By Sumit Saxena

New Delhi, May 14 (IANS): As the Covid-19 cases jump past 78,000-mark and deaths cross 2,500, a separate statistic -- the number of recovered patients -- may play a crucial role in developing counter strategies to minimize pandemic's infection rate as the country nears the end of lockdown 3.0.

In an interview with IANS, Dr Subramanian Swaminathan, Infectious Diseases Consultant in Gleneagles Global Hospitals in Chennai and Bengaluru said antibodies of the young people who recovered in the first wave of coronavirus may help in treatment of Covid-19 patients.

Covid-19 peak can happen anytime mid-July onwards, and it is likely that Mumbai and Delhi may experience peaks first, followed closely by other metros and moving downstream to the tier 2 and tier 3 centers, added Swaminathan who is also Chair, Transplant ID subcommittee at Clinical Infectious Diseases Society.

He insisted that relying on a century-old strategy, plasma therapy, to treat Covid-19 might work positively, as progress in vaccine development have not been fast enough so far.

Q: In the first wave of Covid-19, mostly young people were infected. Do you think the antibodies of the recovered would help in plasma therapy for Covid-19 patients?

A: Very possible. There are still some unknowns. Can a person survive an illness without development of protective antibodies? We think that is unlikely here, and the vast majority will have good titers at least for some time. For how long? We do not know. At least a couple of months. SARS survivors had good titers for years, so hopefully here as well. Further, will the titers be good enough. Ideally, we would like to do neutralizing antibody titer before use, but that is not available outside research, so one option is to use pooled plasma that is plasma that is pooled from multiple survivors, so that the average titer should be adequate.

Q: Harvesting plasma of recovered patients and then isolating the protective antibodies, which kept them alive, like Takeda -- Japanese pharma giant -- did it. Does this have any future in fighting Covid-19 in the absence of a vaccine?

A: That is similar to what I suggested -- pool plasma and keep it frozen. This can last a long time and can be thawed and used. Trying to purify it may be nice, but increases cost without a significant benefit. This could be used in particular patients, like transplant recipients to prevent immune activation. Based on experience from Ebola and SARS, it is likely to help. Convalescent plasma works when there is a neutralizing antibody for the infection, and in the case of Covid-19, the antibody to the spike protein is what we need; so there is optimism.

By vaccines, you mean active immunization -- that is likely 12-18 months away. Remember that using antibodies is passive immunization. This is routinely used to treat tetanus; after a dog bite to prevent rabies and so on. In fact, this form of treatment is older than antimicrobial use.

For now, I think it shows tremendous promise, but no treatment is effective unless used at the right time. Studies have shown that once a Covid-19 patient ends up on a ventilator, mortality is very high (one study quotes 88 per cent), so that it too late. Identifying those on a bad trajectory and using this early is the most effective method.

Q: Do you see exponential rise in case in May and June?

A: There have been many graphs -- from Johns Hopkins; from Boston Consulting and so on. The effect of the lockdown has been to push the curve further outwards. Depending on the effectiveness from here on, and mechanism of recovery, the peak could happen anytime from mild July onwards. Again, given that we are a subcontinent, we will not be peaking simultaneously all over the country. It is likely that the peaks in Mumbai and Delhi will be first, followed closely by other metros and moving downstream to the tier 2 and tier 3 centers.

Q: Health Ministry had said plasma therapy is not a sure-shot solution for Covid-19 treatment, what is your view on it?

A: Correct. Too many unknowns. Will there be antibody in the plasma? Will the titer be enough? Can we identify the correct patient who will benefit from this? Can this be given at the time when it is most likely to help? Will it be effective? The problem is that once these viral syndromes progress beyond a certain level, the body's immune response is the major culprit. In such situations, the antibody may not do much for the patient. In Covid-19, we now know that there are multiple things that happen in the sick- blood clotting (thrombosis), "storm" of small inflammatory mediators (cytokine storm- IL6) and so on. These cannot be fixed by antibodies.

Q: What are the possible ways to achieve herd immunity?

A: Herd immunity is not a strategy, it is a natural phenomenon. If this did not exist, our vaccine program would fail. For measles, it is 95 per cent; polio about 85 per cent and so on. It is the number of people in a community who need to be immune to an infection, for the infection to die out in that community. For Covid-19, the estimates are between 60-80 per cent.

The only ways to get there are by infection or by vaccine. Therefore till we have the vaccine, it will be difficult. The flattening of the curve will prevent burdening of the system, and reduce the risk of overload to the system, but will stretch out the pain over a longer period of time.

The western world is struggling with this as they have an older population, and they run a greater risk with infection; we have the advantage of a younger herd -- 50 per cent of our population is 25 and under, the very low risk group. If the infection is concentrated in this group, the mortality and strain on the system can be minimized. This is where the concept of reverse quarantine comes in.

If we can place the elderly and those with medical issues out of the general circulation till such time as a vaccine becomes available, this would be a good option, as this could allow services to be restarted. The issue is that once reopening happens, it is likely to take off at a furious pace, which may not be possible to control, and this group is not a water tight compartment.

In the economically weaker section, the elderly are living with the young; in the affluent, the elderly, even if living alone, are unwilling to give up their freedom and mobility, making reverse quarantine challenging. This concept sounds good only if it is extremely of short duration. It appears that we have many months of pain ahead of us, and this approach is unlikely to be practical.