This longitudinal study integrates exposure effects and confirmation bias under the theoretical framework of dynamic motivation activation (DMA) to examine the dynamic reciprocity of misinformation, misperceptions, and attitudes in the context of COVID-19 vaccination. Results from a three- national survey showed that misinformation exposure, misperceptions, and attitudes toward COVID-19 vaccines reinforced themselves over time. Further, misperceptions reduced subsequent pro-vaccine attitudes, and pro-vaccine attitudes in turn decreased subsequent misperceptions. Longitudinal mediation analysis also indicated that attitudes reinforced themselves through misperceptions. Surprisingly, we did not find a significant impact of misinformation exposure on subsequent misperceptions or effects of attitudes on subsequent misinformation exposure. These findings highlight the importance of addressing misperceptions regarding COVID-19 vaccines and provide insights for theoretical development in research on exposure effects and confirmation bias.