The first report on the Russian coronavirus vaccine, named Sputnik-V, says early tests showed signs of an immune response.
The report published by medical journal The Lancet said every participant developed antibodies to fight the virus and had no serious side effects.
Russia licensed the vaccine for local use in August, the first country to do so and before data had been published.
However, experts say the trials were too small to prove effectiveness and safety.
But Moscow has hailed the results as an answer to critics. Some Western experts have raised concerns about the speed of Russia’s work, suggesting that researchers might be cutting corners.
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.
Two trials 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 randomized, meaning there was no placebo and the volunteers were aware they were receiving the vaccine.
According to the report: “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.”
A third phase of trials will involve 40,000 volunteers from “different age and risk groups,” according to the paper.
Russia’s vaccine uses adapted strains of the adenovirus, a virus that usually causes the common cold, to trigger an immune response.
Kirill Dmitriev, head of a Russian investment fund behind the vaccine, said during a news conference that the report was “a powerful response to the skeptics who unreasonably criticized the Russian vaccine”.
He said that 3,000 people had already been recruited for the next phase of trials.
Health Minister Mikhail Murashko said Russia would start vaccinations from November or December, with a focus on high-risk groups.
However, experts warned that there was still a long way to go until a vaccine could enter the market.
According to the WHO, there are 176 potential vaccines currently being developed worldwide. Of those, 34 are currently being tested on people. Among those, eight are at stage three, the most advanced.