Background Microneedle patches provide an alternative to conventional needle-and-syringe immunization, and potentially offer improved immunogenicity, simplicity, cost-effectiveness, acceptability and safety. We describe safety, immunogenicity and acceptability of the first-in-human study on single, dissolvable microneedle patch vaccination against influenza. Methods The TIV-MNP 2015 study was a phase 1, partially blinded, placebo-controlled, randomized clinical trial conducted at Emory University that enrolled non-pregnant, immunocompetent adults (age 18–49 years) from Atlanta (USA) and naïve to 2014–2015 influenza vaccine. Participants were equally randomized among four groups and received a single dose of inactivated influenza vaccine 1) by microneedle patch or 2) by intramuscular injection, or received 3) placebo by microneedle patch, all administered by an unblinded healthcare worker; or received 4) inactivated influenza vaccine by microneedle patch self-administered by study participants. Primary safety outcomes were reactogenicity, grade 3 adverse events and serious adverse events within 8, 28 and 180 days and secondary safety outcomes were new-onset chronic illnesses within 180 days and unsolicited adverse events within 28 days all analyzed by intention to treat. Secondary immunogenicity outcomes were antibody titers at day 28 as well as seroconversion and seroprotection rates all determined by hemagglutination inhibition antibody. The trial is completed and registered with ClinicalTrials.gov, NCT02438423. Findings Twenty-five participants per group were enrolled between June 23 and September 25, 2015. There were no related serious adverse events, no related grade 3 or higher adverse events and no new-onset chronic illnesses. Overall incidence of solicited and unsolicited events was similar among vaccinated groups. Reactogenicity was mild, transient and most commonly reported as tenderness at 60% (95% CI, 39– 79%) and pain at 44% (95% CI, 24–65%) after intramuscular injection and tenderness at 66% (95% CI, 51–79%), erythema at 40% (95% CI, 26–55%) and pruritus at 82% (95% CI, 69–91%) after vaccination by microneedle patch application The geometric mean titers were comparable at day 28, between the microneedle patch administered by healthcare worker and the intramuscular route with values of 1197 (95% CI, 855– 1675) and 997 (95% CI, 703–1415) (p=0.5), respectively, for the H1N1 strain; 287 (95% CI, 192–430) and 223 (95% CI, 160–312) (p=0.4), respectively, for the H3N2 strain and 126 (95% CI, 86–184) and 94 (95% CI, 73–122) (p=0.06), respectively, for the B strain. Similar GMT titers were observed in participants who self-administered the microneedle patch. The seroconversion rates were significantly higher at day 28 after microneedle patch vaccination compared to placebo and were comparable to intramuscular injection. Interpretation Use of dissolvable microneedle patches for influenza vaccination was well-tolerated and generated robust antibody responses. Funding National Institutes of Health.

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