Freitas 2013.

Methods	Case–control study ‐ Brazil ‐ hypersensitivity‐type adverse events and MMR vaccination
Participants	Case‐patients were defined as 1‐ to 4‐year‐old children with suspected HAEs following vaccination with MMR A during the 2004 national campaign and reported to the national AEFI surveillance system by clinicians. Postvaccination HAEs were defined as the acute onset of exanthema, urticaria, or facial or peripheral oedema within 24 h after MMR vaccination during the August 2004 national campaign. For each case, 1 or more asymptomatic children from the same age group vaccinated during the same campaign and residing in nearest‐neighbour households were enrolled as controls. Parents of both case‐patient children with HAEs and their controls were interviewed, from 2 weeks to 2 months after the HAE, using a standardised questionnaire to collect: basic demographic data, medical history of children (including prior vaccinations; history of known allergy to foods (including gelatin, eggs) and antibiotics); history of recurrent respiratory problems (including asthma), and specifics about symptoms observed after receiving MMR vaccination, as well as the type (if any) of medical care received following vaccination. Case‐patient children n = 49; controls n = 185
Interventions	MMR vaccine (manufacturer A B C) MMR_A contains Dextran 70 (Sigma–Aldrich; St Louis, Missouri, USA)
Outcomes	Hypersensitivity‐type adverse events
Notes	Discussion: study highlights the importance of a well‐functioning routine AEFI surveillance system linked with mass vaccination campaigns. Such a system in Brazil permitted timely detection of HAEs and validation of a safety signal associated with 1 vaccine manufacturer. Unlike earlier publications, this outbreak linked to a single manufacturer of MMR showed no association with a prior allergic history to eggs or other foods, including gelatin; subsequent studies implicate the dextran stabiliser in MMR from manufacturer A as the likely cause of HAEs. Note: although cases of hypersensitivity after MMR A vaccine occurred in 7 states, the authors only included suspected cases reported in 2 states (Paraná and Santa Catarina) in this case–control study for logistical reasons. Furthermore, the authors investigated only cases reported to the AEFI surveillance system; they did not conduct active surveillance for other cases that might not have been reported. The description of signs and symptoms was based on the recollections of parents or adults who observed children during the episodes, and were not verified by health professionals. Finally, the last interviews were conducted 2 months after the vaccination campaign began.