| Study characteristics |
| Methods |
Authors investigated an outbreak in an intermediate and domiciliary care nursing home, in Maryland, USA during the 1987 to 1988 influenza season; medical records were reviewed. Follow‐up period was 8 January 1988 to 26 January 1988. Throat swabs and acute sera specimens were obtained from some ill residents. |
| Participants |
126 nursing home residents (87 treated and 34 controls were included in the analysis; data on immunisation status for 5 residents were not available), mean age 87 years |
| Interventions |
Parenteral influenza vaccine: A/Taiwan/1/86; A/Leningrad/360/86; B/Ann Arbor/1/86. Vaccine strains did not match the circulating strain. |
| Outcomes |
Clinically defined ILI (fever 99.8 °F or greater + 1 of the following: cough, congestion, sore throat) or positive throat culture; pneumonia; deaths were also reported but not by immunisation status |
| Notes |
Vaccinated and not vaccinated participants were similar as underlying conditions, only senile dementia was more frequent in vaccinees. The circulating strain was A/Leningrad‐like. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
B ‐ Unclear |
