Indian Council of Medical Research Director General Balram Bhargava on Tuesday said that there were at least three suspected cases of coronavirus reinfection in the country, The Indian Express reported. Two such cases were in Mumbai and one was in Ahmedabad.

Bhargava added that India was considering 100 days as the cut-off period for reinfection. The World Health Organization had itself not yet spelt out the terms of reinfection, and whether it was 90 days or 100 days or 110 days, he said, adding that India had so decided to set the period at 100 days.

“We have got some data from the WHO, which says that there are about two dozen reinfection cases in the world at the moment,” he said, according to PTI. “We are looking at the ICMR database and finding out those who have had reinfection and making telephonic contact to get some data out of them.”

The director general added that the mutations that were likely to have caused the reinfections would have little impact on the Covid-19 vaccine clinical trials.

On Sunday, Union Health Minister Harsh Vardhan had said that an ICMR analysis revealed that many cases reported as reinfection of Covid-19 were misclassified as the RT-PCR tests detected dead virus shed for prolonged periods since recovery. “Actual reinfection would mean a fully-recovered person getting infected by a freshly-introduced virus in his/her body, belonging to the same or different strain,” he had said, adding that the ICMR was commissioning a study to understand more about reinfection cases.

In September, a 27-year-old woman in Bengaluru was reported to be reinfected with the coronavirus, a month after her first bout. The woman had mild symptoms of Covid-19. On August 26, Telangana Health Minister Eatala Rajender had said that two cases of coronavirus reinfection were reported in the state.

The world’s first confirmed case of reinfection was reported by scientists in Hong Kong on August 24, reportedly backed up by genetic sequences of the two episodes of the 33-year-old man’s infections in March and in August. Bhargava had at that time said there was “no need to be alarmed immensely” over the reinfection case but had also admitted that it was not known how long immunity lasts in Covid-19 patients.

India’s coronavirus tally rose to 72,39,389 on Wednesday as the country reported 63,509 new infections in 24 hours. The toll climbed by 730 to 1,10,586. India’s active cases stood at 8,26,876, while the number of recoveries rose to 63,01,927. The country’s recovery rate is 86.78% and the mortality rate stood at 1.53%.