Anup Malani on Interpreting Sero-surveys and Understanding Herd Immunity

Herd Immunity A Moving Target As People Start To Mingle More

Chennai: Anup Malani, professor at the University of Chicago Law School and the university's Pritzker School of Medicine, is a visiting senior fellow at IDFC Institute, an economic development-focused think-tank in Mumbai. Malani conducts research in law and economics, development economics and health economics, and has been leading a series of COVID-19 sero-surveys in cities and states across India with IDFC.

Based on seroprevalence data, IDFC has advised state governments on policy to control the spread of the disease, and now on vaccine allocations. He spoke to Rukmini S. about innovations in collecting COVID-19 data in India, the limits of sero-surveys, and how herd immunity thresholds for the disease can change.

Edited excerpts:

It became evident quite early that sero-surveys were going to be very important in understanding the COVID-19 pandemic. How was IDFC able to pull off multiple sero-surveys across the country? What were the logistics of that like?

The first thing I want to say is India is actually remarkable. If you were to list countries by the number of COVID-19 sero-surveys or population-level surveys that they did, India would be close to the top of that list. If you adjust that list by income and healthcare capacity, I think India probably outperformed most governments, other than some in East Asia perhaps. A lot of different organisations have done many sero-surveys in India. And it doesn't stop there. There are also prevalence surveys, a lot of scientific research, surveys of what's happening to incomes. It's remarkable. After we finish blaming a bunch of people, we should just say there are ways in which India was quite successful.

Importantly, IDFC realised the need to work with governments, to adapt to the circumstances, and that speed was key. We immediately identified state governments that were willing to allow or undertake COVID-19 sero-surveys for their particular public policy needs. If there were specific questions that government officials had, the sero-survey would be tailored around that. IDFC worked to get funding for these through non-profits or NGOs in India, or sometimes directly from the government, because we had to come together to assemble a sort of private task force to help the government respond once the lockdown was declared.

For example, in Mumbai, we were able to work directly with the municipal corporation to get approvals and support. We worked with the public Kasturba Gandhi Hospital and Tata Institute of Fundamental Research to get together the scientists needed to implement the sero-survey, and worked on the survey design with them, because we knew that slums were going to be particularly at-risk. In Pune, [the local administration] did the sero-survey independently, and very quickly. We've also been working with the Andhra Pradesh government, but even before that, they did a rural and urban sero-survey of four districts. Around that time, Bihar was also doing random testing of returning migrants; not antibody tests but RT-PCR. Then in Karnataka, [former health commissioner] Pankaj Pandey and others in the health ministry were open to doing a statewide COVID-19 survey that would really give us a sense of what was going on in rural areas. IDFC also collaborated with the Centre for Monitoring Indian Economy (CMIE), which provided the Karnataka sample, and a number of local laboratories. Once we had those two successes [in Karnataka and Mumbai], we got more requests from state governments, as in Tamil Nadu and the repeat survey in Mumbai.

IDFC plugged all these pieces of information together, correlating official data with seroprevalence, to be able to advise states on how to go about suppressing the spread of COVID-19. Now, we're advising on vaccine allocations, again using the seroprevalence route. We're not just gathering data, but trying to guide policy based on that data.

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