Inclusion Criteria:  Aged 18 or older at the time of vaccination. Received AZD1222 as the first dose of COVID-19 vaccination in the prior 28 days. The participant has provided sufficient details to validate the vaccination (vaccination card, batch/lot number, and/or regional vaccination register details). Provided informed consent to participate in the study, either personally or through a legal representative. Able and willing to provide responses to study notifications using the mobile device app, web portal, or call centre or have a proxy (a caregiver, family member, or other trusted individual) who can do so on their behalf. Able and willing to grant, personally or through a legal representative, permission to contact the participant's healthcare providers and to access the participant's medical records at the time of vaccination and during the post-vaccination follow-up period.