Fighting COVID-19: How long does natural immunity against the virus last

New Delhi, Apr 11: With several experts stating that immunity is key to fighting COVID-19, the question is how long does it last.

According to a research by the Institute of Genomics and Integrative Biology (IGIB) says that the immunity last for around 6 to 7 months, but 20 to 30 per cent of those affected lose the immunity after 6 moths.

Dr. Anurag Agarwal, director of IGIB said in a tweet that the key finding of 20-30% of subjects losing virus neutralising activity, despite staying seropositive, at 6 month follow-up helps understand why the large second wave has not spared cities like Mumbai with high seropositivity.

The study by IGIB also established that seropositivity was inversely proportional to the test positivity rate. This meant a higher relevance of antibodies leads to a decline in transmission.

Dr Shantanu Sengupta, senior scientist from IGIB said that in September, when aero-survey was conducted across CSIR laboratories over 10 per cent of the participants were found to have antibodies against the virus.

"Then, we followed up with a fraction of these participants for three and five to six months and conducted a quantitative test to check their antibody levels," Dr Sengupta also said.

"Widespread asymptomatic SARS-CoV2 infections affected nearly 100 million Indians by September 2020 with a subsequent decline in new cases which may be attributable to increased population immunity albeit seeing reduced neutralisation activity at six months this respite may be temporary, the study also noted.

Further it said that at five to six months nearly 20 per cent of the participants had lost the neutralisation activity despite having antibodies. The neutralisation for the rest was also on the decline, it stated.