Vaccination incentives have been in the news again this week, as steel building product manufacturer Steel and Tube began paying its workers $150 to get vaccinated, and Auckland Airports Park & Ride vaccination centre began daily prizes worth $70,000 in total. And in terms of extreme incentives, you have both Air New Zealand and Ryman Healthcare proposing policies to make vaccinations mandatory for all of their employees.
Vaccination incentives have been undergoing debate in the 'pages' of The Conversation over the last few months (see here and here and here). It's also a topic that I have commented on before (see here and here). Both of my posts referenced the Vax-A-Million lottery incentive in Ohio. So, I was interested to read this recent working paper by Andrew Barber and Jeremy West (both University of California, Santa Cruz), that evaluates the impact of the Ohio lottery on coronavirus vaccinations, cases, and hospitalisations.
The Ohio lottery began on 12 May 2021 and ran until 20 June 2021, and Barber and West use daily data covering the period from 19 February to 18 July. They compare Ohio with a synthetic control, which is derived from shares of other states (mostly Wisconsin, Kansas, Michigan, Idaho, and North Dakota) that had a similar trajectory prior to the lottery for both cases and relevant control variables. They find that there is:
...an increase in COVID-19 vaccinations in Ohio that begins almost immediately after the Vax-A-Million announcement and persists past the final prize drawing. Relative to the synthetic control, the program causes a 0.7 percentage points (1.5 percent) increase in the share of state population receiving at least a first dose of a COVID-19 vaccine by the program’s end date, with most of this effect occurring within two weeks of the announcement. In levels, this amounts to about 82,000 people who were persuaded to vaccinate by the CCL incentive, implying an average program cost of 68 dollars per “complier.” For context, this cost-per-complier is less than the 80 dollars in direct costs that the federal government pays a healthcare provider to fully vaccinate one person...
The results are even more compelling when you see them as a picture. Here's their Figure 2 (panel (a)), which shows the difference between the national vaccination rate, and the rates in Ohio and 'synthetic Ohio':
That doesn't look like a big difference, but the trajectory is clearly changed for Ohio (relative to synthetic Ohio) after the vaccination lottery starts. It is easier to see in panel (b) of the same figure, which shows the difference:
The difference in vaccination rates jumps up soon after the lottery starts, and remains higher thereafter. There are similar results for COVID cases, but with a lag (which is to be expected, because the vaccination takes some time to reach full effectiveness). From their Figure 3, panel (b):
And similar again for hospitalisations, with a further lag (because it takes time for cases to get hospitalised). From their Figure 4, panel (b):
You may have read about other research on the Ohio lottery, questioning its effectiveness. Barber and West address that in their paper:
Walkey et al. (2021) conduct an interrupted time series study of Ohio versus the United States during the few weeks surrounding the lottery announcement, concluding that Ohio’s program does not increase vaccination rates. However, Ohio’s vaccination rates track poorly with national rates during the pre-treatment period—a factor motivating our synthetic control identification strategy. Lang et al. (2021) use the classic SCM to study how Ohio’s program affects the share of fully vaccinated residents, finding no effect. This null effect could be because lottery eligibility only required a single dose rather than full vaccination. In addition, their study stops at the final lottery drawing, weeks before many lottery-eligible participants could have obtained a second dose of a vaccine series, which require 21 or 28 day gaps between doses... Finally, Brehm et al. (2021) use county-level data from Ohio, Indiana, Michigan, and Pennsylvania to conduct pooled SCM and state-border difference-in-differences estimations of how Ohio’s program affects the number of first dose vaccinations during the treatment period. The study finds an effect on vaccinations that is very similar in magnitude to that we show here.
What we can take away from this is that the Ohio vaccination lottery appears to have increased the vaccination rate, decreased COVID cases, and decreased hospitalisations. And all at a cost of US$68 per additional vaccination. To get to 90% of people with at least one dose, we need to vaccinate another 800,000 people. At US$68 per vaccination, that's about NZ$76 million. Seems like a steal to me, especially when a Level 3 lockdown in Auckland alone has been estimated to cost $45 million per day. Even if you paid out US$68 on average to everyone, including those that have already been vaccinated, it would still be a good deal.
[HT for the Barber and West study: Marginal Revolution]
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