Dr. Samiran Panda , Head, Epidemiology and Communicable Diseases, Indian Council of Medical Research (ICMR), and Director, National AIDS Research Institute (NARI), speaks exclusively to The Hindu and explains about the possibility of a third COVID-19 wave and how future waves can be prevented.
How imminent does a third wave seem for India? This when the vaccination rate has slowed down and also the rate of reduction of new COVID-19 cases has stagnated?
There have been increasing speculations on the possibility of a third wave of SARS-CoV-2 infection in India. If one responds in affirmative — which I think is a distinct possibility although not inevitable as it is dependent on the scale and quality of appropriate public health measures — the volley of questions that follow are when, how big and how long will it stay?
The modelling study we conducted from the Indian Council of Medical Research in collaboration with the Imperial College, London, yielded multiple outcome scenarios in this regard ranging from an onset of a third wave in late August, 2021, to October this year.
The time to reach its peak, however, would take four more months and could even go to as far as mid-2022. One should, however, note that the peak of the third wave may not be as severe as the second wave and all these possibilities are dependent on a number of factors such as — waning of immunity acquired by us following natural infection or vaccination, emergence of a SARS-CoV-2 mutant that is able to escape the immunity we have acquired so far, emergence of a viral variant, which is more transmissible or easing of restrictions that were instated in some of the States following the second wave that started gaining its momentum in February 2021.
Natural immunity is said to last 6-9 months. Through vaccination, people get protection for 9 -12 months. If the second wave peaked in mid-May, then how could a third wave hit so early?
First, we need to understand that the different States in the country witnessed a different intensity of infection. During the said second wave of COVID-19 in India, 80% of the caseloads were contributed by about 10 States. So, there is still a large proportion of the population in other States that is vulnerable to catching the infection.
Second, when the cases rose to a concerning height in Delhi and Maharashtra and a few other States, these States imposed restrictions to contain the spread of the infection. Drawing upon these examples, the other States where the cases were not so high also imposed similar restrictions, curbing the infection curve at an early stage. But now these States have to be very careful while lifting the restrictions as their population has not been exposed to the virus.
Any carelessness can lead to a sharp surge and in such scenario the issue of waning immunity becomes irrelevant as by and large considerable proportions of the individuals in these States did not have exposure to infection and even if they had the first and second wave of infection were small enough to leave a considerable proportion of the State residents vulnerable.
A third wave in such a situation can make its appearance felt as early as late August, 2021.
Delta variant was the dominant strain during the recent wave. Do you think it will be the emergence of any new mutant that would lead to another surge?
There are multiple factors that could contribute to the surge in the number of cases. The CHROMIC (Collaborative Health Research On Modelling by ICMR & Imperial College) model highlighted four such scenarios in this regard.
First, the immunity that people developed through the natural infection or vaccine fades away, making people vulnerable to re-infections, second the emergence of a new mutant which is capable of escaping the immunity, third the emergence of a new mutant which is more transmissible and last a surge is possible in States which imposed effective State-level lockdown at an early stage during the second wave.
These States didn’t allow the Delta variant to spread during the recent outbreak and need to be careful while lifting the restrictions.
So, would it be a second wave for these States?
Each State needs to characterise the course of SARS-CoV-2 infection progressing within its territory and spreading in its population. Only then it will be possible to assign a number against each of these waves appearing in a State. India is a large country and different parts of the country are in different phases of the COVID-19 epidemic.
For example, in Delhi it was not the second wave, rather it was the fourth upsurge and the heights of these waves differed from each other depending on the intensity of spread of infection vis a vis concurrent intervention measures. It is important to appreciate such heterogeneity so that State-specific intervention measures can be appropriately planned. The way to do so is to examine local level data to inform programme and to work with the community to implement interventions.
And even think of now, it is told that we are in a declining phase of the second wave in India. That’s the country average, which tells us so. The problem with such averages is that they not only get influenced by extreme values but also by frequent occurrences. But State-level pandemic management plan cannot benefit from such averages as this is an overall country scenario. The virus has not disappeared from the country and while it is maintaining a quieter profile in some corners, somewhere else it is causing havoc. The States in the north-eastern region of the country, for example, or Kerala, are still witnessing the second surge moving upwards or in Maharashtra declining to go down. Understanding the local context, congregations and compulsions are therefore important.
Can we prevent future waves?
Yes, it can be prevented. But for that, we need to understand that there is no one India when it comes to the spread of the infection. Different regions are in a different phase of the pandemic. Health is a State subject, and so to prevent yet another surge it is important for authorities to assess the situation in different districts and take appropriate district specific measures after a careful epidemiologic analysis.
Second, by ramping up the vaccination we can reduce the severity of the disease to a great extent. The CHROMIC model clearly shows how vaccination can help flatten the curve of the third wave at population level.
Third, by avoiding the mass congregations — we will be able to take away the opportunity from the virus for spreading. In short, we need to avoid situations that can help the reproduction rate of the virus to go up.
And finally, through INSACOG, the government is keeping a vigil on the emergence of new viral variants. Considering such information together with sentinel surveillance data at the district level is the need of the hour. In order to be able to outsmart the virus named SARS-Cov-2, we have to have smart data usage plan that could inform pandemic containment measures at the peripheral outposts in which active engagement of the community is a must.