Clyde B. Schechter, MD
To the Editor: There may be a bias in the ascertainment of vaccination status affecting the results of the study by Sims and colleagues on the effectiveness of pneumococcal vaccine (1). Because study entry as a patient required the isolation of pneumococci from blood, cerebrospinal fluid, or pleural fluid, patients generally had severe acute illness. Consequently, compared with the medical records for the general hospital controls, who typically would be less acutely ill patients, those for patients with severe acute illness may have not contained the names of all care-givers. These patients may also have been more likely to die
Schechter CB. Pneumococcal Vaccine in the Elderly. Ann Intern Med. ;109:594–595. doi: 10.7326/0003-4819-109-7-594
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Published: Ann Intern Med. 1988;109(7):594-595.
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