| Autor: |
Kristina Baum, Rhonda B. Friedman, Susan Sedory Holzer, Carol Brignoli Gable |
| Rok vydání: |
1991 |
| Předmět: |
|
| Zdroj: |
JAMA: The Journal of the American Medical Association. 265:2194 |
| ISSN: |
0098-7484 |
| DOI: |
10.1001/jama.1991.03460170047030 |
| Popis: |
In Reply.— We conducted a retrospective observational study of the effectiveness of pneumococcal vaccination by examining a "real world" cohort of vaccinated persons in the year before and after vaccination. An age- and sex-matched comparison group served only as a reference for pneumonia prevalence in the subsequent year. This design reduced the potential confounding from external factors by using persons as their own controls and objectively supports the outcomes by identifying the 2-year trend in pneumonia without vaccination. 1 Drs Weiss and Foy expressed concern about using persons as their own controls because the high pneumonia rate prior to vaccination might regress to the mean in the subsequent year. In general, this is a valid concern, especially in studies where subjects are selected with abnormally high or low biological variables and no comparison cohort is followed up. 2 However, pneumonia presents a different situation because it is a condition that |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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