Background

AEFI surveillance serves as a quality assurance mechanism for national immunization programmes and, in most countries needs continuous strengthening. There are five possible causes of AEFI: 1/ a true product reaction; 2/ a product defect; 3/ an immunization error; 4/ immunization stress-related response; and 5/ a coincidental health event. It is important to identify and provide care to patients with AEFIs. Serious AEFIs should also be thoroughly investigated to determine their cause.