Estimating pertussis incidence in general practice using a large Australian primary care database. Issue 30 (5th July 2021)

• Record Type: Journal Article
• Authors: Leong, Robert Neil F.; Wood, James G; Liu, Bette; Menzies, Robert; Newall, Anthony T.
• Is Part Of: Vaccine. Volume 39:Issue 30(2021)
• Page Start: 4153
• Page End: 4159
• Publication Date: 2021-07-05
• Subjects: Pertussis -- General practice -- Incidence -- Healthcare-seeking -- Underestimation; Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2021.05.079
• Languages: English
• ISSNs: 0264-410X

Abstract

Abstract: Background: While pertussis is notifiable in most countries, notifications typically underestimate the true pertussis burden. We explored the incidence of pertussis in general practice in Australia. Methods: Using MedicineInsight, a large longitudinal electronic medical record database of general practice (primary care) encounters which includes >1.5 million patients, we first defined a cohort of active patients and then used free-text search algorithms to identify patients with pertussis-related encounters. We defined and identified pertussis-related encounters in four patient categories: pertussis-associated (category 1), potential pertussis (category 2), epidemiologically-linked pertussis (category 3), and symptoms consistent with pertussis (category 4). Incident pertussis-related encounter rates per 100, 000 active patients were calculated from Jan 2008 to Aug 2015. Results: Estimated mean annual pertussis incidence increased as definitions were expanded, from 94.3 (category 1 patients only) to 148.8 (categories 1+2+3 patients combined) per 100, 000 active patients per year. Monthly time-series corresponding to the first three categories were highly correlated (Pearson's r > 90% for each pair), but each was poorly correlated with category 4. For categories 1+2+3, the highest incidence was among 0–4 and 5–9 year olds. Incidence was 30% higher in females than males (i.e. 184.5 vs 139.8 per 100, 00 active patients for categories 1–3 patients combined). Pertussis-associated incidence (category 1) was similar to national pertussis notification rates. Categories 2 and 3 added 25% and 33%, respectively, on average relative to category 1 incidence. The estimated incidence from categories 1+2+3 together were on average 64% higher than national pertussis notification rates. Conclusion: We provide comprehensive estimates of pertussis-related incidence in general practice (primary care), well in excess of notified pertussis incidence in Australia. This highlights the utility of MedicineInsight data in providing a greater understanding of the burden of medically-attended pertussis infections.