Background: Individuals in contact with persons with COVID‐19 are at high risk of developing COVID‐19; protection offered by COVID‐19 vaccines in the context of known exposure is poorly understood. Methods: Symptomatic outpatients aged ≥12 years reporting acute onset of COVID‐19‐like illness and tested for SARS‐CoV‐2 between February 1 and September 30, 2021 were enrolled. Participants were stratified by self‐report of having known contact with a COVID‐19 case in the 14 days prior to illness onset. Vaccine effectiveness was evaluated using the test‐negative study design and multivariable logistic regression. Results: Among 2229 participants, 283/451 (63%) of those reporting contact and 331/1778 (19%) without known contact tested SARS‐CoV‐2‐positive. Adjusted vaccine effectiveness was 71% (95% confidence interval [CI], 49%–83%) among fully vaccinated participants reporting a known contact versus 80% (95% CI, 72%–86%) among those with no known contact (p‐value for interaction = 0.2). Conclusions: This study contributes to growing evidence of the benefits of vaccinations in preventing COVID‐19 and support vaccination recommendations and the importance of efforts to increase vaccination coverage. [ABSTRACT FROM AUTHOR]