We analyzed temporal changes in the frequencies of the ptxA, prn, fim2, and fim3 alleles in Bordetella pertussis strains isolated from pertussis patients in Moscow, Russia, from 1948 to 2004. The three strains used for the whole-cell vaccine harbored the alleles ptxA2, ptxA4, prn1, fim2-1, and fim3A. Vaccine-type alleles of ptxA (ptxA2 and ptxA4) were characteristic for all prevaccination strains and for 96% of the strains isolated in the 1960s and 1970s. At the beginning of the 1970s, ptxA2 and ptxA4 were replaced by the ptxA1 allele. In the 1980s and to the present, strains with ptxA1 were predominant in the B. pertussis population. All prevaccination strains harbored the prn1 allele, which corresponds to the vaccine-type allele. In subsequent years, the proportion of strains with the prn1 allele decreased and the proportion of prn3 and prn2 strains increased. From 2002 to 2004 strains with prn2 or prn3 were predominant in the B. pertussis population. The vaccine-type alleles fim2-1 and fim3A were found in all prevaccination strains and in 92% of the strains isolated from 1960 to 1989. The fim2-2 and fim3B alleles were first observed at the beginning of the 1980s. In subsequent years, these strains became predominant. Together with waning immunity, the antigenic divergence between vaccine strains and clinical isolates observed in the Moscow area may explain the persistence of pertussis, despite the high rates of vaccine coverage. The results demonstrate that the selection of B. pertussis strains for vaccine manufacturing must be based on a thorough study of the B. pertussis population.

The SARS-CoV-2 pandemic, which came to Russia in March 2020, is accompanied by morbidity level changes and can be tracked using serological monitoring of a representative population sample from Federal Districts (FDs) and individual regions. In a longitudinal cohort study conducted in 26 model regions of Russia, distributed across all FDs, we investigated the distribution and cumulative proportions of individuals with antibodies (Abs) to the SARS-CoV-2 nucleocapsid antigen (Ag), in the period from June to December 2020, using a three-phase monitoring process. In addition, during the formation of the cohort of volunteers, the number of seropositive convalescents, persons who had contact with patients or COVID-19 convalescents, and the prevalence of asymptomatic forms of infection among seropositive volunteers were determined. According to a uniform methodology, 3 mL of blood was taken from the examined individuals, and plasma was separated, from which the presence of Abs to nucleocapsid Ag was determined on a Thermo Scientific Multiascan FC device using the “ELISA anti-SARS-CoV-2 IgG” reagent set (prod. Scientific Center for Applied Microbiology and Biotechnology), in accordance with the developer’s instructions. Volunteers (74,158) were surveyed and divided into seven age groups (1–17, 18–29, 30–39, 40–49, 59–59, 60–69, and 70+ years old), among whom 14,275 were identified as having antibodies to SARS-CoV-2. The average percent seropositive in Russia was 17.8% (IQR: 8.8–23.2). The largest proportion was found among children under 17 years old (21.6% (IQR: 13.1–31.7). In the remaining groups, seroprevalence ranged from 15.6% (IQR: 8–21.1) to 18.0% (IQR: 13.4–22.6). During monitoring, three (immune) response groups were found: (A) groups with a continuous increase in the proportion of seropositive; (B) those with a slow rate of increase in seroprevalence; and (C) those with a two-phase curve, wherein the initial increase was replaced by a decrease in the percentage of seropositive individuals. A significant correlation was revealed between the number of COVID-19 convalescents and contact persons, and between the number of contacts and healthy seropositive volunteers. Among the seropositive volunteers, more than 93.6% (IQR: 87.1–94.9) were asymptomatic. The results show that the COVID-19 pandemic is accompanied by an increase in seroprevalence, which may be important for the formation of herd immunity.

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