BackgroundUpdating vaccines is essential for combatting emerging coronavirus disease 2019 (COVID-19) variants. This study assessed the public health and economic impact of a booster dose of an adapted vaccine in the United Kingdom (UK).MethodsA Markov-decision tree model estimated the outcomes of vaccination strategies targeting various age and risk groups in the UK. Age-specific data derived from published sources were used. The model estimated case numbers, deaths, hospitalizations, medical costs, and societal costs. Scenario analyses were conducted to explore uncertainty.ResultsVaccination targeting individuals aged >= 65 years and the high-risk population aged 12-64 years was estimated to avert 701,549 symptomatic cases, 5,599 deaths, 18,086 hospitalizations, 56,326 post-COVID condition cases, and 38,263 lost quality-adjusted life years (QALYs), translating into direct and societal cost savings of 112,174,054 pound and 542,758,682 pound, respectively. The estimated economically justifiable price at willingness-to-pay thresholds of 20,000 pound and 30,000 pound per QALY was 43 pound and 61 pound, respectively, from the payer perspective and 64 pound and 82 pound, respectively, from the societal perspective. Expanding to additional age groups improved the public health impact.ConclusionsTargeting individuals aged >= 65 years and those aged 12-64 years at high risk yields public health gains, but expansion to additional age groups provides additional gains.