NEW DELHI: Those who have got one dose of Covaxin after having contracted Covid infection before may have the same level of protection against the disease as those without prior infection but two doses of this Covid vaccine, a latest ICMR study has said.
Covaxin, a whole inactivated virus-based vaccine against coronavirus has been jointly developed by Bharat Biotech and ICMR.
In a pilot study conducted on 114 healthcare professionals, it has now been found that previous infection plus the first dose of Covaxin is equivalent to two doses of the vaccine in individuals who have not been infected by the virus.
For the research, blood samples were collected from 114 healthcare professionals and frontline workers who received Covaxin from February to May this year by scientists attached with ICMR’s National Institute for Research in Tuberculosis, National Institute of Epidemiology, Chennai, and the Division of Epidemiology & Communicable Diseases.
Of the individuals studied, 30 had a history of exposure to the virus while others did not.
Prior infection with SARS-CoV-2 was determined at baseline and serum samples were used to estimate SARS-CoV-2 nucleoprotein-specific IgG (IgG N), spike protein-specific (IgG S) and neutralizing antibodies (NAb).
Overall, good vaccine-induced antibody responses were seen in prior SARS-CoV-2–infected individuals, except in two, who received a single dose of Covaxin that was similar to antibody responses seen after a two-dose vaccination course administered to infection-naïve individuals.
“Our results in a varied group of healthcare professionals and frontline workers lend support to the previous studies (albeit mainly focused on mRNA vaccines) that increased levels of SARS-CoV-2 binding and neutralizing antibodies are present after a single vaccine dose in previously infected individuals and are comparable to the levels seen after two doses in those without prior infection,” the authors said.
Their paper also said that in conclusion, almost all participants with prior Covid infection, except two, had detectable antibodies at the time of vaccination.
The study offers evidence in support of public health-oriented and immunologically sustained vaccine strategies, the scientist noted.
They added that if these preliminary findings are confirmed in large population studies, a single dose of the Covaxin vaccine may be recommended to previously confirmed Covid infected individuals so that the naïve individuals could attain the larger benefit of a limited vaccine supply.