Research published in The Lancet on Sept. 4 announced that patients involved in early tests of a Russian Covid-19 vaccine developed antibodies with "no serious adverse events".
However, experts are sceptical.
The trials conducted were too small to prove safety and effectiveness.
76 adults tested
Russian researchers reported on two small trials, each involving 38 healthy adults aged between 18 and 60.
They were given a two-part immunisation.
Each participant was given a dose of the first part of the vaccine and then given a booster with the second part 21 days later.
They were monitored over 42 days.
All developed antibodies within the first three weeks.
The report said the data showed that the vaccine was "safe, well tolerated, and does not cause serious adverse events in healthy adult volunteers".
Concerns raised
Despite the seemingly good news and quick development, Western scientists are palpably concerned over a lack of safety data.
The Russian trials, for one, did not use a placebo.
This meant that the participants knew they were receiving the vaccine and were not randomly assigned to different treatment groups.
Scientists would also be hard pressed to accept an experiment that is moved along so quickly, let alone one that was not randomised and without a placebo comparison.
Larger and longer trials would be needed to establish the long-term safety and effectiveness of the vaccine for preventing Covid-19 infection.
Russia denounced criticism
Russia, in response, denounced the criticism as an attempt to undermine Moscow's research.
The report said the 76 participants of these trials would be monitored up to 180 days.
It also said a more rigorous phase 3 clinical trial was planned with the involvement of 40,000 volunteers "from different age and risk groups".
Russia announced in August that its vaccine, named "Sputnik V", had already received approval.
"Sputnik V" is the Soviet-era satellite first launched into space in 1957.
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