How long does the so-called natural immunity against coronavirus disease last?
This is a question that everyone is asking, especially those who have contracted Covid-19 and have recovered.
It seems to last at least 6-7 months, but between 20% and 30% of those infected lose this immunity after 6 months, according to research conducted by the Institute of Genomics and Integrative Biology (IGIB).
“The key finding of 20-30% of subjects who lost their virus neutralization activity, despite remaining HIV-positive, at 6 months of follow-up helps to understand why the second big wave did not spare cities like Mumbai with high seropositivity “Said Dr. Anurag Agarwal, the director told IGIB in a tweet.
The research is important because it could explain the timing of the second wave of the disease – such as the one India is witnessing at the moment.
It is also important because it emphasizes the importance of vaccines. Research is ongoing, but it is believed that most vaccines currently used protect people from severe infections and death for at least a few years.
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The researchers say the fine could explain why cities like Mumbai and Delhi are witnessing a sharp rise in cases of viral infection, despite having high seropositivity – or antibodies. Delhi turned out to have an average HIV level of just over 56% in January, which doctors in the city believe was the reason for the slowdown in the pandemic after the November rise.
On Saturday, Delhi registered 7,897 new cases and Mumbai 9,327.
The IGIB study also found that seropositivity was inversely proportional to the positivity test rate. This means that a higher prevalence of antibodies leads to decreased transmission.
“In September, when we conducted a sero-survey in the laboratories of CSIR (Council for Scientific and Industrial Research), just over 10% of participants were found to have antibodies against the virus. Then, we followed up with a fraction of these participants for three to five to six months and performed a quantitative test to check their antibody levels, ”said Dr. Shantanu Sengupta, a senior IGIB scientist and one of the authors of the study accepted for publication in the eLife journal on Saturday.
“At five to six months, almost 20% of participants lost their neutralizing activity despite antibodies; neutralization activity for the rest was also declining. “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 1058 for five to six months and found that 31 or 17.7% lost their neutralizing activity and another eight (4.6%) had antibodies.
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An exercise shorter than three months of follow-up 607 of 1058 found that only 5.6% lost their neutralizing activity and only 2.8% no longer had antibodies.
The study was conducted on the Phenome India cohort, which includes permanent staff, their family members, students and temporary staff providing support services in CSIR laboratories in 17 states and territories of the union.
“Asymptomatic infections spread by SARS-CoV2 affected almost 100 million Indians by September 2020, with a further decrease in new cases, which can be attributed to increased immunity of the population, although it saw a neutralization activity reduced to six months, this respite may be temporary, ”reads the study’s impact statement.