Even as the second wave in India seems to have already peaked, many States still report high test positivity rates suggesting more cases remain to be detected. The slow down in daily cases has been mainly due to strict lockdowns in many States. With the alpha (B.1.1.7) and delta (B.1.617.2) variants widely present across the country, and the possibility of new variants with higher transmissive ability getting imported or emerging in India cannot be ruled out, the possibility of a third wave appears to be real.
In an email to The Hindu, Dr. Bhramar Mukherjee, Professor of Biostatistics and Epidemiology at the School of Public Health, University of Michigan, and Dr. Giridhara Babu, Professor of Epidemiology at the Public Health Foundation of India (PHFI), Bengaluru discuss when a third wave is likely to begin in India, how to identify one and the measures required to achieve vaccine equity to reduce the daily cases and deaths in the third wave.
With the second wave appearing to have peaked in India. At what stage can it be said that the second wave has been contained?
Bhramar Mukherjee: The seven-day test positivity rate (TPR) is at about 7%, effective reproduction rate is at 0.68, so I think as a nation, one can say that the wave is in decline. But with 1,30,000 cases and 2,500–3,000 deaths every day, I cannot say it is contained. There are large States still registering a significant number of cases with TPR of over 15% such as Karnataka, Kerala, Tamil Nadu, Andhra Pradesh, West Bengal and Odisha. Then there are smaller States with high TPR such as Goa, Manipur, Nagaland, Sikkim, Meghalaya and the north east cluster.
Giridhara Babu: It is projected that the daily case count will decrease beneath 50,000 around June 13. Assuming that we will maintain over a million tests each day, we might see daily test positivity at the national level to come below 5% during June 13–20.
Both alpha (B.1.1.7) and delta (B.1.617.2) variants were the main drivers of the second wave in India. Will India experience a third wave and worryingly more waves in the future?
Bhramar Mukherjee: This is probably not the last wave and these are not the last set of variants. We have to stay prepared for the future. What happens when we see another uptick or outbreak is to a great extent in our hands. We know how to fight this virus. Even with the second wave, if we had acted in mid-March, thousands of lives could have been saved. My point of view is that we need to stay prepared for the nth wave and the zth variant. We have to stay prepared for outbreaks for the foreseeable future. With accelerated vaccination, we can fight back and turn a peak into a bump.
Giridhara Babu: There is no doubt that there will be another wave around November–December. Any outbreak of infectious disease will occur when the build-up of susceptible persons reaches beyond a critical point. Super-spreader events will only facilitate reaching this point earlier. In addition, variants such as delta can spread faster than alpha. Therefore, it is only a matter of time.
What indicators should be looked for to call it as the beginning of a third wave?
Giridhara Babu: As we emerge from the second wave, seven-day average growth rates of cases and deaths should be regularly monitored. In order to have objective monitoring, the testing levels have to be stepped up, and the syndromic approach of surveillance has to be strengthened and reviewed in all the states. Whenever we observe the occurrence of cases clearly in excess of the previous weeks, we should be on high vigil to detect clusters and investigate them both for epidemiological and genomic investigations. Other indicators to help in the process are test positivity rate (doubled in a week subject to no changes but high testing levels) hospitalisation rates (doubled in the corresponding seven consecutive days). The centre should provide guidelines indicating when we can call a new outbreak as the next wave.
The following four prerequisite criteria are necessary to declare the third wave. First, the second wave should have been contained, which means that the reproduction number is below 1 for two weeks. Second, the low rate of infection has to be sustained for at least one month. Third, see if cases are increasing steadily for over two–three weeks, and finally, check if cases are increasing steadily after crossing the basic effective reproduction number (RT) of 1.5.
The government is projecting 10 million vaccinations per day by mid-July. Over 28 million have been already infected naturally though the actual numbers will be many times more. So what is the minimum percentage of the population that needs to be vaccinated to prevent a third wave?
Bhramar Mukherjee: We need to keep India’s age pyramid in mind. Forty percent of the Indian population is in 0–18 years for whom we do not have any vaccines available yet. If we can get Pfizer vaccine for those aged 12–18 years and for pregnant women, and Covaxin gets approved for kids that will be a big help to the immunisation strategy. Data also shows (a recent paper in Nature Medicine ) that in people with past COVID-19 infection, one dose can produce similar antibody levels as in an infection-free person with two doses. If a large fraction of India is infected, then one dose of vaccine post infection will likely give good protection.
I also hope we can get some one-shot vaccines. This could go a long way for India where vaccine adherence is an issue along with a large population.
Giridhara Babu: The 1.3 billion plus people in India constitute the source population at risk of infection. We have a long way to go. Ideally, more than 70% of people should be protected with the vaccine in order to have lower peaks of the waves. I would not consider infected as a component of this estimation, as evidence suggests that even those who are infected should be vaccinated.
What vaccine strategy is needed to protect the vulnerable people in the 18–44 age group, particularly the urban poor and those living in rural areas?
Bhramar Mukherjee: For urban poor and rural areas, we need mobile vaccination, door-to-door campaigns, seeking buy-in from religious and community leaders, and vaccine clinics in front of places of religious gathering. Employers encouraging and providing vaccination to employees, even supporting and ensuring vaccination of all household help in urban metros goes a long way. People with comorbidities and special health conditions should have a priority.
Giridhara Babu: Any person with comorbidity should be part of the vulnerable population, irrespective of the age group. In addition, the parents, those who work in occupations with high people contact, school teachers etc., should be prioritised for two doses. Every eligible person should get at least one dose by December.
Over-reliance on the CoWin platform for the 18–44 age group is causing vaccine inequity even in cities. Can COVID vaccination be carried out without relying on CoWin in the rural areas to reduce vaccine inequity?
Giridhara Babu: The digital divide is a significant barrier created by the Government, which worsens the existing health inequities. India is a global leader in conducting vaccination campaigns. These are done by a bottom-up approach for micro-planning to include all the eligible beneficiaries without missing a single person. Also, mobilisation campaigns are important to alleviate the concerns related to vaccination and ensure that people visit the vaccination sites in time.
Since a surge in cases was first seen in big cities in both the first and second wave, will it be prudent to increase vaccine coverage in big cities to reduce the possibility of a third wave? Will such an approach lead to vaccine inequity between cities and between urban and rural areas?
Bhramar Mukherjee: First of all, the second wave has penetrated rural areas. The rural–urban vaccine inequity will happen even if you try to prevent it, so the governments have to take vaccines to rural areas. We have a strong immunisation framework using community health workers in rural areas. So we have to activate all our powers to get through this.
Giridhara Babu: That’s not the correct characterisation. The lower reported numbers from rural areas reflect the poorer testing and sparse population density in rural areas. There are also no hospitals in rural areas. If anything, it is important to ensure that people in the rural areas are well covered in the vaccination programme.
India has so far not undertaken any large-scale, real-world study to understand the effectiveness of the two vaccines against the alpha and delta variants. How concerning is this?
Bhramar Mukherjee: Why do we have vaccine data against new variants from the U.K. but not India? India should be providing data on effectiveness of the Covishield vaccine against the delta variant, but all we have is based on U.K. studies. How is the government assessing vaccine effectiveness studies? Are they employing test negative designs? How many breakthrough infections have happened with one dose? How many fatalities, hospitalisations? These are key information that the world needs to know from India.
We have to do careful studies of vaccine versus variant interface and understand the immune escape properties of emerging variants. We have to design studies to make sure if we need another booster dose of the vaccine, we get one before vaccine induced immunity wanes. There are still big unknowns and uncertainties in this pandemic that we need to first recognise and then prepare for.
