ca Yin 2011

Methods	Prospective cohort study carried out on children aged 6 to 59 months from 2 daycare centres (DCC) and 2 preschool centres (PSC) Effectiveness of trivalent inactivated seasonal vaccine in preventing ILI cases was assessed
Participants	Children from 2 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 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 those from DCC2 and PSC2 acted as control group and did not receive any treatment Immunisation has been performed between 11 July 2007 and 19 September 2007
Outcomes	Laboratory Parents were trained from study nurses in order 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 (HRV), influenza A, influenza B, RSV, adenoviruses, HMPV, 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). Cases were assessed by parents after education for ILI surveillance. This was begun 2 weeks after the 2nd dose among vaccinated and from August 26th, 2007 onwards among controls and was continued up to October 21st, 2007. Households were also invited to monitor ILI symptoms by mail or phone call between July 30th and October 21st, 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 if this was stated in the methods Only 151 out 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 from follow‐up Nasal swab samples had been 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 when 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