Table 2.

Types of Vaccines

Vaccine Type	Description	Immune Response Generated	Examples	Notes
Live attenuated	Weakened organism able to replicate in humans with reduced pathogenicity but retained immunogenicity	B and T call responses, induce immunological memory (memory B cells and long-lived plasma cells)	MMR, yellow fever, live attenuated influenza vaccine (LAIV), varicella	Contraindicated when CD4 < 200 or 15%. Avoid LAIV in PWH regardless of CD4
Live nonreplicating	Weakened organism unable to replicate in humans	B and T cell responses, induce immunological memory	Modified Vaccinia Ankara (Jynneos)	Safe in PWH regardless of CD4
Whole inactivated	Killed organism, unable to replicate or cause disease	B and T cell responses, induce immunological memory	Inactivated polio vaccine (IPV), HAV	May have higher reactogenicity
Subunit (multiple types)
- Polysaccharide	Purified bacterial capsular polysaccharides from inactivated organism	T-cell independent, generate exclusively antibody-dependent response and do not induce immunological memory	PPSV23	Limited immune memory
- Protein-polysaccharide conjugate	Purified polysaccharides from inactivated organism conjugated to a protein carrier	Engage T-cells and promote generation of memory B cells and long-lived plasma cells	PCV15/20/21, MenACWY	Common carrier proteins are tetanus toxoid, diphtheria toxoid (DT), CRM197 (non-toxic variant of DT)
- Purified protein	Purified protein from inactivated organism	B and T cell responses, induce immunological memory	Inactivated influenza vaccine	Often require adjuvants to enhance immune response
- Recombinant protein	Antigen produced through recombinant DNA technology	B and T cell responses, induce immunological memory	RZV (Shingrix), recombinant influenza vaccine (RIV), Heplisav-B	Often require adjuvants to enhance immune response
- Virus-like particle (VLP)	Recombinant capsid proteins that self-assemble as a shell to form VLPs	B and T cell responses, induce immunological memory	HPV, HBV (Engerix-B, Recom-bivax-HB)	Closely resemble viral structure, 9vHPV is highly immunogenic
- Outer membrane vesicle	Spherical buds made from the outer membrane of gram-negative bacteria that contain membrane surface proteins and lipids, vaccines typically also contain recombinant proteins	B and T cell responses, induce immunological memory	4CMenB (Bexsero)	Strong immunogenicity due to bacterial membrane components
Toxoid	Inactivated toxins	B and T cell responses, induce immunologic memory	Diphtheria, tetanus	Neutralizes toxins rather than bacteria itself
mRNA	mRNA encoding antigen proteins encased in lipid nanoparticles	B and T cell responses, induce immunologic memory	SARS-CoV-2, RSV (mResvia)	Rapidly adaptable platform

Adapted from Pollard AJ, Bijker EM, ‘A guide to vaccinology: from basic principles to new developments.’ Nat Rev Immunol. 2021;21(2):83–100[118]