India’s ‘warm’ vaccine candidate effective against Delta, Omicron variants in mice, study suggests

According to a study conducted on mice, a heat-stable Covid-19 vaccine being developed in India that does not require cold chain storage has induced a significant antibody response against coronavirus variations such as Delta and Omicron.

The vaccine candidate, developed by the Indian Institute of Science (IISc) in Bengaluru and biotech start-up Mynvax, makes advantage of the receptor-binding domain (RBD) of the viral spike protein, which allows the virus to interface with the host cell and infect it.

Most vaccinations require refrigeration to be effective, according to the team, which included experts from Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO). The heat-tolerant Covid-19 vaccine candidate can be kept at 37°C for four weeks and at 100°C for up to 90 minutes.

In comparison, the Oxford-AstraZeneca vaccination, called as Covishield in India, must be stored at temperatures ranging from 2 to 8 degrees Celsius, while the Pfizer preventative requires specialised cold storage at minus 70 degrees Celsius. The most recent study, published in the journal Viruses, looked at the efficiency of vaccinated mice sera (blood samples) against major coronavirus variations including Delta and Omicron.

The researchers discovered that mice immunised with various vaccine formulations produce high titres (units to quantify amount or concentration) of antibodies that neutralise SARS-CoV-2 variants VIC31 (reference strain), Delta, and Omicron coronaviruses.

In comparison to VIC31, one formulation of the Mynvax vaccine had a 14.4-fold reduction in neutralisation against the Omicron variant while another formulation had a 16.5-fold reduction. According to the study, the equivalent values for decrease in neutralisation against the Delta variation were 2.5 and 3.

”The average 14.4- or 16.5-fold reduction in neutralisation against Omicron BA.1.1 for the monomeric and trimeric formulations, respectively, compares favourably with equivalent reductions observed with leading Covid-19 vaccines,” the authors of the study noted.

Upcoming Phase I human clinical trials

“Our findings suggest that monomeric formulations are suitable for upcoming Phase I human clinical trials and that there is potential for increasing the efficacy with vaccine matching to improve the responses against emerging variants,” they wrote in the journal.

The terms monomeric and trimeric formulations relate to the many forms and combinations that can be utilised in the development of the vaccine. The CSIRO’s assessment of the various Mynvax formulations will aid in the selection of the best candidate and dose for planned human clinical studies in India.

The vaccine’s heat tolerance and capacity to tolerate transient thermal shocks are particularly promising for addressing the vaccination disparity that affects the majority of low- and lower-middle-income nations, according to the researchers. Over 10 billion Covid-19 vaccine doses have been delivered globally, with 51 nations reaching more than 70% of their population. However, in low-income nations, this figure is merely 11%.