Candidate COVID-19 vaccine Sputnik V has shown an interim efficacy of 91% based on analysing results from around 18,000 volunteers, some of whom got the actual vaccine and some who got a placebo, the Russian Direct Investment Fund (RDIF) said in a press statement on Tuesday.
The vaccine candidate is also being tested on human volunteers in India and will cost “less than $10 [₹700] for international markets”, the RDIF said in a statement.
Sputnik V has been developed by the Gamaleya National Research Center for Epidemiology and Microbiology and is being funded and promoted by the RDIF, Russia’s sovereign wealth fund.
The latest results, which are yet to be announced in a medical journal, were gleaned from ongoing double-blind, randomized, placebo-controlled Phase III clinical trials in Russia’s history involving 40,000 volunteers.
Of these, only 18,794 got both doses of the trial vaccine that are being administered 21 days apart. The analysis was done a week after the second days was administered.
According to the clinical trial protocol, there were three volunteers who got the vaccine for every one who got the placebo. Of the 14,095 who were inoculated with the actual vaccine, 8 later tested COVID-19 positive and of the smaller placebo group, of 4,699 nearly four times as many--31--tested positive. From this is derived the efficacy rate of 91%.
‘Efficacy’ rate
An ‘efficacy’ rate differs from vaccine ‘effectiveness’. The latter shows how protective a vaccine is when it is actually administered in the general population and efficacy--the number cited by pharmaceutical companies announcing trial results--only shows what fraction of those who got the vaccine tested positive versus compared to those who tested positive among those who got a placebo during the clinical trial phase. It is possible for a vaccine's effectiveness to be much lower than its efficacy.
The Oxford-AstraZeneca adenovirus-based vaccine candidate was reported on Monday to have an efficacy of 70% and Pfizer-BioNtech and Moderna's m-RNA vaccines reported efficacy rates in the low 90s. Like Sputnik V, these results are based on interim analyses from ongoing phase-3 trials.
The Russian vaccine used two different vectors based on the human adenovirus, which reportedly allows for a stronger and longer-term immune response as compared to vaccines using one and the same vector for two doses.