Sputnik V, which the Kremlin announced in August would enter mass production this month despite serious international concern, caused no major adverse effects and induced antibodies in all participants in two small rounds of early testing. The results were published in medical journal The Lancet on Friday.
Experts not involved in the study said the findings were “encouraging but small” and did not yet prove the vaccine was effective or safe.
The Kremlin announced regulatory approval of Sputnik V on 11 August, making it the world’s first Covid-19 vaccine cleared for use, and said it planned to begin mass immunisation in September. But experts condemned Russia’s announcement as “unethical”, “reckless” and “foolish” as the vaccine has yet to be tested on a large scale in phase 3 clinical trials, considered essential to establish efficacy and safety.
Phase 3 testing of the vaccine, developed by Moscow’s Gamaleya Research Institute, began this week and will ultimately see 40,000 volunteers injected.
The trials covered in The Lancet study were phase 1 and 2, which involve smaller numbers of participants and aim to establish whether a drug works, if there are any side effects or safety concerns, and appropriate dosage levels.
A total of 76 volunteers took part in the two trials, which tested a frozen formulation of the vaccine planned for large-scale use in existing global supply chains and a freeze-dried version developed for remote regions. The vaccine induced an antibody response in all participants within 21 days and no serious adverse effects were detected over 42 days.
Sputnik V also appeared to trigger a T-cell response, which can help to provide long-term protection again the virus.
The vaccine is one of dozens in development around the world. A Covid-19 vaccine candidate developed by Oxford University researchers was found to induce a strong immune response and to be safe, according to results published in July of phase 1 and 2 trials involving 1,077 people.
The Russian trials, held at two hospitals in Russia, were open-label and not randomised, meaning participants knew they were receiving the vaccine and were not assigned by chance to different treatment groups.
Volunteers were healthy adults aged between 18 and 60 who self-isolated as soon as they were registered for the trial and remained in hospital for the first 28 days after vaccination.
Dr Ohid Yaqub, senior lecturer at the University of Sussex’s Science Policy Research Unit, said: “Normally, such a study would be the basis for debating whether to proceed into larger trials and the costs that entails. In that context, the study results are encouraging in terms of safety and possible efficacy.
“However, in the context of regulatory approval, the design and size of a phase 1 and 2 study is not anywhere near sufficient for widely recognised standards of approval. The study was not randomised, and it was not large enough to detect rarer safety issues.”
In an independent comment piece published by The Lancet alongside the study, Dr Naor Bar-Zeev of Baltimore’s International Vaccine Access Centre, said the trial results were ”encouraging but small”.
“The immunogenicity bodes well, although nothing can be inferred on immunogenicity in older age groups, and clinical efficacy for any Covid-19 vaccine has not yet been shown,” he wrote. “Safety outcomes up to now are reassuring, but studies to date are too small to address less common or rare serious adverse events.”
The Russian researchers acknowledged more tests was needed to needed to evaluate the vaccine in different populations, including older age groups and people with underlying medical conditions.
Professor Alexander Gintsburg, director of the Gamaleya Research Institute, claimed “unprecedented measures have been taken to develop a Covid-19 vaccine in Russia” and preliminary clinical studies had “made it possible to provisionally approve the vaccine”.
Russia’s health minister last week said that “first large batches” of the vaccine will be supplied this month, with healthcare workers and teachers invited to be first injected on an “absolutely voluntary” basis.
But international scientists warned the latest trial results did nothing to dispel concerns about fast-tracked roll-out of the jabs.
“At this stage, we do not know if the vaccine actually works – that is what the phase 3 trials will tell us,” said Dr Michael Head, senior research fellow in global health at University of Southampton.
“Public confidence in any licensed vaccine is vital, and suggestions from both Russia and the USA that a vaccine may be fast-tracked without the proper research having taken place are problematic. We must be open and transparent about the effectiveness and safety profiles of all vaccine candidates. Ultimately, we must not pour additional fuel on the anti-vaccine lobby fires.”
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