LONDON – A second COVID-19 vaccine has reported positive results in an interim phase III analysis, with Russia’s Sputnik V showing 92% efficacy.

The news comes two days after the first readout from a phase III COVID-19 vaccine trial reported 90% efficacy for Pfizer Inc. and Biontech SE’s BNT-162b2, increasing optimism that it is possible to develop a safe and effective vaccine against the coronavirus.

As with BNT-162b2, only headline data on Sputnik V are available as yet. The calculation of 92% efficacy for the two-shot human adenovirus-based vaccine is based on 20 confirmed cases of COVID-19 occurring in volunteers taking part in the placebo-controlled phase III trial.

Unlike the BNT-162b2 readout, which was based on volunteers who had received two doses, the interim analysis of Sputnik V was carried out on 16,000 volunteers 21 days after the first injection with the vaccine or placebo.

The data on BNT-162b2, an mRNA vaccine, also involved more cases of COVID-19 infection. Pfizer initially planned to do an interim analysis after 32 cases were confirmed, but in consultation with FDA that was increased and the results announced on Nov. 9 involved 94 confirmed infections.

“Despite these differences, the data are encouraging, and suggest [Sputnik V] is also effective, although the numbers are too small to be sure of this yet,” said Gillies O’Bryan-Tear, of the Faculty of Pharmaceutical Medicine in the U.K.

That the early efficacy results for BNT-162b2 and Sputnik V are consistent also is good news for other vaccines in development, said Paul Hunter, professor in medicine at the University of East Anglia, U.K. “If the first two very different vaccines are about 90% effective, then it does suggest that several effective vaccines will reach market in the coming months,” he said.

More than 36,000 of the 40,000 participants in the phase III trial of Sputnik V have now received both doses, with no unexpected adverse events to date.

Sputnik V was approved in Russia under an emergency use authorization on Aug. 11, allowing it to be given to health care workers and volunteers in other high risk groups. Monitoring of 10,000 people who received the vaccine by that route also shows an efficacy rate of more than 90%, according to a joint statement from the Gamaleya National Center of Epidemiology and Microbiology, where the vaccine was discovered, and the Russian Direct Investment Fund (RDIF), the sovereign wealth fund that is supporting development and commercialization of Sputnik V.

Alexander Gintsburg, director of the Gamaleya Center, said publication of data from what he described as a “post-registration” trial opens the way for mass vaccination in Russia in the coming weeks. “Thanks to the production scale-up at new manufacturing sites, Sputnik V vaccine will soon be available for a wide population,” said Gintsburg.

Participants in the phase III trial will be followed up for six months. There also are Sputnik phase III trials ongoing in Belarus, United Arab Emirates and Venezuela, while a phase II/III is taking place in India. A separate study is assessing safety and immunogenicity in the elderly.

There are orders for more than 1.2 billion doses of Sputnik V from over 50 countries, according to RDIF. Supplies for the global market will be manufactured by partners in India, Brazil, China and South Korea, with existing contracts enabling production of 500 million doses outside Russia annually.

RDIF said it is considering requests from other countries and companies, to further increase foreign production capacity. Sputnik V comes in a freeze-dried formulation, making for easier rollout of vaccination programs.

Human adenoviral vector platform

Conditional approval of Sputnik V on Aug. 11 was based on two then-unpublished, non-randomized phase I/II trials. That stirred controversy when Russian President Vladimir Putin announced the approval at a time no data were available for scrutiny.

The results, subsequently published in The Lancet on Sept. 4, showed all 40 participants in the phase II trials produced antibodies against the spike protein on the SARS-CoV-2 virus on day 42 of the trial. In addition, neutralizing antibody responses occurred in all 40.

Comparing the antibody responses from the vaccination and from natural infection, using plasma from 4,817 people who had recovered from mild or moderate COVID-19, the responses to vaccination appeared to be higher.

Sputnik V uses recombinant human adenovirus type 26 and recombinant human adenovirus type 5, both of which are engineered to express the spike protein. Use of two different adenoviruses is intended to ensure that if immunity develops to the first, the second booster shot remains effective.

RDIF points to the long history of safety and efficacy of human adenoviral vectored products, noting they have been tested in more than 250 clinical studies and that since 2015 more than 3,000 people have been vaccinated with Ebola and Middle East respiratory syndrome vaccines developed at the Gamaleya Center.

In comparison, the chimpanzee adenoviral vectors and the messenger RNA technology platforms underpinning other COVID-19 vaccines have far less data behind them. Meanwhile, other vaccines using human adenoviruses have not adopted the strategy of using two distinct vectors.

“More and more countries are recognizing the human adenoviral vector platform and plan to include these vaccines, as the most studied and known, in their respective national vaccine portfolio,” said Kirill Dmitriev, CEO of RDIF. “Vaccines should be above politics. The world needs a diversified portfolio of high-quality vaccines, with Sputnik V, based on the well-tested human adenoviral vector platform, being an important element of it.”