Human mobility increased with vaccine coverage and attenuated the protection of COVID-19 vaccination: A longitudinal study of 107 countries

Background The World Health Organization has raised con-cerns that vaccinated people may reduce physical and social dis-tancing more than necessary. With imperfect vaccine protection and the lifting of mobility restrictions, understanding how hu-man mobility responded to vaccination and its potential conse-quence is critical. We estimated vaccination-induced mobility (VM) and examined whether it attenuates the effect of COVID-19 vac-cination on controlling case growth.Methods We collected a longitudinal data set of 107 countries between 15 February 2020 and 6 February 2022 from Google COVID-19 Community Mobility Reports, the Oxford COVID-19 Government Response Tracker, Our World in Data, and World Development Indicators. We measured mobility in four catego-ries of location: retail and recreational places, transit stations, grocery stores and pharmacies, and workplaces. We applied pan-el data models to address unobserved country characteristics and used Gelbach decomposition to evaluate the extent to which VM has offset vaccination effectiveness.Results Across locations, a 10-percentage-point (pp) increase in vaccine coverage was associated with a 1.4-4.3 pp increase in mobility (P < 0.001). VM was greater in lower-income coun-tries (up to 7.9 pps; 95% confidence interval (CI) = 5.3 to 10.5, P< 0.001) and in earlier stages of vaccine rollouts (up to 19.2 pps; 95% CI = 15.1 to 23.2%, P < 0.001). VM decreased the ef-fectiveness of vaccines in controlling case growth by 33.4% in retail and recreation places (P < 0.001), 26.4% in transit sta-tions (P < 0.001), and 15.4% in grocery stores and pharmacies (P= 0.002).Conclusions VM provides support for the Peltzman effect; it at-tenuates but does not completely counter vaccine effectiveness. Our study findings suggest strategies for mitigating the unintend-ed consequences of VM, including reducing short-term mobility responses after vaccination, prioritizing mobility in grocery-type places and workplaces, and accelerating rollouts at earlier stages of vaccination, especially in lower-income countries.