"Every time R goes above 1, it could potentially signal a beginning of the next wave," says virologist Dr Gangandeep Kang.
As over 8 states cross the R-rate of 1, is India headed towards the 3rd wave of the COVID pandemic? FIT speaks with Dr Gagandeep Kang from CMC Vellore, to break down India's COVID numbers, understand the situation in the state of Kerala, behaviour of the virus as we go forward and India's vaccine strategy.
How concerning is India's R-Rate? What does it signal for India's 3rd wave?
Dr Gagandeep Kang: R-rate measures how many infections one person is passing on in their community. And any time that number is above 1, it is an infection that will continue to grow in the population.
If we look at R0, that is the rate of spread you have when the entire population is completely susceptible, and for SARS COV 2, that R0 was calculated to be about 2.5. With the Alpha variant, that was 1.6 times more transmissible, and the Delta variant which was even more transmissible, so now that gives you a potential R0 of around 6.5 to 8.
That has been reduced to an effective reproductive number that we should aim to keep below 1, but is just above one in some states. This is a signal that you should do something about it.
It's important to look at in which population is the R being measured. If you are measuring R in the general community and it is 1.2, you need to really worried about. But if you are doing targeted testing and looking at controls, if you are looking at symptomatic cases, then you don't have to worry so much about it being above 1, because it is not representative.
What explains Kerala's consistently high numbers? Is low sero prevalence a good enough explanation?
Dr Gagandeep Kang: Kerala certainly has a large proportion of the population that is susceptible. It is also a state where population density is relatively high. What the sero positivity rate tells us, and it is important to remember that is will include people who have been infected and those who have been vaccinated, among those who are vaccinated, you expect protection, among those infected, you also expect protection. But there may be a number of people who may be protected, but not testing positive in sero surveys because of the waning of antibodies.
How do you protect this large susceptible population in Kerala?
Dr Gagandeep Kang: Routine public health measures, testing, monitoring etc becomes very important. And Kerala has done a reasonable job of doing that. As cases rise, they'll have to ramp up those efforts even more.
You have to ensure to prevent crowding. Kerala had decided to open up for Eid which wasn't a good public health measure. Now with Onam coming, so they need to be even more careful.
Kerala needs to push vaccination. Supplies are short, but you have to get creative with your vaccination strategy.
We are not experimenting and documenting enough on vaccination strategy.
Given India's sluggish vaccination rate, how do we ensure a large numbers are not impacted by the 3rd wave?
Dr Gagandeep Kang: The question really is what is sluggish? If we look at low and middle income countries, we are actually doing pretty well as proportions. We are doing well in terms of numbers. We are keeping pace with supply. The problem really is there isn't enough supply. Every effort we can put in has been put in.
Until we get people vaccinated, we have to continue to apply public health measures. Masking has to continue. Ventilation will continue to be critical.
Between the vaccination and the horror of the second wave, when we had such a high rate of infection in the country, we are actually not in as bad a position as many other places.
If you get a variant that breaks through prior immunity, we will be back where we started. But hopefully that will not happen.
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