Kongchanagul A, Samnuan K, Wirachwong P, et al. - Given that the evolution and spread of highly pathogenic avian influenza (H5N1) viruses have increased global concerns of a likely human pandemic, and a prime-boost vaccination strategy has been shown to induce robust and broadly cross-reactive antibody responses against the hemagglutinin globular head domain, researchers used serum samples obtained from the prior study, to specifically measure antibodies against the conserved hemagglutinin stem region. They also investigated if the prime-boost regimen can also induce stalk-reactive antibodies. From 60 participants, serum samples obtained prior to vaccination and on days 7, 28 and 90 after boosting vaccination were employed. Two doses of live attenuated H5N2 vaccine (LAIV H5N2) followed by one dose of inactivated H5N1 vaccine a year later were administered to 40 participants, while only the inactivated H5N1 vaccine was administered to 20 participants. They found significantly higher peak geometric mean titers for stalk antibodies in the LAIV H5N2 experienced group vs those who received only the inactivated H5N1 vaccine. In this study, the value of prime-boost vaccination for effectively inducing stalk antibodies was highlighted, which represents an attractive target for developing vaccines that induce stalk reactive antibodies.