The State government has finally decided to do a sero surveillance study across all districts to ascertain the baseline prevalence of SARS-CoV-2 antibodies in the community, which will give an indication of the proportion of the population which has had prior, silent exposure to the virus.
A press note by the office of Health Minister K.K. Shylaja said a sero prevalence survey would help determine the possibility of yet another wave of COVID-19 and help policy makers evolve appropriate preventive or control strategies.
A sero prevalence study (measuring the SARS-CoV-2 antibody levels in blood samples) will help the State determine the actual extent of the spread of the virus in the community regardless of what the official numbers say because there is still no estimate of the asymptomatic disease transmission.
The sero survey, which is being conducted under the supervision of the Additional Director of Health Services (Public Health) and the nodal officer of the State Prevention of Epidemics and Infectious Diseases Cell, will be coordinated in districts by the respective District Surveillance Officers (DSO).
At least 350 from a district
The study will be conducted in an adult population of 12,100 across districts, with at least 350 samples collected from households in each district. DSOs would choose 10 random healthcare institutions in every district, and 12 healthcare workers from each institution. From five random local self government institutions and five police stations in each district, another 120 samples are being collected .
The State also intends to subject 5,000 blood samples collected from selected blood banks and laboratories in all districts to sero study.
Senior Health officials said that there had been suggestions about collecting blood samples from care home residents too and that many finer details of the sero surveillance study were yet to be finalised.
It has not yet been decided whether the State would opt for IgG Elisa kits or the Chemiluminescent immunoassay (CLIA) for measuring antibody levels. While CLIA is a much more sensitive assay, not all districts have the facilities to perform this test.
Officials said that the Health Department intended to launch the survey next week itself, after finalising the details.
While COVID-19 second wave has led to a major surge in cases across the Western world, in India and in Kerala, the second wave has not been very evident.
An analysis of India’s COVID numbers by a panel formed by the Department of Science and Technology had reported recently that till November, India was missing about 90 infections for every case, while Kerala was missing about 25 infections for every case it detected.
The committee said the country would not see another peak, because of the large number of undetected infections – which meant that even if it was not reflected in the official numbers, infection has spread far in the country, rendering a sizeable population immune.
In November first week, the test positivity rate amongst symptomatic health-care workers in Kerala had been 20%, 10.5% in asymptomatic yet high risk groups, 3.2% in people with no symptoms but who had been tested for COVID prior to surgeries, and 8.3% in people who had reached outpatient clinics in hospitals, according to official data.
