How long does so-called natural immunity against coronavirus disease last?
This is a question everyone is asking, especially those who have acquired and recovered Covid-19.
It appears to last at least 6-7 months, but between 20% and 30% of infected people lose this immunity after 6 months, according to research by the Institute of Genomics and Integrative Biology (IGIB).
“The key finding that 20-30% of subjects lose viral neutralization activity despite remaining seropositive helps with the six-month follow-up why the big second wave did not spare cities like Mumbai with high seropositivity,” said 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 what India is currently seeing.
It is also important because it emphasizes the importance of vaccines. Research is underway, but most of the vaccines currently in use are thought to be protected against serious infections and death for at least a few years.
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According to the researchers, the fines may explain why cities like Mumbai and Delhi are seeing a sharp increase in cases of viral infection, despite high seropositivity – or antibodies. Delhi was found to have an average seropositivity of just over 56% in January, which according to city doctors was the reason for the slowdown in the pandemic following the November upturn.
On Saturday, Delhi registered 7,897 new cases, and Mumbai, 9,327.
The IGIB study also determined that seropositivity was inversely proportional to the positivity rate. This means that a higher incidence of antibodies leads to a decrease in transmission.
‘In September, when we conducted a sero-survey in laboratories of the CSIR (Council for Scientific and Industrial Research), it was found that just over 10% of the participants have antibodies against the virus. After that, we followed up a fraction of these participants for three and five to six months and did a quantitative test to check their antibody levels, ‘says dr. Shantanu Sengupta, senior scientist at IGIB and one of the authors of the study accepted for publication. in eLife Journal Saturday.
“At five to six months, almost 20% of the participants lost the neutralizing activity, despite the antibodies; the neutralizing activity for the rest also decreased. Neutralization is the ability of the antibody to kill the virus or prevent it from entering a cell.
Of the 10,427 participants in the study, 1,058 or 10,14% tested positive for antibodies in September last year. The researchers tracked 175 to 1058 for five to six months and found that 31 or 17.7% lost the neutralizing activity, and still had eight (4.6%) longer antibodies.
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A shorter three-month exercise of 608 of the 1058 found that only 5.6% lost their neutralizing activity and that only 2.8% had no more antibodies.
The study was conducted on the Phenome India group which includes permanent staff, their family members, students and temporary staff who provide support services in CSIR laboratories in 17 states and union areas.
“Widespread asymptomatic SARS-CoV2 infections affected nearly 100 million Indians by September 2020, with a subsequent decline in new cases, due to increased population immunity, although the reduced neutralization activity may be temporary at six months,” it reads. the impact statement of the study.