- In this example of a self-control analysis, the incidence of asthma
exacerbations prior to vaccination is compared to the incidence after
the same child. This approach is analogous to a cross-over design in
a clinical trial, where each child serves as his/her own control.
Limitations to this retrospective, non-experimental design are numerous.
In this example, the results could be strongly biased by more aggressive
asthma therapy post-vaccination since, by definition, each patient
would have had multiple exacerbations by the end of the study period.3
Despite the limitations of this study, it provides the first evidence
to support influenza vaccination in an important group of high-risk
pediatric patients. This is especially so since a randomized controlled
trial designed to address this question may not be ethical.
P, DeStefano F, Gargiullo PM, Chen RT, Lieu TA, Davis RL, Mullooly JP,
Black SB, Shinefield HR, Boblke K, Ward JI, Marcy SM, and the Vaccine
Safety Datalink Team. Does influenza vaccination prevent asthma exacerbations
in children? J Pediatr 2001;138:306-310.
Academy of Pediatrics. Influenza. In: Pickering LK, editor. 2000 Red
Book: Report of the Committee on Infectious Diseases 25th ed. Elk Grove
Village (IL): American Academy of Pediatrics; 2000. p. 356.
KM. Influenza vaccine in children with asthma: Why no progress? J