Introduction
The ongoing evolution of the SARS-CoV-2 virus and emerging variants have underscored the critical need for effective and adaptable COVID-19 vaccination strategies, especially in adolescents. PHH-1V is a novel bivalent protein-based COVID-19 vaccine, distinct from mRNA vaccines, which incorporates an adjuvant to enhance immune response. Previously evaluated in adults, PHH-1V demonstrated strong immunogenicity and a favorable safety profile as a booster dose. This study focused on assessing PHH-1V as a heterologous booster—that is, a booster different from the original vaccine series—in healthy adolescents previously vaccinated with the Pfizer-BioNTech mRNA vaccine (BNT162b2).
