| Study characteristics |
| Methods |
Prospective cohort study conducted in New York, USA during the 1980 to 1981 influenza season. Authors investigated a nursing home with evidence of flu activity; medical records were reviewed. Comparability between cohorts was assessed by analysis of the underlying conditions of a sample of the population; 62 people with severe organic brain syndrome were excluded. Follow‐up period was 1 November 1980 to 30 April 1981. |
| Participants |
458 residents in nursing home for healthy and ill elderly (244 treated and 214 controls, all included in the analysis); most patients required skilled nursing home care |
| Interventions |
Parenteral influenza vaccine: A/Brazil/78; A/Bangkok/79; B/Singapore/79. Vaccine strains matched circulating strains. |
| Outcomes |
Symptoms defined and radiologically confirmed pneumonia; death from pneumonia within 60 days from the onset of pneumonia |
| Notes |
Vaccinated participants had very slight excess of underlying conditions; smokers were rare; pneumococcal vaccine was rarely used. Specific viral diagnosis was not attempted, but the circulating strain in the community was A/Bangkok/79‐like. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
B ‐ Unclear |
