The Efficacy of the 2023-2024 Updated COVID-19 Vaccines Against COVID-19 Infection

Inclusion Criteria: * Age ≥18 years * Previously received ≥ 2-doses of US FDA-authorized mRNA vaccines * Comfortable reading and responding to text messages and emails sent in English or having an interpreter assist them * Plan to remain in the greater Salt Lake City area for the next 12 months * Daily access to the internet (via cell phone, laptop, desktop, or tablet) and a phone with text messaging capabilities * Willingness to complete weekly symptom and illness surveillance surveys sent via text and email * Willingness to complete an online survey at enrollment, mid-study, and end-of-study surveys * Willingness to be contacted periodically by study staff via text, email, and/or telephone as part of study activities * Willingness to self-collect rapid antigen tests (RAT; approved by FDA EUA for COVID-19 detection) weekly and when prompted for study purposes, and to send results via the study portal * Willingness to self-collect additional rapid antigen test (approved by FDA EUA for COVID-19 detection) if experiencing a qualifying symptomatic illness or upon RAT-confirmation of an asymptomatic infection * Willingness to attend in-person visit to receive supply of rapid antigen tests and training on their use (all participants) and to receive a COVID-19 booster (if in randomized group) Exclusion Criteria: * Lives with another person who is already enrolled in this study as reported by the subject on the Eligibility Survey (Appendix C. Eligibility Survey) * Previous hypers…