ca Maeda 2004a.

Methods	Prospective open cohort study of inactivated TIV over 3 seasons in Japan. Placebo was not used for ethical reasons. Children came to hospital if they developed febrile illness within 48 hours of inoculation. The follow‐up period was from January to April of each year.
Participants	175 children were given vaccine every November or December of 1999, 2000, or 2001. For the control group, 171 aged‐matched children in good health who had not received influenza vaccine within 1 year of enrolment were randomly assigned from medical records of hospitals.
Interventions	Inactivated vaccines for the 3 seasons: 1999/2000 ‐ A/Beijing/262/95 (H1N1) 200 CCA/mL*, A/Sydney/5/97 (H3N2) 350 CCA/mL*, and B/Shandong/7/97 2000/2001 ‐ >15 µg haemagglutinin/0.5 mL A/New Caledonia/20/99 (H1N1), A/Panama/2007/99, and B/Yamanashi/166/98 2001/2002 ‐ >15 µg haemagglutinin/0.5 mL A/New Caledonia/20/99 (H1N1), A/Panama/2007/99, and B/Johannesburg/5/99
Outcomes	Serological Influenza A virus infection determined using Becton Dickinson Directigen Flu‐A antigen test performed according to direction of manufacturer. Test utilises enzyme‐conjugated monoclonal antibodies. Effectiveness Influenza A infection. If temperature > 38 °C throat swab taken and tested for influenza A. Safety N/A
Funding Source	Government
Notes	The authors conclude that in small children younger than 24 months the vaccine is not protective. The authors report that there were no complications and no hospitalisations.
Risk of bias
Bias	Authors' judgement	Support for judgement
PCS/RCS‐Selection Exposed cohort	Unclear risk	Insufficient description
PCS/RCS‐Selection Non Exposed cohort	Unclear risk	Matched infants in good health
PCS/RCS‐Comparability	Unclear risk	Matched infants
PCS/RCS‐Assessment of Oucome	Unclear risk	Laboratory
Summary assessments	High risk	Selection bias may be at play as the enrolment procedure is not described.