India likely to reach herd immunity against COVID-19 by August: Senior virologist

John argued even with 1% mortality rate, India should anticipate few million deaths

kolkata swab test salil bera A lab technician preparing for a swab test in Kolkata | Salil Bera

Dr T. Jacob John, one of India's top virologists, is former head of the Indian Council for Medical Research's Centre for Advanced Research in Virology. John is also retired professor and head, departments of clinical virology and microbiology at CMC, Vellore. In view of the rising cases of coronavirus in India, John says that trend will continue. He argued the focus should be on healthcare management at the district level, and that wearing of masks and personal hygiene measures should be strictly enforced.

Excerpts from an interview with Dr John:

The director of AIIMS, Dr Randeep Guleria, has said that India would reach its peak in the number of cases next month. What is your assessment of the spread of infection?

My own simple calculation tells me that sufficient herd immunity will be reached by end of first week of August, when the epidemic curve should show downward trend. My calculation is based on estimate of total infected people by mid-April as 2 lakh. Forward calculation shows that the required herd immunity level is likely to be achieved by early August. But, mind you there are estimates and assumptions involved—therefore, there could be an unknown margin of error. However, for planning the management of the epidemic, we need projections and mine is very close to that of the AIIMS director—mine is 5-6 weeks later. We both must be using different methods of calculation. Had there been no lockdown and no masks, peak might have been in May-June period. Still, if we don’t count the numbers properly, we won’t have an accurate estimate. Deaths in real time will be grossly unknown and underreported, and in 2020-2021, we should notice the missing millions.

Government officials say we are testing significantly higher numbers, and a section among them has attributed rising numbers to a higher level of testing. How do we understand this trend?

Testing does not infect people and testing cannot be cause of increasing numbers. We in India will have high infection burden because of huge population size. But our mortality rate should be relatively low because we are a young demography; 26 million annual (birth) cohort implies we have more children than senior citizens.

Deaths due to COVID-19 are higher in senior citizens and in those with chronic non-communicable diseases. So, had the government planned well, we could have coped reasonably well. But it looks like the government did not expect such an increase in numbers. From the beginning, the government was exhibiting overconfidence that we will overcome the epidemic. Even with low mortality rate—say of 1 per cent—we should anticipate a few million deaths, spread over 4-5 months.

If the increase continues, what sort of health challenges do we see in the coming months? How can we overcome them?

COVID-19-related healthcare needs are over and above usual healthcare needs. Do we have such surge capacity? The government had time from February first week to plan until April-May. District hospitals must remain for non-COVID healthcare needs and hospital beds should be pooled from public and private sectors for COVID-19 during May through September. All expenses should be borne by the government.

We also need a case definition of COVID-19 instead of clubbing it with influenza. Dr M.S. Seshadri and I have published the diagnostic criteria in Christian Journal of Global Health, April issue, and submitted it to the Tamil Nadu and Kerala governments. These criteria must be taught to all healthcare professionals, and COVID-19 symptomatic people must be clinically diagnosed and home-managed with quarantine, under telephone supervision by assigned doctors. If and when COVID-19 becomes severe with breathing difficulty and low blood oxygen level, they should be admitted in COVID beds.

When they are severely ill and need mechanical ventilation, then they should be given COVID-19 convalescent plasma. That should be standard therapy. When remdesivir becomes available, that too.

Such healthcare organisation and pooling public-private sectors must be an intra-district exercise. Similar exercise should be done in cities.

How can a sudden surge be prevented?

We have to face the reality [of rising cases]. Had we strictly enforced 100 per cent use of face masks when out of home, the increase would have been slower. We know that the lockdown could not have been 100 per cent effective for cultural and behavioural (poor sense of discipline) reasons. It has been very leaky in the best of communities.

Now, we know we have not been able to restrain the speed of spread. We can prevent a sudden surge if we can ensure 100 per cent compliance of measures such as wearing a mask, together with the practice of hand hygiene using sanitiser and soap.

Even then, all those who have been infected till now will show up in the next two weeks or more.

All old people—65 and above—and all with co-morbidities must be under reverse quarantine to prevent exposure to the virus.

What about other infectious diseases that will also start to affect the country in the coming months?

All non-COVID disease epidemiology would have been affected by the lockdown and I hope the ICMR is observing the changes. It would be interesting to know whether all respiratory-transmitted infectious diseases would have reduced, such as influenza and childhood acute respiratory illnesses. All immunisation would have reduced but most childhood vaccine-preventable ones are likely to be markedly reduced due to lockdown and use of face masks.

One particular worry is polio. Until January, we were giving bivalent OPV with types 1 and 3 vaccine viruses. Stopping suddenly is likely to put the country at high risk of evolution and spread of "vaccine-derived poliovirus" (VDPV) type 1 and low risk of VDPV-3.

Acute encephalitis is mostly Japanese encephalitis and summer months are not the season for that. In Bihar’s district of Muzaffarpur, the litchi season is on but I have no information as to what is happening regarding hypoglycemic encephalopathy [referring to the annual outbreak in Muzaffarpur district].