How long does immunity against COVID-19 last after vaccination? Does one need a booster dose?
Reports of health agencies in parts of the world considering a booster dose against fading immunity, particularly among the elderly, even after two doses of vaccine, has raised the uncomfortable question in India, which is struggling to vaccinate its vast population.
Though breakthrough infections – people testing positive for COVID-19 even after vaccination – have been reported in Karnataka, Dr. Mudassir Azeez Khan, Head of Community Medicine at Mysore Medical College and Research Institute (MMC&RI), in a presentation at a recent meeting of the newly constituted Mysuru District Technical Experts Committee on COVID-19, argued against the need for a booster dose.
“A breakthrough infection itself will act like a booster dose. A human body produces better antibody response against COVID-19 through natural infection than a third dose of vaccination,” he said.
Elaborating, Dr. Khan said SARS-COV-2, the virus strain causing COVID-19, has a total of 28 different proteins. “The antibodies generated from the vaccination will act only against the spike protein, which is on the surface. The remaining 27 proteins are not exposed to the antibodies generated from the vaccination. But, in the case of natural infection of COVID-19, all the 28 proteins will get exposed and the antibodies will fight the virus from all sides,” he said.
Dr. K.S. Satish, noted pulmonologist and member of State COVID-19 Expert Committee, also said studies have indicated that antibodies generated through natural infection, combined with vaccination, would give more lasting immunity. “Booster dose has been indicated only for those persons who are not expected to mount any antibody response because they are immuno-compromised. It is for people like cancer patients, who have undergone chemotherapy and have low immunity,” he explained.
Though immunity through vaccination is expected to last up to nine months as ‘we now know’, Dr. Satish said a lot of studies were under way to see if everyone requires a booster dose once a year, like the flu-shot in some countries. “We will know by the end of this year when the first batch of vaccine recipients (with both doses) are studied,” he said.
Dr. Khan pointed out that breakthrough infections, in most cases, are not life-threatening, and in a majority of instances do not even require hospitalisation.
Supporting the argument, Mysore Sanjeev, convenor of Project Jeevan Raksha, which is studying COVID-19 trends, pointed out that 93 of the 130 people hospitalised in Houston Medical Centre and Perry Hospital in the U.S. during August 2021 had not been vaccinated. “The Case Fatality Rate (CFR) in countries, which have fully vaccinated over 50% of their population, has come down sharply,” he said.
Dr. Khan recommends wider and swifter coverage of vaccination because the virus tends to mutate as it spreads among people. He attributed the emergence of Delta variant to the delay in vaccination in India.
Ruling out the possibility of a third wave in October, as predicted in some quarters, Dr. Khan said there is a possibility of some new variant emerging in the next six-seven months if vaccination coverage is not sufficiently expanded. “The possibility of a new variant emerging and sparking a fresh wave depends on the number of people yet to be vaccinated by March 2022,” he said.
