Association between COVID-19 vaccination rates and the Australian ‘Million Dollar Vax’ competition: an observational study

OBJECTIVE: To examine the association between financial incentives from entry into a vaccine competition with the probability of vaccination for COVID-19. DESIGN: A cross-sectional study with adjustment for covariates using logistic regression. SETTING: October and November 2021, Australia. PARTICIPANTS: 2375 respondents of the Taking the Pulse of the Nation survey. PRIMARY AND SECONDARY OUTCOME MEASURES: The proportion of respondents who had any vaccination, a first dose only, or second dose after the competition opened. RESULTS: Those who entered the competition were 2.27 (95% CI 1.73 to 2.99) times more likely to be vaccinated after the competition opened on 1 October than those who did not enter—an increase in the probability of having any dose of 0.16 (95 % CI 0.10 to 0.21) percentage points. This increase was mostly driven by those receiving second doses. Entrants were 2.39 (95% CI 1.80 to 3.17) times more likely to receive their second dose after the competition opened. CONCLUSIONS: Those who entered the Million Dollar Vax competition were more likely to have a vaccination after the competition opened compared with those who did not enter the competition, with this effect dominated by those receiving second doses.