Background: This study was designed to evaluate the efficacy and safety of cold-adapted influenza vaccine, trivalent (CAIV-T) against culture-confirmed influenza in children 12 to <36 months of age during 2 consecutive influenza seasons at multiple sites in Asia.
Methods: In year 1, 3174 children 12 to <36 months of age were randomized to receive 2 doses of CAIV-T (n = 1900) or placebo (n = 1274) intranasally ≥28 days apart. In year 2, 2947 subjects were rerandomized to receive 1 dose of CAIV-T or placebo.
Results: Mean age at enrollment was 23.5 ± 7.4 months. In year 1, efficacy of CAIV-T compared with placebo was 72.9% [95% confidence interval (CI): 62.8–80.5%] against antigenically similar influenza subtypes, and 70.1% (95% CI: 60.9–77.3%) against any strain. In year 2, revaccination with CAIV-T demonstrated significant efficacy against antigenically similar (84.3%; 95% CI: 70.1–92.4%) and any (64.2%; 95% CI: 44.2–77.3%) influenza strains. In year 1, fever, runny nose/nasal congestion, decreased activity and appetite, and use of fever medication were more frequent with CAIV-T after dose 1. Runny nose/nasal congestion after dose 2 (year 1) and dose 3 (year 2) and use of fever medication after dose 3 (year 2) were the only other events reported significantly more frequently in CAIV-T recipients.
Conclusions: CAIV-T was well tolerated and effective in preventing culture-confirmed influenza illness over multiple and complex influenza seasons in young children in Asia.
From the *Department of Microbiology and Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong; Departments of †Microbiology and ‡Health, Research Institute for Tropical Medicine, Muntinlupa City, Philippines; §Department of Paediatrics, University of Malaya Medical Centre, Kuala Lumpur, Malaysia; ∥Queen Sirikit National Institute of Child Health, Bangkok, Thailand; ¶Beijing Children's Hospital, Beijing, China; #Department of Pediatrics, College of Medicine, **Department of Pediatrics, College of Public Health, National Taiwan University Hospital, Taipei, Taiwan; ††Department of Paediatrics, National University Hospital, Singapore; ‡‡Laboratory of Virology, Capital Institute of Pediatrics, Beijing, China; §§Department of Paediatrics, Phramongkutklao Hospital, Bangkok, Thailand; ∥∥Department of Paediatrics, Charoenkrung Pracharak Metropolis Hospital, Bangkok, Thailand; ¶¶Department of Paediatrics, Sri Avittam Tirunal Hospital Medical College, Trivandrum, India; ##Department of Child Health and Paediatric Haemato-Oncology, Christian Medical College and Hospital, Vellore, India; aWyeth Vaccines Research, Pearl River, NY, and bWyeth Vaccines Research, Tokyo, Japan.
Accepted for publication March 22, 2007.
Address for correspondence: John S. Tam, PhD, Wyeth Research, 401 N. Middletown Road, Pearl River, NY 10965; E-mail: firstname.lastname@example.org.