Practice question

Whole microbe vaccines contain complete intact microorganism either living attenuated with reduced virulence but replicating or killed inactivated retaining structural integrity but replication abolished. Examples live BCG, measles MMR, oral polio, live influenza cold adapted; killed whole cell pertussis, inactivated polio IPV, rabies, influenza whole virion. Subunit vaccines diverge by containing only specific antigenic components rather than entire organism, thereby not considered whole microbe. They include purified capsular polysaccharides, polysaccharide-protein conjugates, acellular pertussis proteins pertussis toxin, filamentous hemagglutinin, pertactin, recombinant hepatitis B surface antigen self-assembling virus like particles produced in yeast, split influenza HA NA subunits after detergent disruption, recombinant spike protein nanoparticles. Subunit vaccines offer improved safety unable to revert to virulence, lower reactogenicity due to removal of toxic components like lipopolysaccharide, defined composition permitting standardization, but often less immunogenic requiring adjuvants and booster schedules to compensate for lack of innate stimuli provided by whole microbe pathogen associated molecular patterns. Thus subunit is distinct category, excluded from whole microbe classification.