Phase 2 trials of the Russian Corona vaccine, Sputnik-V, have reportedly shown encouraging results, but scientists say the vaccine’s effectiveness is yet to be proved. Early results of the trials showed immune response with every participant developing antibodies to fight the virus and none of them had any serious side effects.
The report published in the medical journal, The Lancet, said every participant developed antibodies to fight the virus and had no serious side effects.
"Encouraging" and "so far so good" are some of the reactions from scientists in the UK - but there is still, clearly, a long way to go.
Although the vaccine showed an antibody response in all participants in phase 2, this does not necessarily mean it would protect them from the virus. That still has not been established yet.
Russia licensed the vaccine for local use in August, the first country to do so and before research data had been published. Experts say the trials conducted in Russia were too small to prove effectiveness and safety.
But last month, President Vladimir Putin said the vaccine had passed all the required checks and that one of his own daughters had been given it. Moscow hailed the results to blunt criticism even as some Western experts raised concerns about the speed of Russia's work.
Two trials of the vaccine, named Sputnik-V, were conducted between June and July, The Lancet paper said. Each involved 38 healthy volunteers who were given a dose of the vaccine and then a booster vaccine three weeks later.
The participants - aged between 18 and 60 - were monitored for 42 days and all of them developed antibodies within three weeks. Among the most common side effects were headaches and joint pain.
The trials were open label and not randomised, meaning there was no placebo and the volunteers were aware they were receiving the vaccine.
"Large, long-term trials including a placebo comparison, and further monitoring are needed to establish the long-term safety and effectiveness of the vaccine for preventing Covid-19 infection," the report said.
A third phase of trials will involve 40,000 volunteers from "different age and risk groups," according to the paper.
The Russian vaccine uses adapted strains of the adenovirus, a virus that usually causes the common cold, to trigger an immune response.
Critics also point out that the vaccine appeared to be safe in healthy people between the age of 18 and 60 for 42 days, because that was how long the study lasted. There is nothing to prove it will work for older people and those with underlying health conditions.
Of the many vaccines currently being trialled around the world, some will work better than others in certain situations and in certain groups of people. So knowing exactly how well they work and for whom is important. These have to be answered and there should be more openness and transparency, say critics.