Seasonal influenza vaccine delivered by intradermal microinjection: A randomised controlled safety and immunogenicity trial in adults

Influenza vaccines remain largely underused. A promising alternative to current intramuscular vaccines is a trivalent inactivated influenza vaccine (TIV) delivered using a microinjection system to offer a less invasive and possibly more acceptable vaccination. A phase II, multicentre, randomised open-label study in 978 healthy adults (18–57 years) evaluated the immunogenicity and safety of intradermal TIV. Subjects received a 0.1 ml injection of intradermal TIV, containing 9 μg of haemagglutinin (HA) per strain (n = 588) or a conventional 0.5 ml intramuscular vaccine (15 μg of HA/strain; n = 390). Intradermal TIV induced non-inferior humoral immune responses against all three strains and superior responses against both A strains (H1N1, H3N2) compared with the control. Both vaccines were well tolerated.