Currently there are about 165 different vaccines for COVID-19 being developed around the world. The main types of vaccines include vector, inactivated, nucleic acid-based (DNA and mRNA) and recombinant protein-based vaccines. Russian adenovirus vector-based vaccine was registered by the Russian Ministry of Health on August 11 and became the first registered COVID-19 vaccine on the market. The announcement created a so-called “Sputnik moment” for the global community.
“Vectors” are vehicles, which can induce a genetic material from another virus into a cell. The gene from adenovirus, which causes the infection, is removed while a gene with the code of a protein from another virus spike is inserted. This inserted element is safe for the body but still helps the immune system to react and produce antibodies, which protect us from the infection.
The technological platform of adenovirus-based vectors makes it easier and faster to create new vaccines through modifying the initial carrier vector with genetic material from new emerging viruses that helps to create new vaccines in relatively short time. Such vaccines provoke a strong response from a human immune system.
Human adenoviruses are considered as some of the easiest to engineer in this way and therefore they have become very popular as vectors.
After the start of the COVID-19 pandemic Russian researchers extracted a fragment of genetic material from novel coronavirus SARS-COV-2, which codes information about the structure of the spike S-protein, which forms the virus’ “crown” and is responsible for connection with human cells. They inserted it into a familiar adenovirus vector for delivery into a human cell creating the world’s first COVID-19 vaccine.
In order to ensure lasting immunity Russian scientists came up with a breakthrough idea to use two different types of adenovirus vectors (rAd26 and rAd5) for the first and second vaccination, boosting the effect of the vaccine.
The use of human adenoviruses as vectors is safe because these viruses, which cause the common cold, are not novel and have been around for thousands of years.
Before the start of clinical trials the vaccine had gone through all stages of pre-clinical trials with experiments on different types of animals, including 2 types of primates.
Phase 1 and 2 clinical trials of the vaccine have been completed on August 1, 2020. All the volunteers are feeling well, no unforeseen or unwanted side effects were observed. The vaccine induced strong antibody and cellular immune response. Not a single participant of the current clinical trials got infected with COVID-19 after being administered with the vaccine. The high efficacy of the vaccine was confirmed by high precision tests for antibodies in the blood serum of volunteers (including an analysis for antibodies that neutralize the coronavirus), as well as the ability of the immune cells of the volunteers to activate in response to the spike S protein of the coronavirus, which indicates the formation of both antibody and cellular immune vaccine response.
Post-registration clinical trials involving more than 40,000 people in Russia will be launched in a week starting from August, 24. A number of countries, such as UAE, Saudi Arabia, Philippines and possibly India or Brazil will join the clinical trials of Sputnik V locally. The vaccine has received a registration certificate from the Russian Ministry of Health on August 11 and under emergency rules adopted during the COVID-19 pandemic can be used to vaccinate the population in Russia. Mass production of the vaccine is expected to start in September 2020.
The unique substance of the Sputnik V and method of using it has a patent protection in Russia, obtained by Gamaleya National Research Institute of Epidemiology and Microbiology.
Sputnik V clinical trials
General publications on adenoviral vector-based vaccines
Burmistrova DA, Tillib SV, Shcheblyakov DV, et al. Genetic Passive Immunization with Adenoviral Vector Expressing Chimeric Nanobody-Fc Molecules as Therapy for Genital Infection Caused by Mycoplasma hominis. PLoS One. 2016
Shcherbinin DN, Esmagambetov IB, Noskov AN, et al. Protective Immune Response against Bacillus anthracis Induced by Intranasal Introduction of a Recombinant Adenovirus Expressing the Protective Antigen Fused to the Fc-fragment of IgG2a. Acta Naturae. 2014
Tutykhina IL, Sedova ES, Gribova IY, et al. Passive immunization with a recombinant adenovirus expressing an HA (H5)-specific single-domain antibody protects mice from lethal influenza infection. Antiviral Res. 2013;97(3):318-328. doi:10.1016/j.antiviral.2012.12.021
List of studies on adenovirus vaccinesList of clinical trials on vaccines that use mRNA