Russia’s Sputnik V COVID-19 Vaccine Deals Double Blow to Coronavirus in Phase 1 and 2 Clinical Trials

The Sputnik V COVID-19 vaccine comprises two components based on two different strains of adenovirus, rAd26-S and rAd5-S. Russian scientists have weakened the pathogens and modified their genomes to enable them to deliver the coronavirus RNA fragments to human cells, forcing them to generate large quantity of its membrane proteins. These molecules infiltrate immune cells and make them produce antibodies to the SARS-CoV-2 virus.

Preliminary results of the first two phases of clinical trials of two different variants of the Sputnik V COVID-19 vaccine published in the Lancet journal have now confirmed that both the vaccines stimulated the volunteers’ immune system to develop antibodies to SARS-CoV-2 and are safe for humans. According to the Russian news agency TASS, the volunteers were given injections of rAd26-S and rAd5-S cultures which were stored in a frozen form while others were administered a freeze-dried form of a vaccine. The volunteers received booster shots about five days after the first injection.

The scientists found that both adenoviruses and both vaccine formulations proved almost equally effective and caused all volunteers to develop antibodies to the coronavirus as well as taught T-cells to recognize this threat. The scientists believe that the booster dose significantly enhanced the effectiveness of the Sputnik V COVID-19 vaccine as only 60% of volunteers who received a single injection developed antibodies. Both adenoviruses and both vaccine formulations were also found to be equally safe for the volunteers who experienced only mild side effects, such as pain at the injection site or rise in body temperature, although no potentially life-threatening complications were observed over the 42-day trial period.

"To form a powerful immune response against SARS-CoV-2, it is important that a booster vaccination is provided. However, booster vaccinations that use the same adenovirus vector might not produce an effective response because the immune system may recognize and attack the vector. For our vaccine, we use two different adenovirus vectors in a bid to avoid the immune system becoming immune to the vector," one of the authors of the article, Deputy Research Director at the Gamaleya National Research Center for Epidemiology and Microbiology Denis Logunov said.

"These data collectively show that the heterologous vaccine based on rAd26-S and rAd5-S is safe, well tolerated, and does not cause serious adverse events in healthy adult volunteers. The vaccine is highly immunogenic and induces strong humoral and cellular immune responses in 100% of healthy adult volunteers, with antibody titres in vaccinated participants higher than those in convalescent plasma," the researchers wrote.


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Gamalei Institute of Epidemiology and Microbiology