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Objectives: COVID-19 Omicron subvariants typically cause milder disease than previous strains, yet many patients were still admitted to hospital for acute care. We audited reasons for and details of admissions to identify opportunities to reduce hospitalisations. Methods: We reviewed all admitted patients who tested positive for SARS-CoV-2 from 1st December 2022 to 30th January 2023. Results: Of 600 patients with a positive COVID-19 polymerase chain reaction, 222(37%) were considered incidental diagnoses. Reasons for admission for symptomatic COVID-19 (375 patients, 63%) included worsening symptoms (226, 60%), exacerbation of comorbidities (89, 24%), and difficulty managing at home (38, 10%). Almost half were classified as a mild infection (175, 47%). Of the 231 patients aged over 70 years, only 55 (24%) had prior antiviral therapy, and 90 (39%) had 4+ vaccine doses. Patients speaking language other than English and having country of birth other than Australia were significantly associated with lower vaccination rates and not having antivirals prior to admission. Conclusions: One-third of COVID-19 hospital admissions were incidental, and half were for mild disease. Many patients had not received appropriate vaccination or antivirals in the community. Implications for public health: Improving uptake of vaccinations and antivirals, and increasing community support, with a focus on people from culturally and linguistically diverse backgrounds, may reduce the burden of COVID-19 on hospitals.

Abstract Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) community transmission was eliminated in Australia from 1/11/2020 to 30/6/2021, allowing evaluation of surveillance system performance in detecting novel outbreaks, including against variants of concern (VoCs). This paper aims to define system requirements for coronavirus disease 2019 (COVID-19) surveillance under future transmission and response scenarios, based on surveillance system performance to date. Methods This study described and evaluated surveillance systems and epidemiological characteristics of novel outbreaks based on publicly available data, and assessed surveillance system sensitivity and timeliness in outbreak detection. These findings were integrated with analysis of other critical COVID-19 public health measures to establish future COVID-19 management requirements. Results Twenty-five epidemiologically distinct outbreaks and five distinct clusters were identified in the study period, all linked through genomic sequencing to novel introductions from international travellers. Seventy percent (21/30) were detected through community testing of people with acute respiratory illness, and 30% (9/30) through quarantine screening. On average, 2.07% of the State population was tested in the week preceding detection for those identified through community surveillance. From 17/30 with publicly available data, the average time from seeding to detection was 4.9 days. One outbreak was preceded by unexpected positive wastewater results. Twenty of the 24 outbreaks in 2021 had publicly available sequencing data, all of which identified VoCs. A surveillance strategy for future VoCs similar to that used for detecting SARS-CoV-2 would require a 100–1000-fold increase in genomic sequencing capacity compared to the study period. Other essential requirements are maintaining outbreak response capacity and developing capacity to rapidly engineer, manufacture, and distribute variant vaccines at scale. Conclusions Australia’s surveillance systems performed well in detecting novel introduction of SARS-CoV-2 while community transmission was eliminated; introductions were infrequent and case numbers were low. Detection relied on quarantine screening and community surveillance in symptomatic members of the general population, supported by comprehensive genomic sequencing. Once vaccine coverage is maximised, future COVID-19 control should shift to detection of SARS-CoV-2 VoCs, requiring maintenance of surveillance systems and testing all international arrivals, alongside greatly increased genomic sequencing capacity. Effective government support of localised public health response mechanisms and engagement of all sectors of the community is crucial to current and future COVID-19 management.