<p>Active, sentinel site surveillance (SSS) was implemented in six referral hospitals across all five health zones from September 2022 – July 2023. Data collectors reviewed medical charts of all patients ≥12 years in inpatient and emergency departments to identify conditions and abstract relevant data for one or more of 12 pre-selected AESI: acute disseminated encephalomyelitis, abscess, anaphylaxis, Bell’s palsy, cellulitis, encephalitis, generalized convulsion, myelitis, myocarditis/pericarditis, sudden unexplained death, thrombocytopenia (with and without thrombosis), and toxic shock syndrome. Cases were confirmed using Brighton Collaboration criteria for most conditions followed by ascertainment of COVID-19 vaccination status. All vaccinated cases were referred to the national system for investigation and causality assessment using the WHO Causality Assessment guidelines.</p>