Sero survey: Antibodies are not present in all those who recovered from COVID-19! In the sero survey conducted by the National Centre for Disease Control (NCDC), it was found that as many as 97 out of 208 patients who had earlier tested positive for the infection, did not have antibodies, according to a report in IE. The organisation says this finding indicates towards the possibly “transient” nature of the immune response that is generated by the virus. An arm of the Union Ministry of Health and Family Welfare (MoHFW), the NCDC’s sero survey report stated that the immune response that is generated in Delhi’s population could be short-lived due to the large number of floating populations from Ghaziabad, Noida and Gurugram.
The IE report stated that NCDC further called for sero-surveys in all the major cities and towns in the NCR where such surveys have not yet been conducted. The NCDC had prepared the sero-survey report on July 21 and has been submitted to the Delhi High Court. The submission is in relation to an ongoing hearing regarding the testing in Delhi. According to the IE report, the Delhi government had also sought the report from the NCDC in a letter on August 27, and Delhi Director General of Health Services Nutan Mundeja informed the court that it also received the report on Monday during the hearing.
The report stated that the July survey found a sero-positivity rate, or the rate of presence of antibodies, of 22.83% among the 21,387 people that were tested. Of the surveyed people, 208 people had said that they had previously tested positive for coronavirus using the RT-PCR test. The IE report quoted NCDC survey as stating that of these 208, only 53.37% or 111 participants were found to be seropositive, or having antibodies, while 97 were seronegative. These findings, the NCDC survey stated, corroborated the with the presently available scientific knowledge that the immune response to the novel coronavirus could be transient in nature.
The second round of serological survey was carried out in Delhi by the Maulana Azad Medical College in August. This survey, the IE report stated, covered as many as 15,000 people, out of whom 29% people were found to be seropositive. This, the Delhi government had said, translated to about 60 lakh of the city’s 2-crore population having antibodies.
However, the report quoted NCDC’s survey report as saying that everyone should be careful in trying to relate the seroprevalence with the natural immunity that is acquired after the infection. This caution, the NCDC said, should be taken because of the “meagre” scientific evidence that is available regarding the immune response triggered by the virus. NCDC further stated that there was no conclusive evidence on how long the sero-positivity would last and the level of protection that seroprevalence of antibodies would render.
It further stated that since Delhi had a large floating population, any immune response substantially generated among the population would continue to be short-lived. This would lead to a constant chance of increase in cases and fatalities.