The number of confirmed COVID-19 cases worldwide amounted to 50 million at the beginning of November 2020. This is clearly not enough for the formation of herd immunity, which will prevent repeated outbreaks of the disease. Quarantine measures can only curb the spread of the disease to some extent, therefore specific preventive measures are needed to create collective immunity to COVID-19.The underlying principle of collective immunity is indirect protection of the whole of the population by immunising a certain part of it. Vaccination is the most effective approach to prevention of epidemic outbreaks. The aim of the study was to analyse promising approaches to the development of vaccines against novel coronavirus COVID-19 infection. The paper summarises data on development studies and clinical trials of COVID-19 vaccines conducted in different countries. It analyses the pros and cons of different platforms for vaccine development (attenuated vaccines, inactivated vaccines, subunit vaccines, DNA and RNA vaccines, recombinant vector vaccines). The paper presents a potential design of novel vaccines. It was concluded that COVID-19 vaccines might be developed both for immunising high-risk groups and for mass immunisation. An optimal solution for the second task would be to develop human or monkey adenovirus vector-based vaccines whose mass production has already been unveiled.

The pandemic of the new coronavirus (COVID-19) disease that began in December 2019 in China is still having a huge impact on all spheres of human life. The herd immunity, which is the most effective tool for preventing the spread of the disease, is formed in two ways: the passive way (i.e., the formation of a population not susceptible to re-infection due to the natural spread of the disease) and the active way (mass immunisation). High rates of COVID-19 vaccination were achieved thanks to the development and mass production of new vaccines. The selection of the most promising vaccine platforms is one of the key aspects of successful mass immunisation. The aim of the study was to compare the characteristics of COVID-19 vaccines used for mass immunisation. The paper analyses the vaccine technology platforms, efficacy of different types of vaccines based on clinical trial results, safety of vaccines for different population groups, and potential for scaling up vaccine production in order to ensure the necessary vaccination coverage. The vaccines currently used for mass immunisation are: BNT162b2 (Pfizer/BioNTech), mRNA1273 (Moderna), Gam-COVID-Vac (N.F. Gamaleya National Research Center for Epidemiology and Microbiology), Ad26.COV2.S (Johnson & Johnson), ChAdOx1-S (AZD1222) (AstraZeneca), BBIBP-CorV (Sinopharm), CoronaVac (Sinovac Biotech), and NVX-CoV2373 (Novavax). The comparison of the main characteristics of the vaccines demonstrated that the most promising types of vaccines for COVID-19 specific prophylaxis are RNA vaccines and recombinant adenovirus vector-based vaccines.

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The some epidemiologic characteristics of etiologic agent of disease, possible main and intermediate reservoirs of agent in the nature, mechanism of agents transmission, modern methods of diagnostics and identification of agent, perspective trends of elaboration of therapeutics for special prophylactic and current of diseases are viewed. The possibility of existing in no endemic regions outbreaks of MERS as the result of accidental acquire by persons, arrival from Middle East countries, determines of elaboration of complex effective epidemic measures.

Since the Dabie bandavirus (DBV; former SFTS virus, SFTSV) was identified, the epidemics of severe fever with thrombocytopenic syndrome (SFTS) caused by this virus have occurred in several countries in East Asia. The rapid increase in incidence indicates that this infectious agent has a pandemic potential and poses an imminent global public health threat.The analysis of molecular evolution of SFTS agent that includes its variants isolated in China, Japan and South Korea was performed in this review. The evolution rate of DBV and the estimated dates of existence of the common ancestor were ascertained, and the possibility of reassortation was demonstrated.The evolutionary rates of DBV genome segments were estimated to be 2.28 × 10-4 nucleotides/site/year for S-segment, 2.42 × 10-4 for M-segment, and 1.19 × 10-4 for L-segment. The positions of positive selection were detected in the viral genome.Phylogenetic analyses showed that virus may be divided into two clades, containing six different genotypes. The structures of phylogenetic trees for S-, M- and L-segments showed that all genotypes originate from the common ancestor.Data of sequence analysis suggest that DBV use several mechanisms to maintain the high level of its genetic diversity. Understanding the phylogenetic factors that determine the virus transmission is important for assessing the epidemiological characteristics of the disease and predicting its possible outbreaks.