Long COVID in a highly vaccinated but largely unexposed Australian population following the 2022 SARS-CoV-2 Omicron wave: a cross-sectional survey.

OBJECTIVE: To estimate the prevalence of long COVID among Western Australian adults, a highly vaccinated population whose first major exposure to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was during the 2022 Omicron wave, and to assess its impact on health service use and return to work or study. STUDY DESIGN: Follow-up survey (completed online or by telephone). SETTING, PARTICIPANTS: Adult Western Australians surveyed 90 days after positive SARS-CoV-2 test results (polymerase chain reaction or rapid antigen testing) during 16 July - 3 August 2022 who had consented to follow-up contact for research purposes. MAIN OUTCOME MEASURES: Proportion of respondents with long COVID (ie, reporting new or ongoing symptoms or health problems, 90 days after positive SARS-CoV-2 test result); proportion with long COVID who sought health care for long COVID-related symptoms two to three months after infection; proportion who reported not fully returning to previous work or study because of long COVID-related symptoms. RESULTS: Of the 70 876 adults with reported SARS-CoV-2 infections, 24 024 consented to contact (33.9%); after exclusions, 22 744 people were invited to complete the survey, of whom 11 697 (51.4%) provided complete responses. Our case definition for long COVID was satisfied by 2130 respondents (18.2%). The risk of long COVID was greater for women (v men: adjusted risk ratio [aRR], 1.5; 95% confidence interval [CI], 1.4-1.6) and for people aged 50-69 years (v 18-29 years: aRR, 1.6; 95% CI, 1.4-1.9) or with pre-existing health conditions (aRR, 1.5; 95% CI, 1.4-1.7), as well as for people who had received two or fewer COVID-19 vaccine doses (v four or more: aRR, 1.4; 95% CI, 1.2-1.8) or three doses (aRR, 1.3; 95% CI, 1.1-1.5). The symptoms most frequently reported by people with long COVID were fatigue (1504, 70.6%) and concentration difficulties (1267, 59.5%). In the month preceding the survey, 814 people had consulted general practitioners (38.2%) and 34 reported being hospitalised (1.6%) with long COVID. Of 1779 respondents with long COVID who had worked or studied before the infection, 318 reported reducing or discontinuing this activity (17.8%). CONCLUSION: Ninety days after infection with the Omicron SARS-CoV-2 variant, 18.2% of survey respondents reported symptoms consistent with long COVID, of whom 38.7% (7.1% of all survey respondents) sought health care for related health concerns two to three months after the acute infection.

SARS-CoV-2 Vaccine Effectiveness against Omicron Variant in Infection-Naive Population, Australia, 2022.

SARS-CoV-2 transmission in Western Australia, Australia, was negligible until a wave of Omicron variant infections emerged in February 2022, when >90% of adults had been vaccinated. This unique pandemic enabled assessment of SARS-CoV-2 vaccine effectiveness (VE) without potential interference from background immunity from prior infection. We matched 188,950 persons who had a positive PCR test result during February-May 2022 to negative controls by age, week of test, and other possible confounders. Overall, 3-dose VE was 42.0% against infection and 81.7% against hospitalization or death. A primary series of 2 viral-vectored vaccines followed by an mRNA booster provided significantly longer protection against infection >60 days after vaccination than a 3-dose series of mRNA vaccine. In a population free from non-vaccine-derived background immunity, vaccines against the ancestral spike protein were ≈80% effective for preventing serious outcomes from infection with the SARS-CoV-2 Omicron variant.

Travel-associated SARS-CoV-2 transmission documented with whole genome sequencing following a long-haul international flight.

BACKGROUND: Multiple instances of flight-associated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission during long-haul flights have been reported during the COVID-19 pandemic. However, comprehensive investigations of passenger risk behaviours, before, during and after the flight, are scarce. METHODS: To investigate suspected SARS-CoV-2 transmission during a flight from United Arab Emirates to Australia in July 2020, systematic, repeated polymerase chain reaction (PCR) testing of passengers in hotel quarantine was linked to whole genome sequencing. Epidemiological analyses of in-depth interviews covering behaviours during the flight and activities pre- and post-boarding were used to identify risk factors for infection. RESULTS: Seventeen of the 95 passengers from four different travel origins had PCR-confirmed infection yielding indistinguishable genomic sequences. Two of the 17 passengers were symptomatic within 2 days of the flight, and classified as co-primary cases. Seven secondary cases were seated within two rows of the co-primary cases, but five economy passengers seated further away and three business class passengers were also infected (attack rate = 16% [15/93]). In multivariable analysis, being seated within two rows of a primary case [odds ratio (OR) 7.16; 95% confidence interval (CI) 1.66-30.85] and spending more than an hour in the arrival airport (OR 4.96; 95% CI 1.04-23.60) were independent predictors of secondary infection, suggesting travel-associated SARS-CoV-2 transmission likely occurred both during and after the flight. Self-reported increased hand hygiene, frequent aisle walking and using the bathroom on the plane did not independently affect the risk of SARS-CoV-2 acquisition. CONCLUSIONS: This investigation identified substantial in-flight transmission among passengers seated both within and beyond two rows of the primary cases. Infection of passengers in separate cabin classes also suggests transmission occurred outside the cabin environment, likely at the arrival airport. Recognizing that transmission may occur pre- and post-boarding may inform contact tracing advice and improve efforts to prevent future travel-associated outbreaks.

Successful Control of an Onboard COVID-19 Outbreak Using the Cruise Ship as a Quarantine Facility, Western Australia, Australia.

Onboard quarantining has been only partially effective to control outbreaks of coronavirus disease on cruise ships. We describe the successful use of the ship as a quarantine facility during the response to the outbreak on the MS Artania, which docked in Western Australia, Australia. The health-led 14-day quarantine regime was based on established principles of outbreak management and experiences of coronavirus disease outbreaks on cruise ships elsewhere. The attack rate in the crew was 3.3% (28/832) before quarantine commencement and 4.8% (21/441) during quarantine on board. No crew members became symptomatic after completion of quarantine. Infection surveillance involved telephone correspondence, face-to-face visits, and testing for severe acute respiratory syndrome coronavirus 2. No serious health issues were reported, no response staff became infected, and only 1 quarantine breach occurred among crew. Onboard quarantine could offer financial and operational advantages in outbreak response and provide reassurance to the shore-based wider community regarding risk for infection.

Using data linkage to monitor COVID-19 vaccination: development of a vaccination linked data repository.

The COVID-19 Vaccination Linked Data Repository (CVLDR) was established in 2021 to assist with the implementation and management of the COVID-19 vaccination program in the State of Western Australia (WA). The CVLDR contains a number of datasets including the Australian Immunisation Register, hospital admissions, emergency department attendances, notifiable infectious disease, and laboratory data. Datasets in the CVLDR are linked using a probabilistic method at the WA Department of Health. Quality assurance mechanisms have been established to identify and mitigate potential errors in the linkage. Each of the datasets has varying degrees of data quality and completeness, however most are of high standard, underpinned by legislation. The linking of the datasets within the CVLDR has allowed for increased public health utility in the immunisation program including the areas of vaccine safety, effectiveness, and coverage.