Moscow(CNN) Russia's sovereign wealth fund said on Wednesday that an early analysis of data from its Sputnik V coronavirus vaccine suggests it is 92% effective. However, some scientists are urging caution, noting that the data is far from conclusive.
The interim analysis of Sputnik V came after researchers identified 20 Covid-19 cases among Phase 3 trial participants who received the vaccine or a placebo, according to a news release from the Russian Direct Investment Fund (RDIF), which funded vaccine production and is responsible for selling it globally.
According to RDIF's news release, no unexpected adverse events have been identified during the Phase 3 trial. Some who received the Russian vaccine, which was developed by the Gamaleya Institute, had short-term minor adverse events such as pain at the injection site, flu-like syndrome including fever, weakness, fatigue and headache.
The Russian Phase 3 trial will continue for six more months and data from the trial will be published in an international medical journal following a peer review, RDIF said in a statement.
Separate from the ongoing Phase 3 trials, in September the vaccine was first administered to a group of volunteers from the "red zones" of Russian hospitals. Ten thousand vaccinated volunteers, including medics and other high-risk groups, were observed, RDIF said, and "confirmed the vaccine's efficacy rate of over 90%."
But Dr. Peter Hotez, an infectious disease specialist at Baylor College of Medicine who is also developing a coronavirus vaccine, told CNN he doubted that the 20 Covid-19 cases were enough to give a solid view of Sputnik V's efficacy.
"Intuitively, it doesn't make sense to claim 92% protection just based on 20 events. But we'll have to see the data," he said. "The regulators need to see the data and a regulatory authority that has experience should review the data such as the EMA, the European Medicines Agency. They're the ones that really need to look at this and say, well, you know, this is too small, really, for you to say is 92% effective."
RDIF's announcement followed an announcement by Pfizer and BioNTech on Monday that their Covid-19 vaccine was found to be more than 90% effective based on early analysis of its data. Their interim analysis followed more than 90 confirmed coronavirus cases among trial participants. More than 43,530 participants have been enrolled in the Phase 3 trial and 38,955 volunteers have received a second dose, Pfizer said Monday.
The two vaccines are different. Pfizer's is based on a messenger RNA platform, a never-before-approved vaccine technology, while RDIF's is based on an inactivated adenoviral vector. One advantage of adenoviral vaccines is that they do not need to be stored and transported in extremely cold temperatures, scientists say.
But Hotez cautions that no matter the vaccine make-up, drugmakers risk getting ahead of themselves by making efficacy claims at this point.
"I would say neither announcement should have been made. That's not how we do this. The way we do this is you submit the dossier to the regulators. The regulators authorize it, either authorize it or approve it. And then you go ahead, and you can release that information to the public with the clinical trial data ready to go," he added.
Martin McKee, professor of European public health at the London School of Hygiene and Tropical Medicine, told CNN that Pfizer initially planned an interim analysis on just 32 positive cases, but the FDA said it wasn't enough.
McKee agreed that 20 positive cases was a weak basis for analysis in Sputnik V's case, but nevertheless expressed "cautious optimism" about Russia's announcement. It all comes down to how many people are included in the trials, and the prevalence of infection in the communities where the trials are taking place, he said.
More than 20,000 people have received their first dose of the Sputnik V vaccine as part of the Phase 3 trial, and 16,000 participants have received the second dose, according to RDIF.
"I think [RDIF] know that they've got to get it vetted and they've said in the press release they will publish the leading international journals. So they're going to have to do that and those journals are not going to accept anything without fairly rigorous audits of the data. They are well aware of that, they have to not make any mistakes," McKee said.
RDIF told CNN that Russia will publish the clinical trial protocol for Sputnik V in November and the next interim analysis will be at 39 coronavirus cases.
Russia drew criticism from scientific circles earlier in the year, when it announced the world's first approved coronavirus vaccine for public use in August -- even before crucial Phase 3 trials had been completed.
Results from the first human tests of Sputnik V were published in The Lancet in September. Only 76 people were involved in the first two trials -- too few to determine if the Russian vaccine was safe and effective. But the peer-reviewed report said that only mild adverse effects were reported and the vaccine triggered an immune response in trial participants.
Eleanor Riley, professor of Immunology and infectious disease at the University of Edinburgh, has urged all vaccine makers to put quality and safety over speed.
RDIF's announcement of Sputnik V's interim analysis is "encouraging," she said in a statement to the UK's Science Media Centre. However, she added, "I worry that these data have been rushed out on the back of the Pfizer/BioNtech announcement earlier in the week."
"This is not a competition," she also said, voicing a concern of many in the scientific community.
"We need all trials to be a carried out to the highest possible standards and it is particularly important that the pre-set criteria for unblinding the trial data are adhered to avoid cherry picking the data. Anything less than this risks a public loss of trust in all vaccines, which would be a disaster."