Criteria for Assessing the Epidemiological Situation of Pertussis in Russian Federation

Abstract

Relevance. Differences in case definition criteria and diagnostic recommendations of pertussis between different countries, pose challenges in the analysis and effective control of disease. An important component of successful surveillance is laboratory diagnostics, which, if used in a timely and quality manner, can influence the rate of reported cases. In addition, current criteria for epidemiological surveillance do not sufficiently take into account the severity of the disease and the vaccination status of the patient, which makes it difficult to take effective preventive measures. Aims. Assess the epidemiological situation regarding pertussis infection in Russia to propose criteria for epidemiological surveillance. Materials and methods. The data was obtained from official state statistics (form No. 2 «Information on infectious and parasitic diseases», No. 5 «Information on preventive vaccinations», No. 6 «Information on the contingents of children and adults vaccinated against infectious diseases») and analytical tables developed at G.N. Gabrichevsky Research Institute of Epidemiology and Microbiology, including information on each case of pertussis and collected from the Rospotrebnadzor Directorates in the Russian Federation (in 2017–2022). Statistical data processing and plotting were carried out with R version 4.1.2. Results. From 2002 to 2017, the incidence of pertussis in Russia did not exceed the established norms. However, in 2019 there was an increase in incidence. In 2023, the incidence of pertussis reached record levels over the past 22 years – 19.0 per 100 thousand population. Vaccination rates against pertussis have remained high since 2003. The structure of cases shows that the majority of pertussis cases occur among unvaccinated children in the first year of life; deaths from pertussis are recorded annually, mainly among unvaccinated children under 2 years of age. From 2017 to 2019, the incidence among the unvaccinated was significantly higher than among the vaccinated; in 2020-2022, incidence among the unvaccinated decreased, but remained higher than among the vaccinated during the period of COVID-19 restrictive measures. There was no statistically significant difference in the distribution of pertussis severity in the periods before and after the COVID19 pandemic. Outbreaks of infection are mostly without spread, and in 2020-2022 the proportion of such outbreaks has increased. Schools remain the main site of infection, but the proportion of cases in kindergartens has increased. Conclusions. The following criteria for epidemiological well-being are proposed: subject to the achievement of timely vaccination coverage in 95% of people of decreed ages and timely implementation of anti-epidemic measures, there should be no deaths from pertussis, the incidence of pertussis should be sporadic and registered predominantly (more than 50% of cases) in the form of mild forms, the majority of pertussis cases occur among unvaccinated children in the first year of life (no more than 30% of vaccinated cases) and outbreaks without the spread of infection should prevail (more than 50% of cases) over outbreaks with spread.