Inactivated vaccines do not have a very good reputation, but Covaxin data looks promising: Expert

How effective will vaccines be against various mutant strains of SARS CoV2 virus? Will a third booster dose be needed?

There are no clear answers to this. The data suggests that two doses of mRNA vaccines are needed for good protection against the Delta variant, but it is not clear how long that immunity lasts, especially among the immunosuppressed or elderly. Israel is seeing some disease in vaccinated people and has started a third dose. However, the priority is to make more vaccines for the primary course rather than a booster, because even if vaccinated people get sick, it is less likely that they will die. Though I must say that we are moving to a situation where an updated vaccine could be used. Flu vaccines are updated every year, so we may end up in a similar situation with Covid-19. Vaccines will still be protective to an extent against severe disease and against most mutant strains at present, but we need to keep monitoring.

Which among the bouquet of vaccines is the most effective. Can a combination of vaccines work

Which among the bouquet of vaccines is the most effective? Can a combination of vaccines work?

I think most vaccines are effective against very severe disease and death. But there remain questions on duration and breadth of immunity. Data shows that AZ and Pfizer work well when mixed: one dose of each… though it may depend which one is given first. So, mixing vaccines may be a good thing and may work better than two doses of the same vaccine. Inactivated vaccines do not have a very good reputation, but the Covaxin data looks very promising. It is important to look at effectiveness against severe disease and not mild disease. At the severe end of the spectrum, vaccines start to converge in effectiveness.

How severe are breakthrough infections in terms of duration of long Covid?

There is not much data on long Covid in vaccinated people – though the Israelis have published a small study. It is important to have a control group (i.e. vaccinated people with no breakthrough infection) to see which of the quite vague symptoms of long Covid are truly due to the breakthrough infections. Biologically, I see no reason why vaccinated people would be spared long Covid if infected.

Dengue and chikungunya are endemic in India. Diagnosing the vector-borne diseases may be challenging as there may be an overlap of symptoms with Covid-19. What are your concerns?

Dengue and chikungunya are not known for respiratory signs, and the cases can be picked up as one of the causes of acute fever. Hopefully, testing for vector-borne diseases will pick up since one really needs a good idea of where the virus is and where it is going. Though clinically, often there are not many options.

Earlier, there was an outbreak of avian influenza and the first human death linked to it was reported. Zika cases have been reported in Kerala and now one in Maharashtra. What kind of zoonotic diseases scenario are we looking at?

We have to stay alert with good, strong diagnostic platforms. We can’t forget about avian flu. We could have another pandemic tomorrow. Vector-borne viruses are a huge risk with global warming though more controllable since one can more easily stop mosquitoes than aerosols. But there are other pandemic risks… like slow development of antibiotic resistance which could happen while we are looking elsewhere and then we have no more antibiotics….