Association of vaccine-induced or hybrid immunity with COVID-19-related mortality during the Omicron wave -- a retrospective observational study in elderly Bavarians (preprint)

Background: There is a lack of population-based studies on the effectiveness and durability of the SARS-CoV-2-induced immune protection during the Omicron wave. Methods: This retrospective study included 470 159 cases aged 60 years or older, who tested positive for SARS-CoV-2 between January 1 and June 30, 2022 in Bavaria, Germany. We examined time to death, measured from the earliest date of reporting/symptom onset until day 60. Cox models were used to estimate adjusted hazard ratios (HR) for sex, age, earliest calendar date of documented infection, and level of vaccine-induced or hybrid immunity (LI). Results: We observed 3836 deaths (case fatality rate 0.82%). Risk of death was significantly lower in all LIs than in unvaccinated cases (adjusted HR for a full primary LI achieved within the last six months: 0.30, 95% confidence interval (CI) 0.23-0.39; after six months: 0.46, 95% CI 0.35-0.60). Boosting further decreased the risk of death (within the last three months: HR 0.17, 95% CI 0.15-0.20; after three months: HR 0.25, 95% CI 0.21-0.29). Conclusion: In elderly Bavarians, an increasing LI was associated with an increasing protection against death during the Omicron wave. Protection, however, may decrease to some extent after several months.

SARS-CoV-2 Antibodies in Children: A One-Year Seroprevalence Study From June 2020 to May 2021 in Germany (preprint)

Background: Investigating the role of children in the COVID-19 pandemic is pivotal to prevent the virus spreading. In most cases, children infected with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) develop non-specific symptoms or are asymptomatic. Therefore, the infection rate among this age group remains unclear. Seroprevalence studies, including clinical questionnaires, may contribute to our understanding of the time course and clinical manifestations of SARS-CoV-2 infections.Methods: SARS-CoV-2-KIDS is a longitudinal, hospital-based, multicentre study in Germany on the seroprevalence of anti-SARS-CoV-2 immunoglobulin G, as determined by an Enzyme-Linked Immunosorbent Assay in children (aged ≤17 years). A study-specific questionnaire provided additional information on clinical aspects.Findings: This analysis included 10,358 participants recruited from June 2020 to May 2021. The estimated anti-SARS-CoV-2 seroprevalence increased from 2·0% (95% confidence interval (95% CI) 1·6, 2·5) to 10·8% (95% CI 8·7, 12·9) in March 2021, without major change afterwards and was higher in children with migrant background (on average 6·6% vs. 2·8%). In the pandemic early stages, children under three years were 3·5 (95% CI 2·2, 5·6) times more likely to be seropositive than older children, with the levels equalising in later observations. History of self-reported respiratory tract infections or pneumonia was associated with seropositivity (OR 1·8 (95% CI 1·4, 2·3); 2·7 (95% CI 1·7, 4·1)).Interpretation: The majority of children in Germany do not have detectable SARS-CoV-2 IgG. To some extent, this may reflect the effect of differing containment measures implemented in the federal states. Detection levels might have been greater in certain age groups or migrant background. Lifting containment measurements is likely to cause a general increase in respiratory tract infections, which already pose a challenge to paediatric medical care during regular winter seasons. This challenge might become critical with additional infections caused by SARS-CoV-2.Funding: Funding Information: German Federal Ministry of Education and Research.Declaration of Interests: Authors have no conflicts of interest to declare.Ethics Approval Statement: Ethics committees of each study centre independently approved the study protocol. All parents/guardians gave written informed consent and children assented to the participation when appropriate for their age.

Is the BioNTech-Pfizer COVID-19 vaccination effective in elderly populations? Results from population data from Bavaria, Germany (preprint)

Background The effect of the BioNTech-Pfizer BNT162b2 vaccination in the elderly (≥80 years) could not be fully assessed in the BioNTech-Pfizer trial due to low numbers in this age group. We aimed to evaluate the effectiveness of the BioNTech-Pfizer (BNT162b2) vaccine to prevent SARS-CoV-2 infection and severe outcomes in octo- and novo-generians in a German state setting. Methods and Findings A prospective observational study of 708,187 persons aged ≥80 years living in Bavaria, Germany, was conducted between Jan 9 to Apr 11, 2021. We assessed the vaccine efficacy (VE) for two doses of the BNT162b2 vaccine with respect to SARS-CoV-2 infection and related hospitalisations and mortality. Additionally, differences in VE by age groups ≥80 to ≤89 years and ≥90 years were studied. Analyses were adjusted by sex. By the end of follow-up, 63.8% of the Bavarian population ≥80 years had received one dose, and 52.7% two doses, of the BNT162b2 vaccine. Two doses of the BNT162b2 vaccine lowered the proportion of SARS-CoV-2 infections and related outcomes, resulting in VE estimates of 68.3% (95% confidence interval (CI) 65.5%, 70.9%) for infection, 73.2% (95% CI 65.3%, 79.3%) for hospitalisation, and 80.1% (95% CI 80.0%, 89.0%) for mortality. Sex differences in the risk of COVID-19 outcomes observed among unvaccinated persons disappeared after two BNT162b2 vaccine doses. Overall, the BNT162b2 vaccine was equally efficacious in octo- and novo-genarians. Conclusions Two doses of BioNTech-Pfizer’s BNT162b2 vaccine is highly effective against COVID-19 outcomes in elderly persons.