Health Ministry mulling gathering data on suspected Covid-19 reinfection cases: Source

Taking note of instances of suspected Covid-19 reinfection reported from Telangana, Tamil Nadu, Karnataka, Gujarat, Delhi and Maharashtra, the Union Health Ministry is considering gathering data of such cases to ascertain their veracity, sources said.

They said it needs to be confirmed whether these cases are indeed distinct second infection and not just lingering effects of the first one.

This can be done only by genetic sequence analysis to see if it is the same strain of the virus which had caused the first infection or a different one.

For gathering data on suspected cases of Covid-19 reinfection, the health ministry may also issue guidelines and a format based on which database of all such cases is to be maintained by the State Surveillance Units (SSUs) and District Surveillance Units (DSUs), sources said.

Worldwide, there isn't sufficient evidence on reinfection. Most scientists describe the recurrence as shedding of the residual virus which may happen for up to three months since the first infection is diagnosed, Dr Neeraj Nischal, an associate professor in the Department of Medicine at AIIMS said.

During such a time their RT-PCR test may come positive, he said.

"The second possibility is that it could be a different strain which is causing the infection. To know whether it is reinfection or active infection, one can do viral culture, sub-genomic RNA analysis or compare the genome of the two samples -- that of the first infection and the supposed recurrence.

"But these methods are technically demanding and not easily available," Dr Nischal explained.

ICMR Director-General Dr Balram Bhargava had last week said reinfection of Covid-19 is possible, even though it is a "very rare" occurrence. He, however, stressed that it is not a matter of serious concern.

"We have seen someone gets measles and is supposed to be protected all his life because he generates certain antibodies. But then, we have seen reinfection occurring in measles as well.

"Similarly, we can have Covid-19 reinfection as has been described by the case in Hong Kong. But, it is not a matter of serious concern. It has been noted that whenever reinfection occurs, both the infections have been mild," Bhargava said.

He had earlier said there is a need to find out how long immunity lasts.

Suspected cases of Covid-19 reinfection has also triggered concerns regarding the effectiveness of vaccines being developed.

According to some researches, immunity to coronavirus probably lasts at least three months or even longer, but it has not been scientifically established yet how long immunity lasts.

"Understanding how our immune system responds to the virus is an important step towards vaccine development," Dr Sanjay Rai, a professor in the department of community medicine at AIIMS said.

"What should be of concern is whether the virus is mutating very fast and to find out if the magnitude of mutation is very large. Then the vaccine developed against the virus may not act on this mutant variety. We don't have evidence to suggest drastic mutations in strains of SARS-CoV-2 in India till now," he said.

The concept of immunity after an infection is important because if immunity wears off it could pose a challenge for vaccines, another researcher said, adding that booster shots may be needed.

It is also unclear whether reinfected people would be able to spread the virus. That's another reason why scientists say people should continue to wear masks, practise social distancing and good hygiene, experts said.

Instances of coronavirus reinfection have been reported from Hong Kong, Belgium and the Netherlands raising concerns that herd immunity may not be enough to curb the pandemic.

However, scientists in India and elsewhere said more studies are needed for reliable inference.