Intradermal influenza vaccine and new devices: a promising chance for vaccine improvement.

INTRODUCTION: The main public health strategy for reducing the influenza burden is annual vaccination. However, because the immune response in the elderly and frail subjects is known to be less vigorous than in younger adults, novel strategies have been explored in the last decade to augment immune response after immunization. These have included an increased dosage, multiple dose vaccinations, use of vaccine adjuvants and more efficient routes of vaccine delivery. AREAS COVERED: This review discusses recent advances in intradermally administered influenza vaccines with particular attention to immunogenicity and safety data from clinical trials performed using appropriate injection systems which, combining consistent injection depth and volume, safety, simplicity and ease-of-use, allowed large scale evaluation. EXPERT OPINION: Substantial experience has been accumulated with Intanza® 9 and Intanza 15 μg/IDflu® 15 μg, administered using BD's Soluvia™ device, and are the first intradermal trivalent inactivated split-virion influenza vaccines to be licensed for use in 18 - 59 year adults and in elderly people, respectively. Clinical data showed that they are safe and immunogenic and can offer significant advantages in terms of higher acceptability, higher immunogenicity in the elderly and dose-sparing in adults younger than 60 years when compared with intramuscularly administered vaccine.