Ad26.RSV.FA2

Ad26.RSV.FA2 is an investigational vaccine candidate for the prevention of respiratory syncytial virus (RSV) infection. It is based on a replication-incompetent adenovirus serotype 26 (Ad26) vector that encodes the fusion (F) protein from the RSV A2 strain. The F protein in this construct is in its wild-type form, not stabilized in the prefusion conformation. Preclinical and early clinical studies have shown that Ad26.RSV.FA2 induces robust, Th1-biased immune responses characterized by both humoral and cellular immunity, including durable antibody production and T-cell responses against RSV F protein. The vaccine has been evaluated as both a prime and boost component in various regimens, often compared to or combined with other adenoviral vectors such as Ad35.RSV.FA2[1][5][6]. Development efforts have focused on optimizing immunogenicity and safety for use in populations at risk of severe RSV disease, such as infants and older adults.