Herd immunity might arrive before the vaccine: Guleria

There are two issues: One is immediate availability of vaccine to decrease and prevent the pandemic. So if a vaccine is available, if you are able to give it to the high risk group and those who have a higher chance of the infection as a priority, we would be immediately able to decrease the number of cases and also decrease the number of deaths. If the virus doesn’t mutate or does not cause changes that may need you to again vaccinate yourself, because you may get re-infection, then there will be less utilisation of the vaccine down the line.

One issue is how the virus changes and what is the chance of reinfection and if that is a big issue, then should we get ourselves vaccinated to prevent the reinfection. We are learning how the virus behaves over the next few months and based on that there will be a decision on how frequently the vaccine is required. If we have good herd immunity whether it is required or not, this is a big challenge because a lot of money gets invested in vaccine doses and manufacturing and sometimes the vaccine industry is very concerned they may have a drop in the demand.

Most of the previous viral infection we had, has been due to other viruses like influenza. Coronavirus, we have almost seven other viruses in subsets in this coronavirus family. Four of them just cause flu-like symptoms, which are very mild. The other three we have, one was SARS, which was controlled and did not lead into a pandemic. We also have MERS coronavirus, which is not that infectious, so we have small outbreaks. This is the first pandemic of this magnitude with coronavirus, the previous pandemic was with influenza virus. What we are realising with this coronavirus, which is a new virus, is that it has origins in bats. This virus, although causes respiratory tract infection, it also causes a systemic effect. The virus attaches to receptors which are present in many organs in the body, the ACE2 receptor. It causes swelling of the blood vessels and if these blood vessels are in the heart, then it may cause myocardial damage to the muscles of the heart. It leads to higher chances of clotting and this leads to strokes. This virus can cause what we call long-Covid. Post Covid squeal, which is not anticipated to be serious, as most viral infections tend to recover and people have post-viral effects lasting for a few days, then they become alright.

There is controversial data as far as BCG is concerned. There is in-vitro data from labs, which suggests BCG vaccination does give some degree of immune response, which has an anti-viral effect also. One retrospective study from Israel did not show any benefit to people who had the BCG vaccine. But there is another study from Netherlands, which looked at people who are given the BCG vaccine five years ago for some other trial, and they found they had some degree of protection, as far as Covid-19 was concerned. Theoretically, it may be more beneficial, but we need more data, to say it is worthwhile to vaccinate all the elderly with BCG booster dose.