key: cord-0994571-lo8e2q5b authors: Jun, D.; Scott, A. title: An observational study of the association between COVID-19 vaccination rates and participation in a vaccine lottery date: 2022-03-04 journal: nan DOI: 10.1101/2022.03.02.22271734 sha: 626384cb708366a93a2154ed181cc78feac79f72 doc_id: 994571 cord_uid: lo8e2q5b Objectives Are financial incentives from entry in a vaccine lottery associated with a higher 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 2,375 respondents of the Taking the Pulse of the Nation Survey Interventions Participation in the Million Dollar Vaccination Lottery Primary and secondary outcome measures The proportion of respondents who had any vaccination, a first dose only, or second dose compared to all other respondents Results Those who participated in the lottery were 2.27 times more likely to be vaccinated after the lottery opened on October 1st than those who did not. This was driven by those receiving second doses. Lottery participants were 1.38 times more likely to receive their first dose after October 1st and 2.31 times more likely to receive their second dose after October 1st. Conclusions Lottery participation is associated with a higher vaccination rate, with this effect dominated by a higher rate of second doses. There is a smaller insignificant difference for those receiving a first dose, suggesting lotteries may not be as effective at reducing vaccine hesitancy, compared to 'nudging' people to get their second dose more quickly. 3 The effectiveness of using financial incentives to increase vaccination rates for the SARS-COV-2 virus is uncertain. [1] [2] [3] Vaccination lotteries were established to increase vaccination rates, including across at least 21 states in the United States in 2021. Most notable is the lottery in Ohio run during May-June 2021 with 5 x $1 million prizes over five weeks. Four studies using state-level data on vaccination rates over time, and comparing states with lotteries with those with none, found lotteries were ineffective in increasing vaccination rates. [4] [5] [6] [7] Four studies found an increase in vaccination rates [8] [9] [10] [11] , including one that found increases in vaccination rates in low-income counties in Ohio but not in high-income counties. 9 One study examined the use of financial incentives across 24 states across the U.S., mainly including lotteries, and found no overall impact on vaccination rates. 12 Our research uses individual-level data to examine the association between vaccination rates and participation in a vaccination lottery held in Australia in October 2021. The Million Dollar Vaccination Lottery (M$V) was open to entries from 1 st to 31 st of October 2021 for those aged 18 years or over who were Australian residents. Unlike some U.S. lotteries where the whole population was automatically entered the lottery, in M$V, each person entered voluntarily by completing a short webform providing their contact details. At entry, participants could already be fully vaccinated or have had the first vaccination. Proof of vaccination was not required at entry into the lottery though individuals had to tick a box on the webpage stating that they had at least their first dose. If they were chosen to receive a prize (a provisional winner), they were required to show proof of full vaccination in the form of a government-approved electronic vaccination certificate. To claim a prize full vaccination must have occurred before 13 th December, or no later than 13 th January, depending on the required interval between first and second doses, which may vary across States and be up to 12 weeks. Only one entry per person was allowed. M$V was funded by an alliance of philanthropic organisations coordinated by the Summer Foundation. The lottery had a $AU 1 million ($US 0.72 million) Grand Prize in cash and a total of 3,100 daily prizes of $AU 1,000, with a total prize pool of $AU 4.1 million. Each entrant was eligible for the Grand Prize draw and the daily draw on the entry date. The daily prizes were in the form of a gift card that could be used at a range of participating stores. The lottery was accompanied by a $AU 3 million marketing campaign led by Sayers that included peak-time TV, radio, and full-page national and regional newspaper advertising, extensive social media advertising, and outdoor media (e.g., electronic posters at bus stops and shopping centres). The campaign targeted culturally and All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. linguistically diverse audiences and included advertising in languages such as Mandarin, Arabic, Cantonese, and Vietnamese, and areas with high populations of Indigenous people. As the campaign progressed, the targeting became more granular and nuanced in response to the analysis of data regarding the reach of the campaign, competition entrants, and vaccination rates in specific geographic locations throughout Australia. In response to concerns raised on social media about M$V being a scam, the campaign pivoted to engage and profile daily draw winners in paid and to provide social proof about the legitimacy of M$V. When the lottery closed, 2,744,974 Australians had entered, representing 13.7% of the adult population. The context of the lottery was when Australia was well on its way to meeting vaccination targets. Australia's vaccination program started in March 2021. On the 30 th of September, just before the lottery opened, vaccination rates had steadily increased to 77.8% percent of the population over 16 years old with a first dose and 54.2% with a second dose. New South Wales (NSW) and Victoria, the two most populous states, had experienced outbreaks since July 2021 and were under various forms of lockdown at the end of September, including night-time curfews in Victoria, closure of retail businesses and hospitality, and continuing bans on travel. Lockdowns in NSW were more targeted at specific LGAs with high case numbers. All eight states and territories agreed to a national roadmap on the 6 th of August, with states individually releasing precise targets of population vaccination rates that were linked to the lifting of restrictions throughout the last quarter of 2021, with some targets being at the time the lottery was open. For example, in Victoria, the targets were 70% of the population aged 16 and over, (reached on 21 st October), 80% (reached on 29 th October), and 90% of 12+ years (reached on 18 th November) with second dose. These targets provided nonfinancial incentives to get a second dose (referred to as 'fully vaccinated' at the time) as restrictions were eased when targets were met, with restrictions largely non-existent after the 90% target was reached. The lottery provided the potential to receive financial incentives to encourage receipt of the first dose for those not vaccinated and provided incentives to those with a first dose to schedule a second dose if they had not already done so. Those with a first dose may already have had their second dose scheduled during October given the recommended fixed interval between doses, and so the lottery would not influence this group unless they changed their scheduled appointment to receive their second dose earlier. There were also those with a first dose who had not scheduled their second at the time the lottery opened. Those who already All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted March 4, 2022. ; https://doi.org/10.1101/2022.03.02.22271734 doi: medRxiv preprint had their second dose before the lottery opened could still enter the lottery, but their vaccination status would not be affected by the lottery. Patient and public involvement statement. There was no patient or public involvement in this study. Data and participants. The Taking the Pulse of the Nation (TTPN) Survey was used to collect data. This is run by the Melbourne Institute and was administered every week from April 2020 and every two weeks from January 2021. Each wave includes 1,200 respondents, so it is a repeated cross-section. This paper uses data from 2,400 respondents in Waves 44 and 45 conducted in November 2021 after the lottery was closed at the end of October. Data were collected by a commercial provider using a mixed-mode procedure. For each wave, Study design and hypothesis. This is a cross-sectional observational study that examines the association between entering the lottery and the probability of receiving a vaccination after the lottery opened on October 1st. The study design exploits information on the month individuals received their first or second dose of a COVID vaccine which was asked in Waves 44 and 45 after the lottery had closed. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (5) , I have had the first and second dose of the vaccine." If they answered option (4) they were asked the month of their first vaccination. If they answered option (5), they were asked the month of their second vaccination. They were separately asked, "Did you enter the Million Dollar Vax Lottery? (1) Yes, 2) No." The main outcome variable is binary and equal to one for those who reported receiving any vaccination (first or second dose) after the lottery opened in October and is zero for the rest of respondents (including those who remained unvaccinated or those who received their first or second dose before October). In addition, we also separately analysed those who had their first dose after the lottery opened and those who had their second dose after the lottery opened. TTPN asks a range of questions known to be associated with vaccination status, so these were included as independent variables in the analysis. We include indicators for male, age LGAs with low vaccination rates, and so LGA vaccination rates would be associated with participation in the lottery. We, therefore, merge data on LGA-level vaccination rates using each respondent's postcode of residence. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. Statistical analysis. Data are analysed using logistic regression using the outcome variable (vaccinated after October 1 st , 2021) and the above covariates as independent variables to adjust for observed differences between those participating in the lottery and those who did not. Separate regressions are conducted for those receiving their first vaccination after October 1 st and those receiving their second vaccination after October 1st. Results are reported as odds ratios and marginal effects of the difference in the probability of being vaccinated. We exclude respondents who did not know the month they were vaccinated. Of 2,400 respondents, 2,375 responded to the vaccination question. A further 13 respondents did not know the month they received their first vaccination, leaving 2,362 for the analysis of receipt of the first dose. At the time survey was completed in November, after the lottery had closed, 59.9% of all respondents had received two doses, 6.1% had only their first, and 22.3% were willing to be vaccinated but had not yet received their first dose, 7% were unwilling to be vaccinated, and 4.7% were unsure. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. Those who participated in the lottery were more likely to be female, slightly more likely to be under 35, more likely to be between 50 and 64 years old, and less likely to be over 65. Those who participated in the lottery were likely to have a higher income. There was also a higher proportion of lottery participants from Victoria. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (18 -24) , income below 25 percentile, education below high school, being out of labour force or do not know the industry that they are in, living in NSW, without voting preference, and indifferent policy satisfaction. Table 3 examines who is more likely to participate in the lottery. Males were less likely to do so compared to females. Relative to those aged 18-24, respondents aged 50-54 were more likely to be in the lottery, while those older than 65 were less likely to enter. Compared to those in the lowest income quartile, people in the highest income quartile were more likely to enter the lottery. Those working in manufacturing, electricity, gas, water services, 1 1 accommodation and food services, transport, postal and warehousing, and financial and insurance services were less likely to enter the lottery than those who were not in the labour force. Respondents in LGAs with higher vaccination rates were more likely to enter the lottery. Compared to those living in NSW, respondents living in Victoria, Queensland, and Western Australia were more likely to enter the lottery. This study finds evidence of a statistically significant association between lottery LGAs with low vaccination rates and so was more focused on tackling vaccine hesitancy. However, vaccine hesitancy is determined by a complex range of factors that financial incentives do not directly address. Lotteries may be more effective as 'nudges' for those who are already motivated to get vaccinated but have not yet arranged their appointments. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. 4 7-9 11 , three found evidence of an effect of lotteries. 8 9 11 Of two studies that examined second doses 4 5 , only one found an effect of the lottery. 5 Two studies 6 10 used the total rate of vaccinations combining first and second doses and one of these found an effect 10 . The Ohio lottery and M$V were designed differently, implemented at different times during the pandemic, and may have had different marketing campaigns and this may influence the results. The whole population of Ohio was eligible to win and many may not have known about the lottery and so were not motivated to get vaccinated. In the U.S. at that time the rate of vaccination was slowing, suggesting a lack of motivation in the population. The M$V lottery, however, required individuals to enter and allowed individuals entry if they had already been fully vaccinated. In addition, October 2021 was a time when vaccination rates were steadily increasing and when vaccinations targets focussing on second doses ('fully' vaccinated) had been set by some states that were linked to the lifting of harsh lockdowns. Generally, the Australian population was more motivated to get vaccinated and the M$V lottery added to this motivation. People who were already fully vaccinated may have interpreted the lottery as a reward for their patience during lockdowns and for their earlier decision to get vaccinated, and for this group therefore the lottery did not influence their decision to get vaccinated. Our results found that those with higher incomes were more likely to participate in the M$V lottery which is opposite to expectations. Those on lower incomes are more likely to participate in lotteries generally 13 14 . Our result maybe because of the specific context of COVID-19 where a large proportion of the population was or had been in a severe lockdown, and so the lottery was also perceived as a reward for their patience and for already being vaccinated and that this perception was more widely held by those with higher incomes. The results also showed that those in LGAs with higher vaccination rates were more likely to enter the lottery compared to LGAs with lower vaccination rates, again suggesting that those who might have already been vaccinated before October 1 st were more likely to enter. The All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted March 4, 2022. ; https://doi.org/10.1101/2022.03.02.22271734 doi: medRxiv preprint M$V marketing campaign targeted LGAs with lower vaccination rates. Our results suggest that targeted marketing to persuade people to enter a vaccine lottery could be less effective in vaccine-hesitant populations where vaccination decisions are determined by a more complex range of factors that influence access, information, and beliefs 15 . Vaccine lotteries could be more effective as 'nudges' for people to get their second dose more quickly. We do not examine the overall vaccination rate but the timing of when people received their second vaccination, so our numerical results are not comparable to those from other studies that use changes over time in population vaccination rates or the number of vaccines administered. Our data are self-reported and there is a risk of over-reporting of vaccination rates due to social desirability bias. However, this is unlikely as our self-reported rate of second vaccinations of 59.9% in the sample is lower than official data at the time it was collected (77.5% on November 1 st and 87% on November 30 th ). This also raises concerns about the representativeness of our sample. Though our sample is representative of states and territories and uses weights based on location, gender, and age, it is from a commercial panel where respondents might be different from the general population who do not participate in commercial panel surveys in ways we do not observe that might be correlated with lottery participation or vaccine hesitancy. For example, 17% of our sample participated in the M$V lottery compared to the national estimate of 13.7%. The role of financial incentives to increase vaccination rates remains unclear, with some evidence suggesting that direct cash transfers might be more effective than lotteries 3 13 16 17 , but would also be more costly to implement on a population level. Further research should directly compare lotteries and cash transfers with other strategies 16 to increase vaccination uptake and reduce vaccine hesitancy, though such strategies depend on the context and the stage of the pandemic and may interact with other strategies to increase vaccination rates, particularly in vaccine-hesitant populations where other factors are likely to matter more than financial incentives. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted March 4, 2022. ; https://doi.org/10.1101/2022.03.02.22271734 doi: medRxiv preprint Strategies for addressing vaccine hesitancy -A systematic review Financial Incentives for COVID-19 Vaccination Incentives for Immunity -Strategies for Increasing Covid-19 Vaccine Uptake Association Between Statewide COVID-19 Lottery Announcements and Vaccinations Did Ohio's vaccine lottery increase vaccination rates? A pre-registered, synthetic control study: Mimeo Lottery-Based Incentive in Ohio and COVID-19 Vaccination Rates Impact of Vax-a-Million Lottery on COVID-19 Vaccination Rates in Ohio Conditional Cash Lotteries Increase COVID-19 Vaccination Rates COVID-19 financial lottery effect on vaccine hesitant areas: Results from Ohio's Vax-a-million program Implementation of State Vaccine Incentive Lottery Programs and Uptake of COVID-19 Vaccinations in the United States The Ohio Vaccine Lottery and Starting Vaccination Rates Association Between Statewide Financial Incentive Programs and COVID-19 Vaccination Rates A Model of Lottery Participation. Demographics, Context, and Attitudes Relationships between socio economic status and lottery gambling across lottery types: neighborhood level evidence from a large city Communicating with patients and the public about COVID 19 vaccine safety: recommendations from the Collaboration on Social Science and Immunisation Covid-19 vaccination hesitancy Guaranteed Financial Incentives for COVID-19 Vaccination: A Pilot Program in North Carolina No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity This research was funded by the Summer Foundation (grant number: N/A) and used data from The Taking the Pulse of the Nation (TTPN) Survey run by the Melbourne Institute: Applied Economic and Social Research, University of Melbourne. AS conceived of the study, secured funding, designed the survey questions, contributed to the analysis, wrote and revised the manuscript, and interpreted results. DJ prepared the data and conducted all statistical analyses, contributed to writing and revising the manuscript, and interpreting results. None declared. Statistical code for the analysis s available from the Dryad repository, DOI: https://doi.org/10.5061/dryad.rv15dv495. TTPN Survey is a proprietary data set and researchers interested in replication need to seek access to the TTPN survey by contacting the Melbourne Institute.