Herd immunity to SARS-COV-2 in the population of the Southern regions of the Far East of Russia

Russian-language publication activity of medical researchers in during the COVID-19 pandemic: “post-COVID-19 syndrome”

Aim. To study the dynamics and pattern of publications in Russian on post-COVID-19 syndrome (PCS) in order to assess the completeness of information and identify medical specialties with its most active investigation in Russia.

Material and methods. The search for publications was carried out in the database of the largest digital scientific library in Russia Elibrary.ru from February 1, 2021 to February 1, 2022. The study included publicly available medical publications on the consequences of coronavirus disease 2019 (COVID-19) in Russian. Publications were classified according to subject matter, study design, and evidence hierarchy. The data obtained is reflected using integers, percentages and graphs.

Results. The study included 478 publications, of which 196 (41%) presented data from original studies, while 269 (56,3%) reflected the results of existing sources. Expert community documents accounted for 2,7%. In terms of study design, most of original studies described case series (37,2%) and individual case reports (22,4%). Casecontrol studies accounted for 20,4%, cross-sectional studies — 8,7%, prospective cohort studies — 3,6%, randomized clinical trials — 1,5%, and systematic reviews — 1%. In addition, 5,1% of publications were devoted to preclinical studies, mathematical models and various methodological aspects. By topic, the largest number of publications noted cardiovascular (12,2%) and neurological manifestations of PCS (12,2%). Furthermore, 23,5% of publications described the course of PCS in specific groups of patients, particular issues of COVID-19 consequences, and healthcare management problems. We also revealed that 11,7% of publications were devoted to general rehabilitation, 71% — to imaging diagnostics, 5,6% — to herd immunity to the Severe Acute Respiratory Syndrome CoronaVirus 2 (SARSCoV-2), and 5,6% — to PCS features in children. The smallest number of publications considered mental (5,1%), gastroenterological (4,6%), pharmacological (4,6%), rheumatological (4%) and pulmonological aspects of PCS.

Conclusion. The dynamics and pattern of publications on COVID-19 in Russian are generally consistent with global trends and reflect the natural consequences of the pandemic. This analysis of publications on PCS showed that the most in-demand specializations in this filed are cardiology, neurology, and rehabilitation.

Longitudinal Randomized Cohort Study of SARS-CoV-2 Antibody Seroprevalence in the St. Petersburg Population

Introduction. Since the detection of the first COVID-19 patient, 2 years have passed, during which more than 287,862,000 people have fallen ill globally, of which about 1.9% died. The implementation of SARS-CoV-2 control programs required efforts from almost all countries. An important direction in the fight against COVID-19 has been the formation of herd immunity, the main tool for managing the pandemic. Study goal. The aim of the study was to assess the seroprevalence of antibodies (Abs) to SARS-CoV-2 nucleocapsid (Nc) and receptor binding domain (RBD) in the St. Petersburg population during the COVID-19 pandemic. Materials and methods. A longitudinal cohort randomized monitoring study of Ab seroprevalence (SARS-CoV-2 Nc, RBD) was organized and conducted according to a unified methodology developed by Rospotrebnadzor with the participation of the St. Petersburg Pasteur Institute. For this purpose, a cohort was formed of 1000 volunteers who participated in all five stages of seromonitoring. The cohort was divided into seven age groups: 1−17; 18−29; 30−39; 40−49; 50−59; 60−69; 70; and older (70+) years. Seropositivity levels (Nc, RBD) were assessed by quantitative and qualitative enzyme immunoassays. During the second year of monitoring, some volunteers were vaccinated with the GamCOVIDVac (84%) or EpiVacCorona (11.6%) vaccines approved in Russia. Statistical processing was carried out using Excel 2010. Confidence intervals for shares and percentages (95% CI) were calculated using the method of A. Wald and J. Wolfowitz with adjustment (A. Agresti, B.A. Coull). The statistical significance of differences was calculated by z-test, using the appropriate online calculator (p < 0.05) unless indicated. Results. There was a trend toward an increase in Nc seropositivity in stages 1−3 of seromonitoring, with a decrease in stages 4−5 among children and adults. The share of RBD seropositive steadily increased during all five stages of seromonitoring. The most frequent finding was low anti-RBD Abs levels (22.6−220 BAU/mL). High Ab levels were recorded statistically significantly less frequently. Asymptomatic forms were observed in 84−88% of SARS-CoV-2 seropositive volunteers. By the fifth stage of monitoring, this indicator significantly decreased to 69.8% (95% CI: 66.1−73.4). The monitoring revealed a statistically significant increase in anti-RBD Abs alongside a statistically significant decrease in the proportion of Nc seropositives. This dynamic was especially characteristic of persons vaccinated with GamCOVIDVac. Conclusion. Prior to the use of specific vaccines, a seroprevalence of anti-Nc Abs was noted. After the introduction of the GamCOVIDVac vaccine in adults, a decrease in the level of anti-Nc Abs was noted due to an increase in the proportion of RBD seropositive persons.