Statewide sero survey will help govt. strategise better, say experts

Extent of virus spread and the level of natural immunity likely to be developed can be ascertained

As community transmission of SARS-CoV-2 seems to be fairly established in the State, the time might just be right for Kerala to undertake a sero surveillance study across districts. This will help the State assess the course of the epidemic, plan its testing strategy among specific populations, and adopt suitable public health interventions.

It also helps that there are better antibody testing kits (ELISA IgG kits) and modalities (CLIA immuno assay) validated by the Indian Council Medical Research, available in the market now, than during the initial months of the pandemic.

“A population-based sero surveillance study will help the State pick up silent or asymptomatic cases. Our current information on the epidemic is based solely on the data we have derived from the test results. But a serial sero epidemiology study can help us track the epidemic, monitor the trend of infection in specific populations and geographic locations and any socio-demographic factors influencing the epidemic,” says Rakhal Gaitonde, Professor, Achutha Menon Centre for Health Science Studies.

In fact, the expert committee headed by B. Ekbal has now recommended that the State does a sero surveillance study like the one done in Delhi and Dhaaravi in Mumbai so that the extent of the spread of the virus in the community as well as the proportion of the population which might have been rendered some level of natural immunity against the disease can be ascertained.

‘Make earlier study public’

The committee has also suggested that the State come clean on the sero surveillance study it had done in the second week of June, the details of which were never shared in the public domain. It has pointed out the importance of analysing and interpreting the data from that study properly.

The data never saw the light of the day and the Health Department blamed the “poor” quality of the rapid antibody kits for the “unexpected results” and high levels of sero prevalence — reportedly between 3% and 19% — found in districts .

No perfect test

“Burying that data blaming the quality of the rapid test kits was a huge mistake because a proper statistical assessment of that data could have given us an early warning about the clusters that broke out in different parts of the State soon after. In the midst of the pandemic, there could be no perfect test. Even the PCR test, given its sensitivity, is expected to miss about 30% of the infections and yet we consider it as the gold standard for COVID-19 testing,” a senior public health expert pointed out.

“Kerala should have no hesitation about doing this [sero survey] because at this stage of the epidemic, if would set our minds at rest if we can assess what proportion of the State’s population has already been exposed. It will give us an idea how soon the current public health crisis will blow over,” he added.

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