Russian scientists presented preliminary results of the first two phases of clinical trials of two different forms of the Sputnik V vaccine on 76 volunteers which confirmed that both forms of the vaccine are safe for humans and stimulate their immune system to develop antibodies to SARS-CoV-2. The study results were published in the Lancet journal.
“These data collectively show that the heterologous vaccine based on rAd26-S and rAd5-S is safe, well tolerated, and does not cause serious adverse events in healthy adult volunteers. The vaccine is highly immunogenic and induces strong humoral and cellular immune responses in 100% of healthy adult volunteers, with antibody titres in vaccinated participants higher than those in convalescent plasma,” the researchers wrote.
On August 11, Russia became the first worldwide to register the vaccine against the coronavirus which was named Sputnik V. The preparation was developed by the Gamaleya National Research Center and passed clinical trials in June – July. It is based on a known platform previously used for other vaccines. On August 15, the Healthcare Ministry announced the production launch of the preparation. The third post-registration phase of clinical trials of the vaccine began on August 25.
Russian vaccine consists of two components based on two different strains of adenovirus, rAd26-S и rAd5-S.
The researchers weakened those pathogens and modified their genomes in such a way so that they deliver the coronavirus RNA fragments to human cells, forcing them to produce a large amount of its membrane proteins.
These molecules infiltrate immune cells making them produce antibodies to SARS-CoV-2.
Coronavirus dealt a double blow
“To form a powerful immune response against SARS-CoV-2, it is important that a booster vaccination is provided. However, booster vaccinations that use the same adenovirus vector might not produce an effective response because the immune system may recognize and attack the vector. <…> For our vaccine, we use two different adenovirus vectors in a bid to avoid the immune system becoming immune to the vector,” one of the authors of the article, Deputy Research Director at the Gamaleya National Research Center for Epidemiology and Microbiology Denis Logunov said.
According to the researchers, clinical trials of a vaccine were conducted using two different variants of Sputnik V.
Some volunteers received injections of rAd26-S and rAd5-S cultures which were stored in a frozen form and others were vaccinated with a freeze-dried form of a vaccine. The booster shots were administered approximately five days after the first injection. The frozen vaccine was tested at one of the branches of the Burdenko Military Hospital, while the freeze-dried one was tested in the clinic of the Sechenov University.
As subsequent observations demonstrated, both adenoviruses and both vaccine formulations were equally safe for the volunteers. They elicited a number of mild side effects, such as pain at injection site or elevated body temperature but over 42 days of trials the researchers have registered no potentially life-threatening complications.
Overall, both vaccine formulations turned out to be approximately equally effective causing all volunteers to develop antibodies to the coronavirus and teaching T-cells to recognize this threat. According to the scientists, the booster dose has elevated significantly the effectiveness of the Sputnik V vaccine, since after a single injection the antibodies were developed in only 60% of volunteers.
The researchers hope that the vaccine developed by them will be equally successful during larger-scale clinical trials approved on August 26. Over 40,000 volunteers of all age groups will participate in them.
Header: MOSCOW, RUSSIA – JULY 31, 2020: The first vaccine to prevent coronavirus infection is developed by the Gamaleya Federal Research Centre for Epidemiology. Gam-COVID-Vac is a viral vector two-component vaccine based on human adenovirus. Dmitry Kurakin/Health Ministry of the Russian Federation/TASS