Epidemiology of public health important disease conditions in Western Australia

Abstract

This thesis contains four primary projects and evidence of additional experience gained during my field placement at the Western Australia (WA) Department of Health in 2022-2023.

Project 1: Epidemiology of long COVID in a highly vaccinated population during a SARS-CoV-2 Omicron wave. To investigate the risk of long COVID and its impacts, 22,744 people who tested positive to acute respiratory syndrome coronavirus 2 infection mid 2022 were invited to complete a survey at 90 days. Log-binomial regression was used to examine potential predictors of long COVID and its impacts. Of the 11,697 (51.4%) who completed the survey, 2,130 (18.2%) met the case definition for long COVID. Female sex, age 50-69 years, pre-existing health conditions, and fewer vaccine doses were predictors of long COVID. Among those with long COVID, nearly 40% had consulted a general practitioner in the prior month due to thier symptoms. Of those who were working/studying before their infection, 17.8% reported reducing hours/discontinuing.

Project 2: Outbreak investigation of Salmonella Saintpaul infection in Western Australia. The study involved patients with probable or confirmed Salmonella (S) Saintpaul infections with specimens collected 20 January to 03 March 2023 (n=85). A case-control study, matched on age group, was conducted recruiting two people with Campylobacter infection as controls for every case of S. Saintpaul. Conditional logistic regression was used to assess potential risk factors. Although a point source was not identified for this cluster of S. Saintpaul cases, two fresh food items were identified as high-risk foods.

Project 3: Risk of myocarditis associated with COVID-19 vaccination in Western Australia, 2021-2022. This study estimated the risk of myocarditis associated with COVID-19 vaccination. Using the WA Department of Health COVID Vaccination Linked Data Repository, it included all (n=1,777,916) WA residents aged 16+ who received their first vaccination between February and November 2021. Poisson regression was used to estimate relative rates (RR) of myocarditis in the risk period (within 14 days post vaccination) compared to the non-risk period (43 or more days), for first and second doses. During the follow-up period, 120 myocarditis cases were identified. The absolute risk of myocarditis was low, with incidence rates of 29.5 and 62.6 per 100,000 person-years for first and second doses, respectively, but vaccination was associated with an increased risk (RR=3.0 (95% CI, 1.3-6.7) and 10.1 (6.1-16.6) respectively).

Project 4: Evaluation of the Japanese Encephalitis Virus (JEV) surveillance system in Western Australia. This evaluation aimed to assess JEV surveillance system performance using a mixed-methods approach. Ten key stakeholders participated in semi-structured interviews. A thorough review of relevant documents was also undertaken. Thematic analysis was used to evaluate the overall performance of the system. Recommendations for enhancement include establishing advanced in-house detection capabilities, increasing clinician awareness, and ensuring the involvement of all relevant stakeholders.

Lessons from the field and teaching: The final chapters present my field and teaching experiences as well as conference presentations. My lessons from the field highlighted the significance of improving the quality of online surveys, illustrated by the long COVID survey I led in WA. With over 22,000 participants, the study details the comprehensive methodology, focusing on the design, implementation, and post-data collection phases. My teaching experience for first-year MAE scholars centred on arboviral outbreak investigation procedures, mainly aggregating data and interpretation of relative risk.

Overall, the evidence generated from my research and MAE experience will broaden the applied epidemiology knowledge base and inform public health decisions and actions that address a range of public health problems. Show more