While much headway has been made in the development of the COVID-19 vaccine, there are still many unanswered questions about eligibility, side effects, and if someone who has already had COVID-19 should be vaccinated at all. In this first part of our new COVID FAQ series, Dr. Sundeep Mishra tackles these questions.

Question: Should we give vaccine to those who have already suffered from COVID infection?

Answer: This is a challenging question right now. Since we don’t have the data, we have to answer it, and therefore no official guidance on it is available. We will have to go by logic till the data is available.

Why we should give the vaccination

After COVID infection, the immunity developed isn’t life-long, and it can wane with time; quickly in some and a bit more slowly in others. Administration of vaccine after COVID disease can confer additional immunity.

Even with most vaccines, at least 2 doses are required.

1. First, the vaccine dose generates a primary immune response against SARS-CoV-2 virus. However, the primary immune response is slow and weak as it takes days for the body to generate enough antibodies and T cells to eliminate the virus. However, the body generates long-lasting memory B and T cells that “remember” the SARS -CoV -2 virus, generating immune memory.
2. Second, the vaccine dose generates a secondary immune response. The secondary immune response is stronger and quicker than the primary immune response as memory B and T cells are rapidly activated. This results in higher antibody concentrations and T cell counts around the body to eliminate the virus more quickly, reducing the symptoms and severity of COVID-19 if there is infection. In addition, more memory B and T cells are produced after infection which strengthens memory of the SARS -CoV-2 virus.

Thus, prior COVID infection only helps boost immunity or ensures that complete immunity is developed by subsequent administration of vaccine.

Some virus for e.g. flu virus undergoes mutation and therefore requires to redevelop immunity against the fresh strain. With COVID, there is no data as yet, but this possibility has to be kept in mind.

There are well-documented cases of re-infection; 40 patients or so reported from India itself. These patients might have been protected from re-infection if they had been vaccinated after the first infection.

What about side-effects of the vaccine?

Again, there is no solid data on this just yet. Looking at the 2-dose vaccine protocol, there is reportedly no increase in side-effects after the 2nd dose of vaccine as yet. It is estimated that up to 10% of participants in the Pfizer and Moderna vaccine trials had had the virus (although they didn't directly recruit volunteers who were symptomatic or were known to have been previously infected) being either asymptomatic or with such mild symptoms that they went undetected. Fortunately, the vaccines were found safe in these populations. Thus, it seems that vaccination after COVID infection will also likely be safe.

For whom should the vaccine not be given?

There is a word of caution for "long-haulers" — COVID patients whose symptoms linger weeks and months after their diagnoses — they might be at certain risk if they receive the vaccination.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The author, Dr. Sundeep Mishra is a Professor of Cardiology.