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Johns Hopkins Bloomberg School's Brian Wahl talks about preparedness of COVID third wave, the R factor, the Delta variant and more

The health epidemiologist says most models suggest a third wave, if there is one, would not be as intense as the second wave. But he also warns of potential emergence of a new variant that could better evade the immune system

July 29, 2021 / 12:11 PM IST

A leading health epidemiologist at Johns Hopkins Bloomberg School of Public Health Brian Wahl talks about the preparedness of the COVID-19 third wave, the R factor, the Delta variant and more.

Excerpts from an interview:

How prepared is India for the third wave?

There are two ways to think about being prepared for another wave. First, we need to ask ourselves whether we are doing the things necessary to prevent or mitigate a third wave. This includes minimising social interaction, wearing face masks, improving indoor ventilation, and of course vaccination. Given the transmissibility of the delta variant, we need to take these measures even more seriously, especially after lockdown measures have been relaxed. This is one way of measuring preparedness.

The other way we can think about preparedness is how well prepared the health system is to manage the increased number of cases. Are there enough beds, medical supplies, and health workers? Luckily, most models show that a potential third wave under even pessimistic scenarios would be smaller than the second wave. Nevertheless, we need surge capacity plans that can be implemented—whether for COVID-19 or another health emergency.

Some states have started experiencing a surge

Yes, we are seeing some states experiencing surges in confirmed cases. There are many factors that contribute to whether cases are increasing or not. One important factor is the proportion of the population that is susceptible to the virus. In places where COVID there is a greater proportion of the population that is susceptible—for any number of factors, including stringently followed COVID-19 behaviours—this could be contributing to this increase in cases.

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COVID-19 Vaccine

Frequently Asked Questions

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How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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Is this a reflection on an impending national-level third wave? Can we still stop it?

In previous waves, some states have served as harbingers of surges elsewhere in the country. Will this continue to be the case in future waves? It is difficult to say. There are multiple reasons why these states saw a rise in cases first, including cases being imported from outside and the emergence of new variants in these places. However, susceptibility is likely to vary from one location to the next now and so therefore a rise in cases in one place might not necessarily correspond to a subsequent rise in cases in another part of the country.

India is still way behind its vaccination targets because of the huge population. What should be done? Will this make a third wave more susceptible?
Susceptibility is indeed one of the main drivers behind whether cases are increasing or decreasing. There are really just two ways to decrease the proportion of the population that is susceptible to COVID-19. The first is natural infection and the other is immunisation. We prefer the latter for many obvious reasons. This is why it is important to increase immunisation as quickly as possible. The recent results of the national serosurvey conducted by ICMR showed approximately 68% of the population older than 6 years have antibodies to the virus that causes COVID-19. For a highly transmissible virus like the delta variant, this is sufficient for another wave. Therefore, vaccination is that much more important.

What is the R number? What are the factors that determine the R number? Can they be a reflection of a wave?

R stands for the reproduction number. In simple terms, the reproduction number is the average number of new infections arising from one infected individual. When cases are increasing, R is greater than 1. When cases are decreasing, it is less than 1. There are four main factors that contribute to R. They are how long an infected individual is infectious, how many opportunities there are for infections to occur, the probability of transmission given an opportunity, and the proportion of the population that remains susceptible. This can be summarized easily using the acronym DOTS. All factors are necessary, and so reducing any of them to 0 would extinguish an epidemic. However, this is not feasible in any environment right now. But some of these factors are mutable and therefore can be addressed. We can decrease opportunities for infection through COVID appropriate behaviors, decrease the probability for transmission given an opportunity through mask wearing and improved ventilation, and decrease the proportion of the population susceptible to the virus through vaccination.

Many states have eased social restrictions because of economic reasons. What should be done or limit a third wave. Is it fine to open social places like restaurants and gyms?

Nobody wants a lockdown and it is critically important to take into account the secondary effects of lockdown measures, including economic effects. This has been a challenge faced everywhere in the world during the pandemic. To limit the probability of transmission in settings like restaurants, we need to also consider improved ventilation.

Is there any way to end the pandemic and its recurrent waves? Should vaccines be made compulsory like in some countries?

COVID-19 vaccines are our best tool for ending the acute phase of the pandemic. Whether they should be mandated or not is a difficult question and invokes a perennial consideration in public health—the tradeoff between, on one hand, respecting autonomy, for example by allowing an individual to make their own decisions regarding COVID-19 vaccination, and, on the other hand, beneficence, or the moral obligation to protect others, for example through widespread vaccination. Personally, I think there is a strong argument in favour of making vaccines compulsory for some professions, like health workers, and to do some activities. But these are ultimately difficult decisions and reasonable individuals can have differing opinions about these steps. Only two or three countries—have made COVID-19 vaccines compulsory for all adults.

Do you expect the third wave surge to be less intense than the second?If there is a third wave, most of the models show that it would not be as intense as the second wave. This is based on the assumption that a relatively high proportion of the population already has antibodies, as was demonstrated in the recent national seroprevalence study I mentioned earlier. The wildcard, though, is the potential emergence of a new variant that could better evade the immune system. Luckily, the vaccines we have now appear to remain highly effective at reducing severe cases and deaths due to all variants, including the delta variant. The more a virus replicates, the more opportunities there are for new variants to emerge. So, increasing vaccination can help limit the emergence of new variants and so should be a priority. Because variants can emerge anywhere in the world and travel to India and elsewhere, the global community should work to ensure the highest possible vaccine coverage for all populations around the world.
Vanita Srivastava
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