ca Yin 2011.

Methods	Prospective cohort study carried out on children aged 6 to 59 months from 2 day‐care centres (DCC) and 2 preschool centres (PSC). The study assessed effectiveness of trivalent inactivated seasonal vaccine in preventing ILI cases.
Participants	Children from 2 day‐care centres (DCC1, n = 62 and DCC2, n = 73; age range 6 to 59 months) and 2 preschool centres (PSC1, n = 52 and PSC2, n = 52; age range 24 to 59 months) in Sydney
Interventions	Administered vaccine was Vaxigrip Junior (Sanofi Pasteur, Lyon, France) prepared with the strain recommended for the 2007 season in the Southern Hemisphere: A/New Caledonia/20/99 (H1N1)‐like strain (A/New Caledonia/20/99 IVR‐116) A/Wisconsin/67/2005 (H3N2)‐like strain (A/Wisconsin/67/2005 NYMCX‐161B) B/Malaysia/2506/2004‐like strain Children were immunised with 2 doses of 0.5 mL (0.25 mL if aged less than 36 months) 1 month apart intramuscularly administered. Children from DCC1 and PSC1 were immunised, whereas children from DCC2 and PSC2 acted as control group and did not receive any treatment. Immunisation was performed between 11 July 2007 and 19 September 2007.
Outcomes	Laboratory Study nurses trained parents to collect nasal swabs by means of the Virocult system. Samples were sent by post to the Queensland Paediatric Infectious Diseases Laboratory, where the presence of the following viruses has been investigated: human rhinoviruses, influenza A, influenza B, RSV, adenoviruses, human metapneumovirus, parainfluenza viruses I, II, and III, bocavirus, hPyV‐WU, hPyV‐KI, and human coronaviruses OC43, 229E, NL6332, and HKU1.33. Effectiveness ILI: defined as illness with fever > 37.8 °C and at least 1 respiratory symptom (cough, blocked nose or runny nose). Parents assessed cases after education for ILI surveillance. This was begun 2 weeks after the second dose among vaccinated children and from 26 August 2007 onwards among controls, and was continued up to 21 October 2007. Households were also invited to monitor ILI symptoms by mail or phone call between 30 July and 21 October 2007. Safety Not assessed
Funding Source	Government
Notes	Allocation of DCC and PSC to vaccination or no treatment did not occur randomly (see Discussion), even though this was stated in the Methods. Only 151 of the total 239 children (63%) from DCC 1 and 2 and PSC 1 and 2 were enrolled in the study. 1 vaccinated child from PSC1 was further lost to follow‐up. Nasal swab samples were collected for only 26 out of 59 detected ILI cases. In 18 samples, the presence of at least 1 virus could be assessed; only 2 tested positive for influenza A viruses. At the time the follow‐up was started (mid‐August), the epidemic was peaking. The authors conclude that “No evidence was found for influenza VE but point estimates were all in the direction of protection”.
Risk of bias
Bias	Authors' judgement	Support for judgement
PCS/RCS‐Selection Exposed cohort	Unclear risk	Not clearly described
PCS/RCS‐Selection Non Exposed cohort	Unclear risk	Not clearly described
PCS/RCS‐Comparability	Unclear risk	Not clearly described
PCS/RCS‐Assessment of Oucome	Unclear risk	Self report
Summary assessments	High risk	Plausible bias that seriously weakens confidence in the results