Inferring the true number of SARS-CoV-2 infections in Japan.

INTRODUCTION: In Japan, as of December 31, 2021, more than 1.73 million laboratory-confirmed cases have been reported. However, the actual number of infections is likely to be under-ascertained due to the epidemiological characteristics such as mild and subclinical infections and limited testing availability in the early days of the pandemic. In this study, we infer the true number of infections in Japan between January 16, 2020, and December 31, 2021, using a statistical modelling framework that combines data on reported cases and fatalities. METHODS: We used reported COVID-19 deaths and age-specific infection fatality ratios (IFR) to impute the true number of infections. Estimates of IFR were informed from published studies and were adjusted to reflect the effects of pharmaceutical interventions, mass vaccination, and evolving variants. To account for the uncertainty in IFR, we sampled values from relevant distributions. RESULTS: We estimated that as of December 31, 2021, 3.07 million (CrI: 2.05-4.24 million) people had been infected in Japan, which is 1.77 times higher than the 1.73 million reported cases. Our meta-analysis confirmed that these findings were consistent with the intermittent seroprevalence studies conducted in Japan. CONCLUSIONS: We have estimated that a substantial number of COVID-19 infections in Japan were unreported, particularly in adults. Our approach provides a more realistic assessment of the true underlying burden of COVID-19. The results of this study can be used as fundamental components to strengthen population health control and surveillance measures.

COVID-19 postacute care major organ damage: a systematic review.

BACKGROUND: Major organ complications have been reported in patients hospitalised for COVID-19; most studies lacked controls. OBJECTIVE: Examine major organ damage postdischarge among adults hospitalised for COVID-19 versus non-COVID-19 controls. DATA SOURCES: MEDLINE, Embase and Cochrane Library from 1 January 2020 to 19 May 2021. STUDY ELIGIBILITY CRITERIA: English language studies of adults discharged from hospital for COVID-19; reporting major organ damage. Single review of abstracts; independent dual review of full text. STUDY APPRAISAL AND SYNTHESIS METHODS: Study quality was assessed using the Joanna Briggs Institute Appraisal Checklist for Cohort Studies. Outcome data were not pooled due to heterogeneity in populations, study designs and outcome assessment methods; findings are narratively synthesised. RESULTS: Of 124 studies in a full evidence report, 9 included non-COVID controls and are described here. Four of the nine (three USA, one UK) used large administrative databases. Four of the remaining five studies enrolled <600 COVID-19 patients. Mean or median age ranged from 49 to 70 years with 46%-94% male and 48%-78% White race; 10%-40% had been in intensive care units. Follow-up ranged from 4 weeks to 22 weeks postdischarge. Four used hospitalised controls, three non-hospitalised controls and two were unclear. Studies used various definitions of, and methods to assess, major organ damage outcomes. While the magnitude of effect differed across studies, incident cardiac, pulmonary, liver, acute and chronic kidney, stroke, diabetes, and coagulation disorders were consistently greater in adults hospitalised for COVID-19 compared with non-COVID-19 controls. LIMITATIONS: Applicability to subgroups (age, gender, COVID-19 severity, treatment, vaccination status) and non-hospitalised patients is unknown. CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS: Postacute COVID-19 major organ damage is common and likely higher than controls. However, there is substantial uncertainty. More consistent reporting of clinical outcomes and pre-COVID health status along with careful selection of control groups are needed to address evidence gaps. PROSPERO REGISTRATION NUMBER: CRD42020204788.