A study by Vellore Christian Medical College found that the government is far less likely to allow mix-and-match Covid-19 vaccine for booster doses. Currently, a mixture of Covid-19 vaccines is not allowed in the country, meaning that the precautionary dose is the same vaccine for both first and second doses.
The study by the Christian Medical College (CMC) in Vellore, shows that the Covishield booster dose has shown 6 to 10 times higher antibody levels after initial vaccination with Covaxin. However, according to experts, if the inoculating booster dose is the same as that of the primary and secondary vaccines, then there is a chance of a higher immunity level when compared to that of booster dose with a mix of 2 vaccines.
When Covishield is used as a booster dose for a person with a mix of 2 different first and second vaccines, with proportion not equal, then there is a chance of low immunity level, said an expert privy to the data. Results were reviewed by the National Technical Advisory Group on Immunisation (NTAGI) in a meeting held last week, Winsley Rose, principal investigator of the study.
The point noted here in the study came after Hyderabad-based Biological E approached the Indian drug council seeking to have an emergency vaccine use apporval of Corbevax booster dose for those adults who have been given two doses of either Covishield or Covaxin.
The study was conducted on 416 subjects aged 18 to 80 who took the second jab at least six months ago. The sources said the result came on the basis of the immunogenicity of the vaccines. “The results showed a significant boost in immunogenicity in terms of neutralizing antibodies after 28 days when compared with placebo cohort in both Covishield and Covaxin arms. The safety profile of Corbevax was found similar to that of the earlier clinical trials,” the company noted.