aa Belshe 2000a

Methods	See aa Belshe 1998
Participants	1358 healthy children who previously participated in year 1 of trial (aa Belshe 1998). Aged 26 to 85 months
Interventions	Re‐vaccination with live attenuated, cold‐adapted trivalent (H1N1, H2N3 and B) influenza vaccine, administered by nasal spray
Outcomes	Primary end‐point of efficacy: first episode of culture‐confirmed influenza occurring in an individual child after revaccination Subtype specific efficacy (A and B) Influenza: any illness detected by active surveillance associated with positive culture for wild‐type influenza virus Strain‐specific antibody responses to vaccine Adverse reactions: increase in temperature, decreased activity, irritability, runny nose or nasal congestion, sore throat, cough, headache, muscle aches, chills, vomiting, OM Serious adverse events occurring at any time during the study Incidences of flu‐like illness detected by surveillance
Funding Source	Government/Industry
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Second year of study of aa Belshe 1998 not re‐randomised
Allocation concealment (selection bias)	Unclear risk	Second year of study of aa Belshe 1998, not sufficient description
Blinding (performance bias and detection bias) All outcomes	Low risk	Double‐blinding
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	At the start of the second study year (aa Belshe 1998) only 86% in the treatment arm and 83% in the placebo arm, from the first study year (aa Belshe 1998) were enrolled but insufficient information given to the end of this second study year
Summary assessments	High risk	Plausible bias that raises some doubt about the results