The January 2022 spike in COVID-19 infection rates in the U.S. was three times higher than the December 2020 spike despite widespread vaccination by January 2022 and minimal vaccination in December2020. Moreover, infection rates continued to rise throughout 2021 even as vaccine distribution expanded and coverage increased. To explore this paradox, we develop a model in which agents choose their socialization patterns in the presence of an infectious disease and an imperfectly effective protective measure. As the protective measure becomes more effective or more widely adopted, up to a threshold, infection rates increase due higher socialization rates, despite higher effectiveness and adoption rate of the protective measure. Superspreader agents such as individuals at central points of interest (e.g., schools, gyms, grocery stores) or those in highly connected roles (e.g., teachers, trainers, cashiers) facilitate the transmissions. We provide supporting evidence using U.S. foot traffic data (2021–2022) and historical COVID-19 vaccination and community transmission rates.