Live-attenuated viral vaccine (LAV)

A live-attenuated viral vaccine (LAV) is a biological preparation that uses a weakened form of a virus to induce protective immunity. Unlike subunit or inactivated vaccines, LAVs undergo limited replication within the host, which provides a prolonged and diverse antigenic stimulus that closely mimics a natural infection (NIH, 2019). This process typically results in robust, long-term immunity, often requiring fewer doses than other vaccine types to achieve lifelong protection (CDC, 2021). However, because the vaccine contains a live agent, it poses risks for individuals with weakened immune systems and carries a theoretical risk of the virus mutating back to a more virulent form, known as reversion (WHO, 2020). Notable examples of this modality include the vaccines for measles, mumps, rubella, varicella, and yellow fever (PubMed, 2022). In drug databases, this entry often serves as a placeholder for vaccines that do not interact with a single discrete molecular target but rather engage the entire immune system.

Other names

Attenuated virusWeakened viral vaccineLive-attenuated vaccineLAV

Live-attenuated vaccines work by introducing a weakened version of a virus into the body, which replicates sufficiently to stimulate a comprehensive immune response—including both humoral (antibody) and cell-mediated (T-cell) immunity—without causing the full-blown disease in healthy individuals (StatPearls, 2023; CDC, 2021).