Abstract
Vaccination is the only way to reach herd immunity and help people return to normal life. However, vaccination rollouts may not be as fast as expected in some regions due to individuals' vaccination hesitation. For this reason, in Detroit, Michigan, the city government has offered a $50 prepaid card to people who entice city residents to visit vaccination sites. This study examined vaccination rates in the US using Detroit, Michigan, as the setting. It sought to address two issues. First, we analyzed the vaccination diffusion process to predict whether any region would reach a vaccination completion level that ensures herd immunity. Second, we examined a natural experiment involving a vaccination incentive scheme in Detroit and discovered its causal inference. We collected weekly vaccination data and demographic Census data from the state of Michigan and employed the Bass model to study vaccination diffusion. Also, we used a synthetic control method to evaluate the causal inference of a vaccination incentive scheme utilized in Detroit. The results showed that many Michigan counties—as well as the city of Detroit—would not reach herd immunity given the progress of vaccination efforts. Also, we found that Detroit's incentive scheme indeed increased the weekly vaccination rate by 44.19% for the first dose (from 0.86 to 1.25%) but was ineffective in augmenting the rate of the second dose. The implications are valuable for policy makers to implement vaccination incentive schemes to boost vaccination rates in geographical areas where such rates remain inadequate for achieving herd immunity.
Highlights
The length of the COVID-19 pandemic has surpassed 1 year and continues unabated in numerous geographical locales
Despite the putative benefit of the vaccination incentive scheme, the Bass model predicted that Detroit would not reach a vaccination level high enough to achieve herd immunity, yet ∼24.1% of counties in Michigan would likely engender a vaccination rate exceeding 60%
The result shows that Bass model considerably outperforms Gompertz and Logistic diffusion models for all counties
Summary
The length of the COVID-19 pandemic has surpassed 1 year and continues unabated in numerous geographical locales. Such endeavors affords countries ability to move on to a new phase of the pandemic As this new phase unfolds, of particular importance is whether herd immunity will be achieved through mass vaccination programs. Despite the putative benefit of the vaccination incentive scheme, the Bass model predicted that Detroit would not reach a vaccination level high enough to achieve herd immunity, yet ∼24.1% of counties in Michigan would likely engender a vaccination rate exceeding 60%. Given this finding, we suggest that offering incentives at an early stage and for the second doses, as well as education, and targeting certain age groups would be salutary. This study offers valuable and timely important implications for policy makers to augment vaccination rates whether vaccination rollouts are currently underway or will begin imminently
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