Herd immunity may come before Covid vaccine goes off the shelf: Dr Guleria

New Delhi: AIIMS Director Randeep Guleria in an interview to IANS said we may reach a stage down the line where we may have a good amount of immunity, and the people may feel that there is now good immunity and the utility of the vaccine is not there.

He added, if the virus doesn't mutate or does not cause changes then people may not think to again vaccinate themselves and then, there will be less utilization of vaccine down the line.

Q: If a vaccine is available off the shelf by beginning of 2022 or end of 2021 for common people, wouldn't they have attained immunity against this viral infection, or maybe Covid-19 scenario improved by then. People may treat this viral infection like common cold and cough, which does not have an adverse health impact?

A: 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.

But, we may reach a stage down the line where we may have a good amount of immunity and the people feel there is now good immunity, the utility of the vaccine is not there. And, 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 utilization 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 that they may have a drop in the demand.

Q: You have mentioned about people having long-term side effects post their recovery from Covid-19 disease? If Covid-19 is from the coronavirus family, then why do patients develop medical complications that may have lasting health effects or prolonged illness?

A: 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 realizing with this coronavirus, which is a new virus, and is of the bat origin. This virus, although causes respiratory tract infection, but it does also cause 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 a serious problem, as most viral infections tend to recover and people have post-viral effects lasting for a few days then they become alright.