NEW DELHI — Using a combination of two vaccines at the center of India’s national Covid-19 vaccination program has returned results of significantly higher safety and immunogenicity among subjects relative to other groups that were given two installments of the same dose, the Indian Council of Medical Research reported in a study.
“Immunogenicity profile against Alpha, Beta, and Delta variants in the heterologous group was superior; IgG [Immunoglobulin G] antibody and neutralizing antibody response of the participants was also significantly higher compared to that in the homologous groups.”
Four months into the program, events of mixed dosing raised considerable anxiety among the public with the potential to contributing to vaccine hesitancy. The biomedical research peak body conducted the current investigation against that backdrop.
In the study, the Indian Council of Medical Research—the apex body in India for the formulation, coordination, and promotion of biomedical research—compared the safety and immunogenicity profile of heterologous vaccination with those individuals who received either the indigenously-developed Covaxin or Covishield (AstraZeneca manufactured in India), and it showed better results.
In the study conducted in India’s northern state of Uttar Pradesh, individuals received Covishield as the first dose followed by inadvertent administration of Covaxin as the second dose at an interval of six weeks.
“It was like a natural experiment when (the) second time these individuals (were) inoculated with different doses inadvertently,” said Samiran Panda, Head of Epidemiology and Communicable Diseases at the Indian Council of Medical Research.
“We went to the place and collected samples of individuals.”
The research organization decided to conduct the study to alleviate anxiety and hesitancy related to the mixing of vaccines.
World Health Organization’s chief scientist Soumya Swaminathan had earlier warned against vaccines’ ill-informed combination, citing limited data on the subject.
A total of 18 participants were in the heterologous group in the Indian Council of Medical Research study. However, two participants were unwilling and were excluded. Among them, 11 were male, and seven were female, with a median age of 62 years.
“A comorbid condition [hypertension] was reported in one [5.5 percent] individual. In both the homologous groups, 40 individuals were included,” states the study.
“We compared the safety and immunogenicity profile of them against that of individuals receiving either Covishield or Covaxin (n=40 in each group). Lower and similar adverse events following immunization in all three groups underlined the safety of the combination vaccine regime.”
The study’s findings suggest that immunization with a combination of an adenovirus vector platform-based vaccine followed by an inactivated whole virus vaccine was not only safe but also elicited better immunogenicity.
“We did a comparison with the heterogeneous group and homologous group, we found better immune response,” said Panda.
“If somebody gets Covishield first and Covaxin second, it gives better immunity. This is the first study on a combination of Adenovector and whole variant vaccines.”
Sameer Bhati, a public health expert, said both Covaxin and Covishield are based on two different formulas, explaining how the combination of two vaccines works.
Covaxin contains the dead virus of Covid and instructs the immune system to develop a defense against the virus. However, Covishield is based on the virus vector formula where a weak virus of the common cold is used to develop immunity against the Covid virus.
“Although both vaccines tend to develop the immunity against the same virus, the mixing of (the) two vaccines may be beneficial for the public and may surely result in removing vaccine hesitancy and speed up the vaccination,” he said.
Yet, further detailed and in-depth research must be carried out on the limitations, as the study only surveyed 18 participants.
“For (the) implementation of the same at the national level, it must be analyzed more and in detail keeping in mind the variety of population,” Bhati said.
“Also, a detailed study on a follow-up period of 60 to 70 days is also required.”
(With inputs from ANI)
Edited by Saptak Datta and Krishna Kakani
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