Meanwhile, in India, the regulator has green-signalled conducting a study on combining the Covishield (AstraZeneca shot made by Serum Institute of India) and Covaxin (Bharat Biotech’s shot) by Christian Medical College (CMC), Vellore.
Experts feel that mixing of vaccines based on two different platforms could trigger a better immune response in the beneficiary. The mix and match approach, known as heterogeneous prime and boost, has been historically tried too, for example against Ebola.
When we take two doses of the same vaccine its called the homologous boost. Here the prime (first dose) and the boost (second dose) are the same vaccine. However, if two different vaccines that use the same antigen are used at prime and boost, it can show better immune response, feel some experts.
RDIF, AstraZeneca and R-Pharma announced preliminary results on immunogenicity (desired immune response triggered by a vaccine) of the combined use of AstraZeneca and Sputnik V vaccine doses. Azerbaijan had given the go-ahead to the world’s first clinical trials combining two Covid-19 vaccines in February.
The trial was run jointly by the Gamaleya Center, the lab which made the Sputnik V vaccine, alongside AstraZeneca, RDIF, and Russian pharmaceutical company R-Pharm.
Sputnik V is a heterogeneous vaccine. It uses two different human flu vectors (Ad26 and Ad5) in its two doses. The study used the first dose or the Ad26 vector based vaccine shot.
Clinical trials in Azerbaijan began in February 2021. To date 64 volunteers have been vaccinated, the enrollment of volunteers is ongoing.
“Preliminary data from the first 20 participants shows antibodies to the SARS-CoV-2 virus spike protein (S- protein) elicited in 100 per cent of cases,” RDIF said in a statement.
The interim analysis of data has previously demonstrated a high safety profile for the combined use of the vaccines with no serious adverse events or cases of coronavirus infection after vaccination, it added.
Clinical trials of a combination of vaccines are being carried out in several countries as part of a global program. Volunteers are being vaccinated in UAE and Argentina while regulatory approval to conduct trials has been granted in Russia and Belarus.