The effectiveness of vaccination and booster vaccinations against new coronavirus infection in real practice

The pandemic caused by the new coronavirus disease (COVID-19) was the largest in the last century since the Spanish Flu. One of the important strategies in the fight against COVID-19 has been vaccination. Although the end of the pandemic was declared in May 2023, the question of how the epidemic situation will spread (seasonal waves, new disease or gradual disappearance) remains unclear due to the high variability of the pathogen, which determines and changes recommendations in further immunization tactics. Purpose of the study : to compare the clinical effectiveness of the first vaccination, as well as 1–3 revaccinations against a new coronavirus infection in people of different ages and health conditions. Research methods : clinical observation of 1159 people aged 19 to 92 years (74,8% women), assessing the frequency and severity of confirmed coronavirus infection before vaccination and for 2 years after vaccination in comparison with health status and age of those vaccinated; laboratory examination – examination of a nasopharyngeal smear using realtime PCR (Real-time PCR) for SARS-CoV-2; statistical data processing. Results: out of 1159 people, 255 people (22.0%) fell ill before vaccinations, of which 154 people (22.5%) were among 684 healthy people, and 101 out of 475 (21.2%) were among people with chronic pathology. It was found that before the introduction of vaccinations, people 40–59 years old were significantly more likely to get sick compared to the group 60 years old and older (30,4% and 18,3%, respectively, p=0,015). Since December 11, 2020, 1106 out of 1159 people have been vaccinated against the new coronavirus infection, of which with adenovector vaccines (1056 people) and based on other technological platforms (50 people). Revaccinations were carried out only with adenovector vaccine: 1 revaccination – 780, 2 revaccination – 249 and 3 revaccination – 35 persons. After vaccination, a significant decrease in the number of sick people was revealed in all groups: after primary vaccination, 129 (11,7%) vaccinated people got sick, after 1 revaccination 44 out of 780 (5,6%), after repeated revaccination 5 out of 284 (1,7%). In the group of people with chronic pathology, a significant decrease in morbidity was also noted after the first revaccination: out of 366 revaccinated people, 24 people (6,5%) fell ill and after repeated revaccination: 3 out of 159 (1.8%), compared with the primary vaccination complex, 61 out of 467 vaccinated (13,0%), (p<0,001). Conclusion : In the absence of vaccination, middle-aged people are the highest risk group for developing coronavirus infection. A significant decrease in the incidence of diseases with an increase in the number of vaccinations has been established. Thus, among 1106 people who received the primary vaccine complex, 129 (11,7%) fell ill; after the complex vaccination and the first revaccination – 44 out of 780 (5,6%), in the group who received 2 and 3 revaccinations, 5 out of 284 vaccinated people fell ill (1,7%) (Px2<0,001).