Lucknow: As COVID-19 cases start to reappear in Uttar Pradesh and elsewhere, a recent study by King George’s Medical University (KGMU), published in the prestigious scientific journal Elsevier, has brought a reassuring message for those who have already received two doses of the COVID-19 vaccine.
The study concludes that individuals who have taken two vaccine doses have developed adequate immunity and do not require a third (booster) dose at this stage.
The research, conducted over six months from April to September 2023, involved a large sample of 7,643 residents from Lucknow and 10 surrounding districts. It was designed to examine the strength and longevity of immune responses among different population groups, including children, adolescents, and vaccinated adults.
The participants were tested for two types of immune responses — humoral and cellular antibodies. Out of the total participants, 643 individuals were tested for cellular antibodies, while 7,000 were evaluated for humoral antibodies. The presence and strength of these antibodies were used as indicators of the body’s defense against COVID-19.
In the group tested for cellular antibodies, a significant proportion included children aged between five and twelve and adolescents aged thirteen to seventeen. These individuals had not received any COVID-19 vaccine. The data revealed that the children displayed a comparatively lower level of antibodies, reaffirming the role of vaccines in boosting immune response. On the other hand, the adults who had taken both doses of the vaccine showed a markedly higher level of antibodies.
One of the most significant observations from the study was the comparison between those who had received two vaccine doses and those who had taken a third booster dose. It was found that while the antibody levels increased significantly after the second dose, the difference in immunity between the second and third doses was negligible.
“In other words, people who received only two doses had nearly the same level of protection as those who had taken a booster, indicating that the third dose did not significantly improve the body’s immune response,” said the study.
The researchers concluded that for most healthy individuals, two doses of the vaccine are sufficient to provide continued protection against the virus.
Another noteworthy finding of the study was that there was no significant difference in the antibody levels between people who had taken Covishield and those who had taken Covaxin. This suggests that both vaccines are equally effective in generating a strong immune response, and the type of vaccine administered made little difference in terms of immunity.
Dr. D. Himanshu, head of the Department of Infectious Diseases at KGMU, explained that the immune response to COVID-19 infection or vaccination involves two primary defence mechanisms — humoral and cellular immunity. Humoral immunity is based on B-cells, which produce antibodies that attach to the virus and neutralize it.
Cellular immunity, on the other hand, is carried out by T-cells, which identify and destroy infected cells and activate other immune responses. According to Dr. Himanshu, both these systems work together to offer robust and long-lasting protection against viral infections, including COVID-19.
The study was conducted by a multi-disciplinary team from KGMU, including Dr. Geeta Yadav, Dr. D. Himanshu, Dr. Hardeep Singh Malhotra, Dr. Amita Jain, Dr. Shruti Radera, Dr. Anil Kumar Verma, Dr. Shailendra Yadav, and Dr. Neeraj Kumar. Collaborating institutions included the Uttar Pradesh Health Department, with state surveillance officer Vikasendu Agrawal contributing to the data collection and analysis.
International inputs came from Dr. Ravi Prakash of the University of Manitoba in Canada, while experts from the Uttar Pradesh Technical Support Unit, including John Anthony, and Anuj Tripathi from the Directorate of Family Welfare and Health, were also part of the study team.
The findings come at a crucial time when concerns are rising about the re-emergence of COVID-19 in parts of India. However, this comprehensive study provides scientific reassurance that individuals who have already taken two doses of the vaccine remain well protected. For now, the evidence does not support the necessity of a third dose, especially in healthy individuals who are not in the high-risk category.
