A study carried out by the Asian Institute of Gastroenterology (AIG) Hospitals in Hyderabad has said that a single dose of Covishield for those who have recovered from the infection is sufficient. The study, which has been published in the peer-reviewed International Journal of Infectious Diseases, revealed that those who have been previously infected with COVID-19 demonstrated a higher antibody response to a single dose of the Covishield vaccine compared to those who have not been previously infected.
As part of the study, 260 healthcare workers who were vaccinated between January 16 and February 5, 2021, were considered. The study’s goal was to evaluate each patient’s immunological memory response. Covishield vaccine was administered to all patients as part of the study. On analysing the observations from the research, doctors concluded that in comparison to those who had never been infected with COVID-19, the group that had been infected showed a higher antibody response to a single dose of the vaccine. Similarly, the Memory T-cell responses induced by a single dose of vaccine were higher in the case of those previously infected. Memory T cells are functionaries of the immune system, which attack specific organisms rather than general antigens and remain long-term even after infection.
The study noted that a single dose of vaccine given at three to six months after recovery from COVID-19 resulted in better results along with higher antibody responses. Thus, a single dose can be considered to be as effective as two doses of vaccine for those previously affected with COVID-19. Dr Nageshwar Reddy, Chairman, AIG Hospitals, who is also one of the study's co-authors, commented on the study's potential impact on overall vaccination administration strategy. Dr Reddy stated, “The results show that people who got infected with COVID-19 need not take two doses of vaccine yet as a single dose can develop robust antibody and memory cell response at par with two-doses for those who didn’t get the infection. This will significantly help at a time when there’s a shortage of vaccines in the country and more people can be covered using the saved doses.”
He added, “Once we attain the requisite number of people vaccinated for achieving herd immunity, these patients who got infected and received only one dose can take the second dose of the vaccine. At this point, all our strategies should be directed at the widespread distribution of available vaccines and to include the maximum number of people at least with a single dose."
However, many other experts strongly recommend taking two doses of the COVID-19 vaccines, as the second dose acts a booster shot, further strengthening the immunity system.
According to virologist Dr Shahid Jameel, a single dose will only give limited protection. Speaking to NDTV, he said that the suboptimal levels of antibodies will select for the variants that will evade antibodies. "If a person takes antibiotics for two days instead of the prescribed five-day course, the person is at the risk of developing antibiotic-resistant bacteria, which becomes harder to kill. Similarly, if you have good levels of antibodies, it will destroy the virus. If there are low levels of antibodies, some mutants may escape and become antibody-escape mutants,” he said, adding that a two-dose regime will provide better protection.
In a post on Facebook on June 12, Dr Padmanabha Shenoy, a rheumatologist in Kerala, said, "A single dose has only 33% protection against the Delta variant of the coronavirus. So full vaccination is the solution and we need to bring down the gap (between two doses) to six weeks."
(With Inputs)