aa Rytel 1977.
| Methods | Single‐blind randomised controlled trial conducted in the USA during the 1974 to 1975 influenza season. Follow‐up lasted from winter to spring. A "two month" epidemic period was described by the authors with no reference to a definition and lasted 6 weeks. Study participants were randomly assigned into 3 subgroups to receive either 2 doses of the vaccine (n = 47), 1 dose of vaccine and 1 dose of placebo (n = 48), or 2 doses of placebo (n = 48) at 14 days apart. 6‐month sera were collected on all study participants. | |
| Participants | 143 young adult female student nurse volunteers: 95 treated and 48 placebo. Age of participants was 18 to 35. | |
| Interventions | Live attenuated, bivalent, intranasal influenza A (containing 107,2 EID50) and B (containing 107,8 EID50) vaccines. Schedule and dose were single or double doses. Vaccine composition was: A/England/42/72 (H3N2) and B/Hong Kong/5/72. Placebo was 5% sucrose. Vaccine was not recommended and did not match the circulating strain. | |
| Outcomes | Influenza and adverse effects. An influenza case was defined as the presence of an influenza‐like illness (3 or more symptoms of acute respiratory disease and temperature greater then 37.2 °C) and virus isolation and/or 4‐fold rise in antibody titre in sera obtained at 30 days and 6 months following immunisation. Local adverse effects were upper respiratory symptoms and cough. These were subdivided into moderate and severe. A definition of general adverse effects (again distinguished between moderate and severe) was not given. | |
| Notes | 1 dose and 2 doses were analysed together. Circulating strain was A/PortChalmers/1/73 (H3N2). Efficacy and safety data extracted. Government funded |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | Unclear |
| Allocation concealment (selection bias) | Unclear risk | Unclear |
| Blinding (performance bias and detection bias) All outcomes | Unclear risk | Unclear |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | Unclear |
| Summary assessment | Unclear risk | Unclear |