Airborne Spread & COVID Vaccine: Tutorial With Dr K Srinath Reddy

A COVID-19 vaccine not likely before a year, says Dr K Srinath Reddy

3 min read

From coronavirus now being recognised by the World Health Organisation as being airborne, to India's vaccine claims and finally reading terminology like recovery rate, positivity rate and case fatality ratio, Dr K Srinath Reddy, president of Public Health Foundation of India, shared his insights in an interview with FIT.

Dr Reddy also spoke about strategies India needs to adopt to prevent its rise from no.3 in global COVID-19 rankings to no.1.


Why has WHO Been Reluctant to Recognise that Coronavirus Could be Airborne?

Dr Reddy: "The evidence has been around for the last 3 months or so, after some high resolution images showed formation of aerosols in indoor places. From the past experience with SARS, it was thought this is majorly a droplet infection. But recognising that SARS was essential an infection in the lungs, this virus, besides the respiratory track, has a presence in the nose, throat and sinuses, and can discharge itself easily in loud singing, shouting or performing, it should have been understood that in indoor places where ventilation was low, the aerosols could hang around in the air for a few hours."

Referring to super-spreader events that originated in bars and restaurants in several countries that opened up, Dr Reddy said that the conclusion that coronavirus is airborne is inescapable.

Speaking about how this would impact policy making - Dr Reddy said that firstly, we have to realise that the pillars of our fight against COVID-19, physical distancing, wearing masks and hand hygiene remain most critical. But when it comes to schools, restaurants, bars and offices, open ventilation is key. In the absence of the above, you have to wear masks indoors in public places.

“Maintain as much open ventilation as possible. Whether its schools or offices, keep air flow as much as possible, and if your office architecture does not allow for open air flow, wear masks indoors,” Dr Reddy added.

When is a Vaccine Realistically Going to be Available?

Dr Reddy: We need a vaccine that is both safe and efficacious, and we need a vaccine that can meet global demand and at a reasonable cost. A large phase 3 randomised control trial will itself take you till end of the year - after that production and supply chain will kick in and will require tremendous effort to deliver it to various parts of the world.

Such a vaccine reaching most of the world before mid-next year is very low. But India has an advantage in that we do have a very good production engine for ramping up production and distribution. If India's vaccine was proven to be efficacious we do have that advantage. But if it is a vaccine from any other part of the world, we are depended upon global availability demand and willingness etc.

Understanding Numbers: A Tutorial

What is Case Fatality Ratio? Where Does India Stand?

Dr Reddy: When you look at any number, whether cases or deaths, you have to look at the denominator as well. When you compare countries or even time period, where was India in March and where is India now, you have to divide the number with population size. Deaths per million becomes very important. If you look at the numbers from March to now, the numbers do look disturbing at the moment. You also have to age-standardise these deaths and compare countries accordingly. Finally, we have to take the learnings from areas where the fatalities have occurred and apply those learnings in parts of the country where numbers are still rising, to ensure deaths remain low in these areas.

What is Positivity Rate? Is India’s Numbers a Good Indicator?

Dr Reddy: If we standardise the criteria of testing, and standardise combination of testing methods, then it is something that can be very important. Antigen testing will give a large number of false negatives - leading to all these tests having to be reconfirmed with RT PCR. So, suddenly, if you bring in a large number of antigen tests, and you say positivity rate has come down, that doesn’t always carry conviction.

What is Recovery Rate? Does it Even Matter?

We are relying on the fact that large parts of India are not throwing up too many new cases, and the active cases that are there are recovering, then that’s a good indicator. But if we convey that 60% or 70% are recovering, then that sends out a disturbing message to the public. Recovery rate is a cumulative number, as we progress, we know that 97% people will recover either fully or will have some long tail symptoms.

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