| Study characteristics |
| Methods |
Prospective cohort study conducted in New York, USA during the 1982 to 1983 influenza season. Authors investigated an outbreak in a nursing home; independent blind assessment was conducted. Follow‐up period was 1 November 1982 to 30 April 1983. 305 of the 525 residents volunteered to participate in study; diagnosis was made without knowledge of vaccination status |
| Participants |
305 nursing home residents, mostly ambulatory (181 treated and 124 controls; 138 and 94 had serological surveillance, respectively); groups were comparable for health status and drug use; mean age 85 years |
| Interventions |
Parenteral influenza vaccine: A/Bangkok/1/79; A/Brazil/11/78; B/Singapore/222/79. Vaccine strains matched circulating strains (slight drift) |
| Outcomes |
Laboratory‐confirmed influenza (4‐fold increase in antibody titre), X‐ray‐confirmed pneumonia, deaths from all causes |
| Notes |
Pneumococcal vaccine was rarely used. Amantadine was not used. The circulating strain was A/Arizona/80, closely related to A/Bangkok/1/79 Laboratory‐confirmed cases were analysed by intention‐to‐treat |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Low risk |
A ‐ Adequate |
