Herd immunity is elusive, rely on disease-induced immunity, says Bhramar Mukherjee -

Herd immunity is elusive, rely on disease-induced immunity, says Bhramar Mukherjee

With nearly 1.7 lakh new cases daily and more than 900 deaths, the second wave of Covid-19 epidemic is galloping in India with no sign of getting abated. Bhramar Mukherjee, a professor of epidemiology and John D Kalbfleisch Collegiate Professor at the School of Public Health, University of Michigan, spoke to Kalyan Ray on the second wave and what future may hold.


How is the second wave of Covid-19 in India different from the first wave? Is it spreading faster?

It is a rapidly rising curve. Last May, the effective ‘R’ (reproduction number– indicates how fast the infection is spreading) was at 1.65 (like we saw on March 21, 2021) but the number of reported daily new cases were around 3,000 then. This March it was around 40,000. So, the rise in the absolute total number of cases looked much more ominous. Initially, it started in two-three states like Maharashtra, Punjab and Chattisgarh. But as you can see, it has quickly spread to all states. Right now, Andhra Pradesh, Uttar Pradesh, Bihar, Jharkhand all have ‘R’ above 2.0.

With India reporting more than 1,50,000 daily news cases, how do you foresee the epidemic will progress in the second surge? Will there be a peak in May as some experts suggest?

The second surges in most countries showed a rapid rise and a sharp fall, unlike the slow and steady climb we saw in the initial wave. These include the UK, South Africa and the USA. It is hard to explain this rapid rise in India, particularly in urban metros that had reported a high degree of sero-positivity at the end of last year, without entertaining the possibility of reinfection and more transmissible new variants. Our models still show a turning of the curve in Maharashtra in early May and India in late May but we have never really predicted the peak reliably in the past. So, I am sceptical of our own model. The bad news is that at the height of the peak, most models are predicting around 3-5 lakh of cases, 20-25,000 hospitalisation and 3-4,000 deaths every day. This will surely overwhelm the healthcare infrastructure.

Uttar Pradesh and Chhattisgarh with poor health infrastructure now report a huge number of cases daily and since ‘R’ values are high in Jharkhand and West Bengal too, those states may also start reporting large numbers. How serious a threat is it?

The virus does not listen to state border patrols. It is coming in most populous states. You can see the ‘R’ is above 2.0 in UP, Chhattisgarh, Delhi, West Bengal, Bihar, Jharkhand and Telangana. We need to restrict interstate travel. We need to throw everything at it right now so that we can avoid a prolonged national lockdown.

The case fatality rate is low as of now–is that a cause of solace and relief?

I think it is a wrong way of looking at things. We all know that reporting of deaths attributed to Covid-19 has been an issue all over the world and calculations based on excess deaths compared with historical trends show that the actual fatality is much higher than what is reported. Even if I believe the reported death data from India, we do care about the total number of deaths and hospitalisations, not just the rates. If you let the disease spread in an unleashed way, you are looking at a huge number of infections even with a low Case Fatality Rate (CFR) like 1.4% The total deaths are a product of infections and fatality rates. And please remember each number is a person.

Many doctors are of the opinion that there’s nothing much to worry about the second wave because even though it generates many cases, the infections are of mild nature and can be managed – do you think such a view is justified?

I care about not just the rate of severe infections and fatalities but the total number. If you let 50% of the country get the infection, you are looking at at least half a million reported deaths. We are at 1,63,000. Are we ready to sacrifice 3,40,000 lives that could be saved?

Also, the need for hospital beds is not measured in terms of rates, it is determined by how many patients show up. More infections would mean more hospitalisations. Another thing that we are forgetting is that each infected person is a petri dish for the virus to mutate. The more you let the virus transmit, the chances are more of seeing new variants.

What went wrong particularly in Maharashtra?

I think the past serosurveys were misleading in implying that we are close to infection-induced herd immunity in certain pockets of Maharashtra. Even our own models cannot explain this spike if we assume 40-50% of people had antibodies and could not get reinfected. Either the serosurveys were highly biased or we indeed have ephemeral disease-induced immunity waning and a certain fraction of the population are getting reinfected. Along with that are new variants circulating which are more transmissible and people are throwing caution to the wind. I always kept saying herd immunity is elusive and instead of relying on disease-induced immunity, India should take advantage of the troughs and valleys of the virus curve and accelerate vaccination. I also believe there is “new fresh prey” for the virus with people who always took serious precautions, now coming out and resuming normal life with less precaution.

Do you foresee a second lockdown? Does such lockdown and night curfews help stem the growth of the epidemic?

I do not envision a national lockdown. Local lockdown and ring vaccination in high transmission areas is what I would foresee. Ring vaccination is where you vaccinate the circle of people with any interaction of any detected case. We should not just vaccinate based on demographics. If we intensify mask mandates and prevent large gatherings, we can avoid some of the more stringent severe extreme measures.

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