Vaccinated and never infected with Covid-19: Third dose can boost your immunity


A new study by the Indian Council of Medical Research and National Institute of Virology has made a strong case for the administration of a precautionary third dose of the Covid-19 vaccine to boost immunity. The recommendation is particularly for people who have been vaccinated but not infected with the coronavirus in the past two years.

The researchers associated with the study compared three groups of people – ‘naïve vaccinees’, that is those who have taken the vaccine but have not been infected with Covid; individuals who have recovered from Covid-19 and who had taken two doses of the vaccine; and finally, individuals with SARS-CoV-2 breakthrough infection, that is those who contracted the virus after taking both the jabs.

“Our study demonstrated lower IgG (Immunoglobulin, a type of antibody) and Nab (neutralizing antibody) response in naïve vaccinees than other groups. This emphasises the waning immune response in naïve vaccinees post second dose and warrants the administration of precautionary dose to boost immunity,” researchers associated with the study told The Indian Express.

The study published recently in the Journal of Infection has looked into the IgG and neutralizing antibody response in individuals vaccinated with two doses of Covishield vaccine against B.1, Delta, Beta and Omicron variants of the virus.

The neutralising antibody is responsible for defending cells from pathogens. They are produced by the body as part of its immune response and their production can be triggered by an infection or vaccination against an infection. Immunoglobulin, also known as antibodies, are essentially glycoprotein molecules produced by white blood cells. They act as a critical part of the immune response by specifically recognising and binding to bacteria or viruses and helping to destroy them.

“Despite the fact that vaccines are effective against severe SARS-CoV-2 infection, many breakthrough and re-infection cases were observed during the pandemic. The shifting paradigm would be mainly due to the reducing/waning immune responses post either natural infection or vaccinations, emergence of the new SARS-CoV-2 variant and its immune escape potential,” the researchers pointed out in the study.