According to an article published on Friday in The Lancet journal, Sputnik V, the world's first registered coronavirus vaccine, approved by Russia last month, has been shown to elicit antibody response with no serious adverse events in small human trials. The publication of the article carrying preliminary results of the Phase I-II clinical trials of the vaccine was announced by the Russian Direct Investment Fund (RDIF), Russia's sovereign wealth fund, and the Gamaleya National Research Center of Epidemiology and Microbiology of the Ministry of Health of the Russian Federation. The scientific publication in The Lancet proves the high safety and efficacy of the Russian vaccine and also provides detailed data on the results of the clinical trials. The article contains both the key qualitative and quantitative characteristics of the Sputnik V vaccine, favorably distinguishing it from other vaccines that are only just undergoing clinical trials in various countries and have no data on carcinogenicity or the effects on fertility. Results from early-phase non-randomized vaccine trials in a total of 76 people show that two formulations of the vaccine have a good safety profile detected over 42 days, and induce antibody responses in all participants within 21 days. Secondary outcomes from the trial suggest the vaccines also produce a T cell response within 28 days, the researchers said. The findings are based on two small phase trials lasting 42 days — one studying a frozen formulation of the vaccine, and another involving a lyophilized (freeze-dried) formulation of the vaccine, they said. The frozen formulation is envisaged for large-scale use in existing global supply chains for vaccines, while the freeze-dried formulation was developed for hard-to-reach regions as it is more stable and can be stored at 2-8 degrees Celsius, the researchers said. The two-part vaccine includes recombinant human adenovirus type 26 (rAd26-S) and recombinant human adenovirus type 5 (rAd5-S), which have been modified to express the SARS-CoV-2 spike protein. The adenoviruses, which usually cause the common cold, are also weakened so that they cannot replicate in human cells and cannot cause disease, according to the researchers. These vaccines aim to stimulate both arms of the immune system — antibody and T cell responses — so they attack the virus when it is circulating in the body, and also attack cells infected by SARS-CoV-2. "When adenovirus vaccines enter people's cells, they deliver the SARS-CoV-2 spike protein genetic code, which causes cells to produce the spike protein," said study lead author Denis Logunov, from Gamaleya National Research Center. "This helps teach the immune system to recognize and attack the SARS-CoV-2 virus. To form a powerful immune response against SARS-CoV-2, it is important that a booster vaccination is provided," Logunov said. However, Logunov said, booster vaccinations that use the same adenovirus vector might not produce an effective response. He said this is because the immune system may recognize and attack the vector, adding this would block the vaccine from entering people's cells and teaching the body to recognize and attack SARS-CoV-2. "For our vaccine, we use two different adenovirus vectors in a bid to avoid the immune system becoming immune to the vector," Logunov added. The trials took place in two hospitals in Russia, and were open-label and non-randomized, meaning that participants knew that they were receiving the vaccine and were not assigned by chance to different treatment groups. The trials involved healthy adults aged 18-60 years, who self-isolated as soon as they were registered, and remained in hospital for the first 28 days of the trial from when they were first vaccinated. In phase 1 of each trial, participants received one component of the two-part vaccine — four groups of nine participants were given the frozen or freeze-dried rAd26-S or rAd5-S component. In phase 2, which began no earlier than five days after the phase 1 trial began, participants received the full two-part vaccine — they received a prime vaccination with the rAd26-S component on day 0, followed by a booster vaccination with rAd5-S component on day 21. Both vaccine formulations were safe over the 42-day study period and well-tolerated, according to the study. The most common adverse events were pain at the injection site, hyperthermia, headache, asthenia (weakness or lack of energy), and muscle and joint pain. The authors note that these adverse effects are also seen with other vaccines, particularly those based on recombinant viral vectors. — Agencies
