposed have dropped within two months of being infected by the novel coronavirus. However, this is no reason to panic. 

There are two types of immunity. One which fights off the infection almost immediately is called innate immunity. The second is adaptive immunity. The World Health Organisation (WHO) explains, “This non-specific (innate) response is followed by an adaptive response where the body makes antibodies that specifically bind to the virus. These antibodies are proteins called immunoglobulins. The body also makes T-cells that recognise and eliminate other cells infected with the virus. This is called cellular immunity. This combined adaptive response may clear the virus from the body, and if the response is strong enough, may prevent progression to severe illness or reinfection by the same virus.” 

Dr Jameel further explains the immune response, offering an example of a person being reinfected by SARS-CoV-2 after a year. “After a year, the person's antibodies would have waned off. S/he would not have as good quality antibodies anymore to neutralise the virus coming in, so there will be limited infection. But from the previous infection, the body will have memory. And it mobilises this memory very quickly to produce more antibodies, and to produce more T-cells that can neutralise the virus and kill viral reservoirs,” says Dr Jameel.

What does this mean for vaccine research? 

Many scientists, including Dr Jameel, agree that reinfection will not change research to produce a vaccine. “Most successful vaccines only prevent disease, they don’t prevent infection. And so will be the case with the COVID vaccine. If the natural infection doesn’t give you long-lasting immunity, a vaccine isn’t going to give you long-lasting immunity. This is becoming very clear from COVID, we won’t get long-lasting immunity.” 

And while there are variants of the SARS-CoV-2 virus that are causing reinfection in some cases, its mutation isn’t a cause for concern yet.  

“Every virus mutates but it’s the rate at which the mutation happens [which should also be considered]. Thankfully, coronaviruses are the slowest mutating RNA virus known to us. They are roughly 1,000 times slower than the flu virus. Yes, they are mutating, but so far we have not seen the kind of mutations that would impact the vaccine,” says Dr Jameel. 

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