Preliminary findings published in The Lancet report that Russia's Sputnik V vaccine has a 91.6 percent efficacy and is well-tolerated in its phase 3 trial, adding to the growing list of effective vaccines against SARS-CoV-2, the coronavirus responsible for COVID-19.

Sputnik V was at the center of some controversy last summer when the Russian government approved the vaccine based on just two months of testing. However, phase 3 trials indicate that efficacy is high. The clinical trial saw 19,866 people receiving two doses of either the vaccine (75 percent of them) or placebo (the rest). The vaccine uses a modified adenovirus, like the Oxford and Jensen vaccines, sporting the same spike protein used by SARS-CoV-2 to enter an organism.

Unlike the Oxford vaccine, Sputnik V uses different adenoviruses between the first and second doses. This approach is known as a “heterologous prime-boost.”  What they do have in common is the spike protein. This primes our immune system in recognizing that as the crucial target to focus on.  

“The vaccine trial results are coming thick and fast as high infection rates in areas where phase 3 clinical trials provide increasing amounts of data that together encourages us to believe that vaccines will soon be able to drive down the human cost of COVID-19," Dr Alexander Edwards, associate professor in biomedical technology at the University of Reading., UK, who was not involved in the study, said. "The more trial data we have, the better placed we are to understand how to make and use vaccines, so these results are welcomed.”

While the results are exciting there are some caveats. The participants were not all tested for COVID-19 across the duration of the trial, so the efficacy analysis only included symptomatic cases. It is welcome news that efficacy is so high for symptomatic cases, but it is possible that it may be different for people that didn’t show any symptoms. This has implications on transmission, as asymptomatic people can still spread the virus.

Unlike mRNA-based vaccines such as the Moderna and the Pfizer/BioNTech, Sputnik V is relatively inexpensive to produce and easy to store. It has already been ordered by several countries with India having agreed to manufacture 100 million doses.   

“These viral vaccines are relatively stable (no need for storage at extreme temperature), but do have to be ‘grown’ in bioreactors so we can expect a major expansion of the global capacity for manufacturing these adenovirus medicines," Dr Edwards added. "Manufacturing may remain a bottleneck for months to come, so the more vaccines available, the better for global health. Pandemic means “all”, and the only way to address a global problem is with a global response – sharing data, science, technology, and medicines.”

For more information about COVID-19, check out the IFLScience COVID-19 hub where you can follow the current state of the pandemic, the progress of vaccine development, and further insights into the disease.