How long does the so-called natural immunity to coronavirus disease last?
That’s a question everyone, especially those who contracted Covid-19 and recovered, are asking.
Well, it turns out it takes at least 6-7 months, but between 20% and 30% of those infected lose this immunity after 6 months, according to research from the Institute of Genomics and Integrative Biology (IGIB).
“The key finding of 20-30% of subjects who lost virus neutralizing activity, despite remaining HIV-positive, after 6 months of follow-up, helps to understand why the great second wave of cities like Mumbai did not spare with high HIV,” Dr. Anurag Agarwal, the director of IGIB said in a tweet.
The research is important because it could explain the timing of the second wave of the disease – like the one India is currently witnessing.
It’s also important because it emphasizes the importance of vaccines. Research is ongoing, but most vaccines currently in use are said to protect people from serious infection and death for at least a few years.
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The researchers say the fines could explain why cities like Mumbai and Delhi are witnessing a sharp spike in cases of the viral infection, despite the high levels of HIV – or antibodies. Delhi was found to have an average HIV positivity of just over 56% in January, which, according to doctors in the city, was the reason for the pandemic delay following the November wave.
On Saturday, Delhi registered 7,897 new cases and Mumbai 9,327.
The IGIB study also found that seropositvity was inversely related to the test rate of positivity. This means that a higher prevalence of antibodies leads to a decrease in transmission.
“In September, when we conducted a sero survey in CSIR (Scientific and Industrial Research Council) laboratories, just over 10% of the participants were found to have antibodies to the virus. Then we followed a fraction of these participants for three and five to six months and performed a quantitative test to check their antibody levels, ”said Dr. Shantanu Sengupta, IGIB senior scientist and one of the authors of the accepted study. for publication. in the eLife diary on Saturday.
“After five to six months, nearly 20% of the participants had lost neutralization activity despite having antibodies; the neutralization activity for the rest also declined. Neutralization is the ability of the antibody to kill the virus or completely prevent it from entering a cell.
Of the 10,427 study participants, 1,058 or 10.14% tested positive for antibodies in September last year. The researchers followed 175 of the 1058 for five to six months and found that 31 or 17.7% lost neutralizing activity and had antibodies for an additional eight (4.6%) longer.
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A shorter training of three months 607 out of 1058 showed that only 5.6% lost their neutralizing activity and only 2.8% had no more antibodies.
The study was conducted on the Phenome India cohort consisting of permanent staff, their relatives, students and temporary workers who provide support services in CSIR laboratories in 17 states and union territories.
Widespread asymptomatic SARS-CoV2 infections affected nearly 100 million Indians by September 2020 with a subsequent decline in new cases, possibly due to increased population immunity, although neutralization activity decreased after six months, the study.