On the Issue of Evaluating the Effectiveness of Vaccination of Employees of Medical Organizations against COVID-19

Relevance. Active mass vaccination of the population against a new COVID-19 is being carried out on the territory of the Russian Federation, which is recognized as a priority strategy for the country's healthcare for the near and long-term periods. One of the main risk groups that are subject to priority vaccination is medical workers. Aims. To evaluate the effectiveness of vaccination of medical organizations ' employees against COVID-19 based on the results of a 6-month prospective follow-up. Materials and methods. The observation group consisted of 356 employees of a medical organization who were vaccinated against COVID-19 with the drug «Gam-Covid-Vac» from December 2020 to April 2021. The effectiveness of vaccination of employees was evaluated by the coefficient of IgG positivity to SARS-CoV-2 by solid-phase enzyme immunoassay 3 weeks after the first administration and 3–4 weeks after the second administration of the vaccine and then 1 time per month. Employees who were revaccinated after 5–6 months. After the initial vaccination, they were examined 10–14 days after the introduction of the first component «Gam-Covid-Vac». A total of 1921 serum samples were studied. A specific T-cell immune response was determined in two study participants without seroprotection after administration of two components of the «Gam-Covid-Vac» vaccine and eight employees with the elimination of IgG antibodies 4–5 months after vaccination using ELISPOT technology. In addition, 92 blood serum samples of 32 employees from the observation group were examined for specific antibodies to adenovirus by indirect enzyme immunoassay. From December 2020 to June 2021, the study participants were subjected to dynamic clinical observation, once a week they were examined by PCR to detect SARS-CoV-2 RNA in smears from the pharynx and nose (a total of 5696 samples).

Results. After the completed course of immunization, the formation of both a humoral (in 99.4% of cases) and cellular immune response (100% among the studied samples) was confirmed. In the next 6 months after vaccination, cases of coronavirus infection were registered in 4.8% of those vaccinated, including 1 person – in the first month after vaccination and 16 – 3–5 months after vaccination. In all cases, the disease occurred in the form of an acute respiratory infection of mild or moderate severity and was characterized by a shorter period of virus isolation compared to similar data on the persistence of the virus in unvaccinated patients (15 days in vaccinated compared to 22 days in unvaccinated). It was found that the presence of immunity to adenovirus infection during vaccination with the drug «Gam-Covid-Vac» did not affect the possibility of forming an immune response to COVID-19. In the group of persons re-vaccinated with the first component of «Gam-Covid-Vac» after 5–6 months. after the initial vaccination, an immune response was received during the follow-up period. 

Conclusion. Thus, according to the results of the study, a high immunological and epidemiological effectiveness of vaccination against COVID-19 with the drug «Gam-Covid-Vac» was established in a group of medical workers, and the effectiveness and safety of the administration of a booster dose of the vaccine after primary vaccination was also shown.

1. Shchelkanov M.Yu., Kolobukhina L.V., Burgasova O.A., Kruzhkova I.S., Maleev V.V. COVID-19: etiologiya, klinika, lechenie. Infektsiya i immunitet. 2020, 10(3):421–445. (In Russ.). doi: 10.15789/2220-7619- CEC-1473.

2. Briko N.I., Kagramanyan I.N., Nikiforov V.V., Suranova T.G., Chernyavskaya O.Р., Polezhaeva N.A. Pandemic COVID-19. Prevention Measures in the Russian Federation. Epidemiology and Vaccinal Prevention. 2020;19(2):4–12 (In Russ.). https://doi.org/10.31631/2073-3046-2020-19-2-4-12

3. The coronavirus. Online map of the spread of coronavirus infection [Electronic resource] Mode of access: https://coronavirus-monitor.ru/ (accessed 10.07.2021) (In Russ.).

4. The coronavirus. Online map of coronavirus infection. Statistics [Electronic resource] Mode of access: https://coronavirus-monitor.info/ (accessed 10.07.2021) (In Russ.).

5. Paces J, Strizova Z, Smrz D, et al. COVID-19 and the immune system. Physiol Res. 2020;69(3):379–388. doi: 10.33549/physiolres.934492

6. Juno JA, Tan HX, Lee WS, et al. Humoral and circulating follicular helper T cell responses in recovered patients with COVID-19. Nat Med. 2020;26(9):1428–1434. doi: 10.1038/s41591-020- 0995-0

7. Ghomi R., Asgari N., Hajiheydari A., Esteki R., Biyabanaki F., Nasirinasab F. The COVID-19 pandemic: a systematic review of the current evidence. Russian Journal of Infection and Immunity. 2020;10(4):655–663 (In Russ.). https://doi.org/10.15789/2220-7619-TCP-1508

8. Palamenghi L, Barello S, Boccia S, Graffigna G. Mistrust in biomedical research and vaccine hesitancy: the forefront challenge in the battle against COVID-19 in Italy. Eur J Epidemiol. 2020 Aug;35(8):785–788. doi: 10.1007/s10654-020-00675-8

9. Wang J, Lu X, Lai X, Lyu Y, Zhang H, Fenghuang Y, Jing R, Li L, Yu W, Fang H. The Changing Acceptance of COVID-19 Vaccination in Different Epidemic Phases in China: A Longitudinal Study. Vaccines (Basel). 2021 Feb 25;9(3):191. doi: 10.3390/vaccines9030191

10. Fisher KA, Bloomstone SJ, Walder J, Crawford S, Fouayzi H, Mazor KM. Attitudes Toward a Potential SARS-CoV-2 Vaccine : A Survey of U.S. Adults. Ann Intern Med. 2020 Dec 15;173(12):964– 973. doi: 10.7326/M20-3569.

11. Bendau A, Plag J, Petzold MB, Ströhle A. COVID-19 vaccine hesitancy and related fears and anxiety. Int Immunopharmacol. 2021 Apr 27;97:107724. doi: 10.1016/j.intimp.2021.107724.

12. Temporary methodological recommendations of the Ministry of Health of the Russian Federation «The procedure for vaccination of adults against COVID-19» (In Russ.).

13. Logunov DY, Dolzhikova IV, Zubkova OV, Tukhvatulin AI, Shcheblyakov DV, Dzharullaeva AS, et al. Safety and immunogenicity of an rAd26 and rAd5 vector-based heterologous prime- boost COVID-19 vaccine in two formulations: two open, non-randomised phase 1/2 studies from Russia. Lancet. 2020 Sep 26;396(10255):887–897. doi: 10.1016/S0140-6736(20)31866-3.

14. Logunov DY, Dolzhikova IV, Shcheblyakov DV, Tukhvatulin AI, Zubkova OV, Dzharullaeva AS, et al. Gam-COVID-Vac Vaccine Trial Group. Safety and efficacy of an rAd26 and rAd5 vec- tor-based heterologous prime-boost COVID-19 vaccine: an interim analysis of a randomised controlled phase 3 trial in Russia. Lancet. 2021;397(10275):671–681. doi: 10.1016/S0140-6736(21)00234-8.

15. Kharchenko E.P. Vaccines against Covid-19: the Comparative Estimates of Risks in Adenovirus Vectors. Epidemiology and Vaccinal Prevention. 2020;19(5):4–17 (In Russ.). https://doi. org/10.31631/2073-3046-2020-19-5-4-17

16. Ryzhikov A.B., Ryzhikov Е.А., Bogryantseva M.P., Usova S.V., Danilenko E.D., Nechaeva E.A., et al. A single blind, placebo-controlled randomized study of the safety, reactogenicity and immunogenicity of the «EpiVacCorona» Vaccine for the prevention of COVID-19, in volunteers aged 18–60 years (phase I–II). Russian Journal of Infection and Immunity. 2021;11(2):283– 296 (In Russ.). https://doi.org/10.15789/2220-7619-ASB-1699

17. Platonova T.A., Golubkova A.A., Smirnova S.S. COVID-19 in the employees of healthcare facilities: characteristics of clinical manifestations in the acute and convalescence periods.

18. Epidemiоlоgy and infectious diseases. Current items 2021;11(4):25–30 (In Russ.). DOI: 10.18565/epidem.2021.11.4.25-30.