The Indian Council of Medical Research (ICMR) has said that a study on mixing and matching of two COVID vaccines – Covaxin and Covishield – showed that combining these two COVID-19 vaccines elicited better immunogenicity than two doses of the same vaccine.
The study, by Pune-based National Institute of Virology (NIV), suggested that immunisation with combination of Covishield and Covaxin was safe and provides better immunity against COVID-19 variants.
“The findings suggested that immunisation 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,” the study said.
The study was conducted on 98 people, including 18 who had inadvertently received two doses of different vaccines in Uttar Pradesh.
“Though India so far has followed homologous approach (two doses of one vaccine) with Covishield and Covaxin, eighteen individuals, under the national program, inadvertently received Covishield as the first jab and Covaxin as the second,” it said.
The study titled ‘Serendipitous COVID-19 Vaccine-Mix in Uttar Pradesh, India: Safety and Immunogenicity Assessment of a Heterologous Regime’ has been uploaded on medRxiv, a preprint server and is yet to be peer reviewed.
“To the best of our knowledge, this is the first study which reports the effects of heterologous prime-boost vaccination with an adenovirus vectored vaccine followed by an inactivated whole virus vaccine,” the researchers said.
The researchers compared the safety and immunogenicity profile of those people who received two doses of different vaccines, against that of individuals receiving either Covishield or Covaxin.
The study showed that immunogenicity profile against Alpha, Beta and Delta variants in heterologous group was superior.
“We compared the safety and immunogenicity profile of them (18 individuals) against that of those receiving either Covishield or Covaxin. Lower and similar adverse events following immunisation in all three groups underlined the safety of the combination vaccine-regime.
“Immunogenicity profile against Alpha, Beta and Delta variants in the heterologous group was superior and IgG antibody and neutralising antibody response of the participants was also significantly higher compared to that in the homologous groups,” the study stated.
These findings have an important implication for the COVID-19 vaccination program wherein heterologous immunisation will pave the way for induction of improved and better protection against the variant strains of SARS-CoV-2, the researchers underlined
“Such mixed regimens will also help to overcome the challenges of shortfall of particular vaccines and remove hesitancy around vaccines in people’s mind that could have genesis in programmatic ‘errors’ especially in settings where multiple COVID-19 vaccines are being used,” they said.
Last month, an expert panel of India’s drug regulator, DCGI, recommended conducting a study on mixing doses of Covishield and Covaxin vaccines.
The recommendation came after the Christian Medical College (CMC) in Vellore sought permission to conduct such study.
The Subject Expert Committee of the Central Drugs Standard Control Organisation (CDSCO) said that purpose of this study is to assess whether a person can be given two different vaccine shots — one each of Covishield and Covaxin — to complete the vaccination course.
