ca Wiggs‐Stayner 2006.

Methods	Government‐funded, nurse‐led prospective cohort study carried out in the US state of Indiana. The study was conducted in 4 "entitlement 1" schools, which appear to have been populated by children of a lower socioeconomic class (80% to 90% were in receipt of free school lunches), evenly split between whites and blacks (Table 1 reports detailed ethnic background by school). With a range of students of 264 to 392. Attendance rates were 93.9% to 95.3%.
Participants	In school 1, 277 children aged from 5 years and a number of adults (teachers) up to the age of 49. The criteria for selection were lack of contraindications, lack of self reported ongoing ILI, and parental consent. 51 were "medically excluded", and 143 finally had consent for and received the vaccine. In school 2, the figures were 273 "eligibles", 50 and 134. Overall coverage was 57%. We make the denominators 741 children in non‐vaccinated schools; out of 550 children in schools 1 and 2, 276 were vaccinated and 274 were not eligible for one reason or another.
Interventions	Cold‐adapted recombinant spray vaccine (FluMist) in 2 intranasal doses or no vaccination. Content, degree of matching, or surrounding community viral circulation is not described.
Outcomes	Effectiveness Days enrolled, days present, and days absent during the study period (which is not reported)
Funding Source	Government
Notes	The authors conclude that "the 2 schools receiving FluMist increased their attendance rates from 95.3% and 93.9% to 96.1% and 95.8%. Previously, the comparison schools each had a 94.6% attendance rate; 1 fell to 94.4% and the other rose very slightly to 94.7%. The differences in self‐ or parent‐reported influenza absences were not significant. However, the difference in days absent between individual vaccinated and non‐vaccinated schools was statistically significant" Appalling reporting: no season, vaccine content, or viral circulation, no outcome definition, no incidence of ILI or definition of respiratory illness, selection bias, unclear conclusions, and mixture of 2 designs (before‐and‐after comparisons mixed with prospective cohort). High risk of bias
Risk of bias
Bias	Authors' judgement	Support for judgement
PCS/RCS‐Selection Exposed cohort	High risk	No description
PCS/RCS‐Selection Non Exposed cohort	Unclear risk	Draw from different source
PCS/RCS‐Comparability	Unclear risk	No description
PCS/RCS‐Assessment of Oucome	Unclear risk	Not described
Summary assessments	High risk	No outcome definition, no incidence of ILI or definition of respiratory illness, selection bias, unclear conclusions, and mixture of 2 designs