Mumbai: India has now administered more than 1.88 billion Covid-19 vaccine doses, covering a substantial portion of the population. In comparison, just a few (27 million) have received a third booster shot, or precautionary dose. Nevertheless, the number of new Covid-19 cases remain low at the end of April 2022, compared to other countries.

Many of the cases being reported in cities are also asymptomatic. Many more are contracting Covid-19 but are either not getting tested, or are testing themselves at home using rapid antigen test kits and not reporting the results. The daily Covid-19 case numbers are therefore not accurate in terms of assessing the extent of disease prevalence at sub-national or national levels, and the role of vaccination or natural immunity on caseload.

With fewer Indians taking a third booster dose, compared to other countries, will this mean we could see Covid-19 cases rise again, or is it now a disease we've come to live with? Should those experiencing flu-like symptoms be concerned about mistaking Covid-19 for the flu? To address all these questions, we spoke with Anita Mathew, a senior consultant physician and infectious disease specialist at Fortis Hospital in Mumbai, and Rommel Tickoo, director of Internal Medicine at Max Super Specialty Hospital in Delhi.

Edited excerpts:

Dr Mathew, how are Covid-19 patients presenting in your hospital?

AM: We don't have a Covid-19 centre right now in our hospital. We do see some out-patients come in, but the numbers are few. Maybe every second or third day, I might see one Covid-19 positive patient, compared to most patients being Covid-positive earlier. So we are fairly okay in terms of the number of patients that we are seeing in Mumbai.

Among the Covid-19 patients coming in, what kind of symptoms are you noticing?

AM: These are typical viral symptoms: a bit of a sore throat, or fever, or body ache, but nothing much. None of those are typical of what we used to see earlier on with Covid-19, like loss of sense of smell and taste. Nine out of 10 patients do not require admission to the hospital, nor do they complain of breathlessness. We're not really seeing those kinds of patients at all. We're predominantly seeing cold, cough, fever and occasionally, loose motions. So we are seeing very mild disease, as of now.

Would all the Covid-19 patients who come to you be vaccinated?

AM: Most patients have been vaccinated with both doses, but there are some who have had Covid-19 in the past as well, in the year before the last wave. They have typically very mild cases.

Dr Tickoo, how is the Covid-19 virus presenting itself in Delhi?

RT: Though there have been a 1,000-odd cases in Delhi for the last few days, almost all had very mild disease and are getting better on their own, as of now. I'm sure there are more cases because people are testing at home and we don't take that into consideration. A lot of people are actually not testing at all, because they believe that they will get better in two to three days, and that's actually what's happening. So we are in a good space, as of now, but let's be careful. Let's wear a mask because you never know when the cases will go up.

Assuming that most of your patients are vaccinated, would it be fair to assume that Covid-19 vaccines are working effectively?

RT: Of course. Vaccines have worked in Delhi. The majority of the eligible population is vaccinated, and that's why they are having mild symptoms. We all know that vaccines can't prevent you from getting infected, but they prevent hospitalisation, severe disease and death. That's what we are seeing. As the majority of people in Delhi and in India are vaccinated, that's why we are not facing those problems which other countries all over the world are facing. The vaccines definitely play a part. Now, I would also insist that those who are eligible get a booster dose, because it gives you another level of protection. We all know you might still get Covid-19, but you will not land up in hospital. So vaccination is a must. It has worked. At least 1 billion people have got one dose in India. We've done it aggressively, we've done it well, and that's why we're reaping the benefits of vaccination.

As someone who treats infectious diseases, what's your sense of how the infection could hit us? Let's say the vaccine fights back and the disease goes away, but then we get infected again because, across the country, we are at far greater levels of exposure to people, attending weddings, going for movies, to malls, and without masks. What does that mean in terms of the way the virus could spread, and our body's ability to resist it?

AM: We have two distinct mechanisms by which the body is known to fight against infection. One is the response with the antibody, what we call a B cell immune response. Then you also have a far more complex response called a T cell response. These T cells are your memory cells which remain and are in a position to mount a response whenever the infection or the offending organism comes in contact with the body. This is also the mechanism by which you look at a vaccine. That's how the polio vaccine and all the other vaccines have been prepared, with the help of this T cell response that gets initiated once you give those booster doses. These are especially important and these are your normal fighting mechanisms which will come into play. So that probably is saving us from a lot more infection than what you would end up seeing in a country with a humongous population like ours.

Having said that, this is where we need to understand that this particular coronavirus is what we call an RNA [ribonucleic acid] virus, so it's similar to HIV in a lot of ways, in terms of the fact that they can keep on mutating. That is the reason why we do not have an answer for a final, complete vaccine. So we may end up requiring some more shots in future. Maybe it could be incorporated with an [annual] flu shot like we normally do. We don't know how it's going to pan out in another year's time. But we do know for sure that the flu doesn't infect the majority of individuals. It could be a subclinical infection, which means you could have an infection which is mild enough for you to not even show a response in the form of a cold, cough or any kind of symptom. A similar thing must be going on right now in the background, among the community. We are not really going ahead and testing for it. So I do believe we have some amount of herd immunity for the present Covid-19 variant at least, and that is the reason we are so far in a better space than many other countries.

Dr Mathew, India started vaccinating in the second week of January 2021. Many people who got their first dose in January 2021 got their second dose between March and May 2021. Thus many people, particularly in the mid-age group, were vaccinated over a year ago. Is that something that worries you?

AM: Not really, because two doses of a Covid-19 vaccine also mount a good immune response. Of course, a booster is something that you would be really looking at. But we have something called memory T cells. We're not really sure of their functions and we have not had robust data on Covid-19-related T cell memory response, but I do believe that there will be some response that a [vaccinated] body would initiate when it comes in contact with the Covid-19 virus. There would be some level of protection. Whether the protection is going to be robust enough is something that I can't really commit to at this stage, but I do know that patients will mount a response and there will be some level of protection. However, if you take a booster, obviously the level of protection is far higher. So yes, if they could ramp up the services and go ahead and vaccinate even the people who have taken the last dose six months ago, I think that will help immensely.

Dr Tickoo, if I got my last Covid-19 vaccine dose in May 2021, is the vaccine still working? To what extent should I assume that it will continue to protect me?

RT: Even if you've taken two shots, it gives you enough protection, and you won't land up in the hospital, you won't have severe disease. But there's enough scientific evidence that says that the effect of the vaccine wanes after five to six months. That's why we need the boosters. You might still end up getting an infection which is mild, but why not boost your immunity, and give another layer of protection to yourself? If you've taken the last dose in May 2021, then after six months, I would say, you should get a booster. That's how I would look at it, instead of nine months. We do have to look at the logistics, at the manufacturing, whether we have enough doses, we also have to give the first dose to a lot of people. But having said that, I would say we can reduce [the booster dose interval] to six months now and whoever is eligible should be taking it. We have enough evidence that vaccines do work, all over the world, so there should be no hesitancy now when it comes to vaccines. More than 80% of people in India have had Covishield, the rest had Covaxin. There's so much data, looking at almost 1.85 billion doses that have been given. I don't think there should be any argument or debate on the efficacy of the vaccines. When it comes to the booster, everyone should take it.

We're lucky that even children will be getting vaccinated. Now we have two vaccines which have been given approval. That's one section which was not vaccinated and soon they'll also be vaccinated. But again, in children the disease is mild, and we don't see too many complications. So overall, it's looking far better for India than the rest of the world. But again, we should keep our fingers crossed. We should keep doing what we are doing.

So you're not seeing anything today or hearing of cases coming to hospitals, even if relatively mild, which could be an outcome of reduced vaccine efficacy? Is it too early to judge that?

RT: It's too early to comment on that. But I think [full vaccination] does give you enough protection. It doesn't become redundant after five to six months. It gives you enough protection, but if you have a booster available, why not boost your immunity? This might become a norm, as Dr Mathew said. Maybe you will have to take it once a year also, the way you take a flu shot. Covid-19 is almost becoming endemic now in India. If you look at the last wave, after that there have been sporadic cases here and there. In a vast country like ours, there will be ups and downs. We're not looking at numbers now. It's beyond that. Now we have to look at hospitalisation rates and mortality, and it's heading towards becoming endemic in India. We'll have to live with it. But again, do wear the mask for the next six months.

Dr Mathew, between immunity born out of prior infection versus vaccination, what seems to be working better in the cases that you have seen?

AM: There is enough data to suggest that if you've had an infection in the past and natural immunity, that probably gives you better protection compared to a vaccine. But that doesn't take away from the fact that the vaccine does work. I have taken my three shots, and in all the three waves, I have not had Covid-19. So what protected me was vaccination, masking, Covid-appropriate behaviour and, of course, the grace of God. The vaccine does help, your mask helps big time. Both together should be helping you.

There are patients who are naysayers, the fence-sitters who do not want to take the vaccine, who would say that natural immunity is better. But the cost of natural immunity sometimes is an even higher level of morbidity, which is severe illness and running to the hospital, probably requiring a ventilator. Occasionally, a person can die. So I think it's better to go for vaccine-related immunity rather than natural immunity. Having said that, all natural immunities are better than vaccine ones. That's across the board.

Those who are consulting you, are they in the 30 to 60 years age range?

RT: The majority are in that age group because they are the ones who are travelling, they're going to Goa, they're going for weddings and celebrations and they're the ones who actually end up bringing Covid-19 back home, and then the parents and grandparents get it. It's the younger lot who gets it home.

AM: The majority of patients are between 35 to about 65, that's the age group that we are seeing. We do see a lot of paediatric cases, children coming with flu-like symptoms. Since schools have opened up completely, these numbers did go up. These kids have had some kind of an infection. I don't think everybody's been swabbing all the kids to see whether they have Covid or a non-Covid, flu-like virus. But I think some of these cases would have been coming from the community and they may be getting it back home too.

Dr Tickoo, if you were to look at the age groups of patients that you've been seeing, particularly in the last two to three months, with or without receiving full immunisation or booster doses, are there any variances in response?

RT: I haven't seen that. If we talk about Delhi, the majority of the adult population has been vaccinated and I haven't seen any difference in the symptoms or the presentation of patients. Even now I'm seeing four or five patients a day virtually, and they all seem to be having the same flu-like symptoms, nothing different in the last month or two. I haven't had even one patient who needed steroids or hospitalisation. And I think almost all of them were vaccinated. So the vaccine does prevent you from getting severe disease. But yes, there are people who after vaccination have been infected, twice, thrice also. But again, it behaves like the flu. As long as it behaves like the flu, it doesn't really matter.

Are the 60-plus age group, and with comorbidities, still the segment under greater threat?

AM: They are obviously going to be under greater threat because age is one of the major factors. Your immune system doesn't behave appropriately after a particular age, so they are obviously going to be at a higher risk at any time point. So the older you grow, the more likely that you're going to have more complications in terms of the disease.

Would your advice be different for different age groups at this point of time, given that the economy has opened up?

RT: We have to live with it. Schools have opened. So many children are getting infected but again, all of them are getting better. They have mild, flu-like symptoms. So the advice wouldn't be different. It will be the same. Whoever is eligible for vaccination, please go for vaccination and wear a mask. When it comes to children, it's difficult for them to wear a mask. But for adults, vaccination plus masks is what you should be doing. It's not practical to wash your hands very often or to maintain social distance. The way things are right now, everything is back to normal and we have to live with it. We have to accept the fact that this virus is here to stay for some time. But as long as we don't have a new variant, which is mutated, causing severe disease, it's fine. Just take the precautions which we've been taking for the last couple of years now.

What are the kinds of data inputs that you would look at to help you understand and anticipate what is likely to come, whether it's the virus itself or its behaviour or, for a better understanding of how the human body is responding to this virus?

AM: What we would definitely need is more genomic studies. Rather than doing it as a one-off, we probably need to do the genomic [sequencing] for most of the patients who come to the hospital with this particular disease. Maybe also run some kind of epidemiological survey to really look at what's happening in the community, at a time when patients are really not falling sick. This is something that we would really need to be able to determine where we are heading and what kind of responses we are going to see in future.

RT: The virus keeps growing and we never know when a mutation will happen and how the virus will behave. So genetic sequencing is something which we have to do to keep track of the virus, how it evolves, what are its characteristics, what are the mutations, and how it's going to behave in the future. We have to pick it up early. That's why it [Delta] hit us so badly. But having said that, it was a bad variant, a bad mutant. I think we have learned enough from our experience, and from the experience of other parts of the world where people are still facing a deluge of the virus. Right now, I think we're in a good place, and we should be taking those precautions and keeping a track of the virus, being vigilant. We don't have to think that it's dead and gone. It can come back any time. A new and monstrous mutant can hit us again. So keep at it.

Is there less local data that you would like to understand how things are moving, either in the public health or in the clinical context?

RT: I don't think there is any data which tells us how the virus is going to behave in the future. That's something which nobody can predict. We have to be at it, we have to take all the precautions. My gut feeling is that over a period of time, the virus is sort of becoming weaker, and maybe it will eventually die down in the next six months. It's not going to be there forever. So six months, eight months, and gradually, maybe just get out of the country, and out of the world. But till then, we have to keep at it. We can't get complacent. I don't believe in these mathematical models that there will be a fourth wave in June, or there'll be a fifth wave in October. I don't think anybody can predict these waves. Nobody could predict the Delta wave. Nobody could predict the Omicron wave. So how can we predict that at one particular point of time, we'll have a wave? Actually, nobody knows. So we'll have to see how it unfolds in the next few months.

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