A phase I evaluation of inactivated influenza A/H5N1 vaccine administered by the intradermal or the intramuscular route

Abstract

In a phase I clinical trial, one hundred healthy young adults were randomized to receive two doses 28 days apart of an inactivated, subvirion vaccine containing 15 or 45microg of influenza A/H5N1 hemagglutinin (HA) by the intramuscular (IM) route, or 3 or 9microg of H5 HA by the intradermal(ID) route. Seventy-seven subjects received a third dose. All regimens were safe and well tolerated. Antibody responses after two or three doses were low (<or=20% or <or=38%, respectively) and similar in groups given 3 or 9microg ID or 15microg IM, and were significantly lower than those given 45microg IM. Higher dosages of H5 HA and/or inclusion of adjuvant will be required to enhance immunogenicity by the ID route.

Figure 1

Percent of subjects with injection site reactions per vaccine group during the week after the first dose of vaccine. Grading for pain/tenderness refers to interference with activity: Grade 1: mild, Grade 2: moderate and Grade 3: severe. Grading for erythema and pigmentation is in terms of size in diameter: Grade 1: Small (<20mm), Grade 2: Medium (20–50mm), and Grade 3: Large (>50mm)