BACKGROUND: PrEP has been government subsidised in Australia since April 2018 and actively promoted to community and doctors. We used national dispensing data for PrEP and antiretroviral therapy (ART) to evaluate the success of the national program.
METHODS: Using linked de-identified dispensing records of all government-subsidised PrEP, for each patient we calculated days covered or without PrEP (assuming daily dosing) and proportion of days covered (PDC) for the most recent 90 days. We examined rates and predictors of recent nonadherence/intermittent use (90-day PDC < 60%) and discontinuation (> 120 days without PrEP). We defined incident HIV infection as initiating ART > 60 days after initiating PrEP.
RESULTS: Uptake was rapid and sustained with 6,491 people initiating during the first quarter; declining to 3,403 in the most recent quarter. Over eighteen months 29,619 patients were dispensed 6,745,967 PrEP tablets; 98.7% were male and the median age was 35 years (IQR 28-45). Just above a quarter (25.9%) discontinued PrEP. The median 90-day PDC was 93.3% (IQR 67-100%). Independent predictors of 90-day PDC < 60% and/or discontinuation included female sex, younger age-group, patient and doctor non-inner-urban location, lower doctor PrEP-caseload, and more disadvantaged patients (see table).
The HIV incidence rate was 0.95/1000PY (24cases/25197PY) and was higher during PrEP gaps than days covered (1.66/1000PYs [14/8,443PYs] vs 0.60/1000PYs [10/16,754PYs], incident rate ratio 2.78, p=.007).

	n	90 day PDC < 60%	aOR	p	Discontinued	aOR	p
Total	29,618	20.1%			25.9%
Sex Male Female	29,241 (98.7%) 377 (1.27%)	20.9% 39.3%	ref 2.22	- <.001	25.5% 68.7%	ref 4.60	- <.001
Age group 18-29 30-39 40+	9,085 (30.7%) 9,899 (33.4%) 10,634 (35.9%)	25.0% 20.1% 18.8%	1.43 1.15 ref	<.001 .001 -	33.5% 24.8% 21.0%	1.77 1.32 ref	<.001 <.001 -
Patient location Inner Urban Other	15,292 (51.6%) 14,327 (48.4%)	19.2% 23.1%	ref 1.09	- .029	21.5% 31.1%	ref 1.13	- <.001
Doctor location Inner Urban Other	21,239 (71.7%) 8,380 (28.3)	19.3% 25.9%	ref 1.30	- <.001	21.5% 38.9%	ref 1.69	- <.001
Doctor PrEP caseload <=100 patients > 100 patients	13,741 (46.4%) 15,878 (53.6%)	24.9% 18.0%	1.52 ref	<.001 -	19.5% 34.9%	1.73 ref	<.001 -
Subsidy Routine Additional	26,506 (89.5%) 3,112 (10.5%)	20.6% 24.4%	ref 1.11	- .07	24.9% 35.2%	ref 1.32	- <.001

Table: Rates and predictors of 90-day PDC <60% or discontinuation.
CONCLUSIONS: Australia''s national government-subsidized PrEP program has scaled up rapidly. The high proportion of patients using less-than-daily-dosing may include appropriate intermittent PrEP. Uptake, adherence and discontinuation in women may reflect appropriate use under guidelines or the selective focus on promoting PrEP to gay and bisexual men. This study identified characteristics of patients and doctors to be targeted to improve retention/adherence and/or additional forms of HIV prevention.