Benefits of increasing the dose of influenza vaccine in residents of long-term care facilities: A randomized placebo-controlled trial

✍ Scribed by Herman J.M. Cools; Jacobijn Gussekloo; Joyce E.M. Remmerswaal; Ed J. Remarque; Aloys C.M. Kroes

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 92 KB
• Volume: 81
• Category: Article
• ISSN: 0146-6615
• DOI: 10.1002/jmv.21456

✦ Synopsis

Abstract

Increased vaccine doses and mid‐season boosting may increase the proportion of residents with protective immunity from influenza in long‐term care facilities. In a multi‐center study (1997–1998), 815 residents from 14 long‐term care facilities were assigned at random to receive 15 or 30 µg of inactivated influenza vaccine, followed by a 15 µg booster vaccine or a placebo vaccine at Day 84. Seroresponses were re‐analyzed by hemagglutination‐inhibition (≥4‐fold titer increases, protective titer ≥40, geometric mean titers. Forty percent of the participants had pre‐vaccination titers ≥40. At Day 25 after vaccination, this increased to 66.3% after a 15 µg dose versus 73.3% after a dose of 30 µg (P = 0.049). Participants receiving a 30 µg dose followed by a 15 µg booster showed more ≥4‐fold titer increases at Day 109 (43.6% vs. 35.4%, P = 0.003) and protective titers ≥40 (74.2% vs. 64.6%, P = 0.041), compared to those receiving only a 15 µg dose. Differences were most apparent in participants with low pre‐vaccination titers. Booster vaccination after an initial 15 µg dose of the vaccine did not increase the protective rate (61.9% vs. 63.9% after placebo). The number of participants needed to vaccinate to protect one additional resident by a dose of 15 µg was 4, by a dose of 30 µg 3, and 15 when using a 30 µg dose instead of 15 µg. Doubling the dose of influenza vaccine increased protection‐related responses among residents of long‐term care facilities, especially in those with low pre‐vaccination titers. J. Med. Virol. 81:908–914, 2009. © 2009 Wiley‐Liss, Inc.