Prevalence and Dynamics of SARS-CoV-2 Antibodies in the Population of St. Petersburg, Russia.

BACKGROUND: The aim of the study was to assess the prevalence of seropositive status for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-IgA, -IgM, and -IgG; its dynamics in connection with restrictive measures during the coronavirus disease (COVID-19) pandemic; and the quantitative dynamics of antibody levels in the population of St. Petersburg, Russia. METHODS: From May to November 2020, a retrospective analysis of Saint Petersburg State University Hospital laboratory database was performed. The database included 158,283 test results of 87,067 patients for SARS-CoV-2 detection by polymerase chain reaction (PCR) and antibody detection of SARS-CoV-2-IgA, -IgM, and -IgG. The dynamics of antibody level was assessed using R v.3.6.3. RESULTS: The introduction of a universal lockdown was effective in containing the spread of COVID-19. The proportion of seropositive patients gradually decreased; approximately 50% of these patients remained seropositive for IgM after 3-4 weeks; for IgG, by follow-up week 22; and for IgA, by week 12. The maximum decrease in IgG and IgA was observed 3-4 months and 2 months after the detection of the seropositive status, respectively. CONCLUSIONS: The epidemiological study of post-infection immunity to COVID-19 demonstrates significant differences in the dynamics of IgA, IgM, and IgG seropositivity and in PCR test results over time, which is linked to the introduction of restrictive measures. Both the proportion of seropositive patients and the level of all antibodies decreased in terms of the dynamics, and only approximately half of these patients remained IgG-positive 6 months post-infection.

Patients receiving hemodialysis do not lose SARS-CoV-2 antibodies more rapidly than non-renal controls: a prospective cohort study.

BACKGROUND: Patients with end-stage kidney disease receiving maintenance hemodialysis (HD) are at increased risk for mortality after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) compared with the general population. However, it is currently unknown whether the long-term SARS-CoV-2 humoral and cellular immune responses in patients receiving HD are comparable to individuals with normal kidney function. METHOD: The prospective cohort study included 24 patients treated with maintenance HD and 27 non-renal controls with confirmed history of coronavirus disease (COVID-19). In all participants the levels of specific IgG were quantified at three timepoints: 10, 18, and 26 weeks from disease onset. In a subgroup of patients, specific T-cell responses were evaluated. RESULTS: The seropositivity rate declined in controls over time and was 85% and 70.4% at weeks 18 and 26, respectively. All HD patients remained seropositive over the study period. Seropositivity rate at week 26 was greater among patients receiving HD: RR = 1.4 [95%CI: 1.17-1.94] (reciprocal of RR = 0.7 [95% CI: 0.52-0.86]), p = 0.0064. In both groups, IgG levels decreased from week 10 to week 26, but antibodies vanished more rapidly in controls than in HD group (ANOVA p = 0.0012). The magnitude of T-cell response was significantly lower in controls than in HD patients at weeks 10 (p = 0.019) and 26 (p = 0.0098) after COVID-19 diagnosis, but not at week 18. CONCLUSION: Compared with non-renal adults, patients receiving HD maintain significant long-term humoral and cellular immune responses following natural COVID-19.