- Induces an active immune response (humoral and/or cellular) to specific pathogens.
|Live attenuated vaccine||Microorganism loses its pathogenicity but retains capacity for transient growth within inoculated host.
Induces cellular and humoral (anti-body mediated) responses.
MMR and varicella vaccines can be given to HIV ⊕ patients without evidence of immunity if CD4 cell count ≥ 200 cells/mm3.
|Pros: induces strong, often lifelong immunity.
Cons: may revert to virulent form.
Often contraindicated in pregnancy and immunodeficiency.
|Adenovirus (nonattenuated, given to military recruits), Polio (sabin)
Varicella (chickenpox) (US)
“Attention! Please Vaccinate Small, Beautiful Young Infants with MMR Regularly!”
|Killed or inactivated vaccine||Pathogen is inactivated by heat or chemicals.
Maintaining epitope structure on surface antigens is important for immune response.
Mainly induces a humoral response.
|Pros: safer than live vaccines.
Cons: weaker immune response; booster shots usually required.
|Rabies, Influenza (injection), Polio (Salk), hepatitis A
SalK = Killed RIP Always
|Subunit||Includes only the antigens that best stimulate the immune system.||Pros: lower chance of adverse reactions.
Cons: expensive, weaker immune response.
|HBV (antigen = HBsAg) (US)
HPV (types 6, 11, 16, and 18), (US)
Acellular pertussis (aP) (US)
Neisseria meningitidis (various strains) (US)
Streptococcus pneumoniae (US)
Haemophilus influenzae type b (US)
|Toxoid||Denatured bacterial toxin with an intact receptor binding site. Stimulates the immune system to make antibodies without potential for causing disease.||Pros: protects against the bacterial toxins.
Cons: antitoxin levels decrease with time, may require a booster.
|Clostridium tetani (Tetanus toxoid, DTaP)
Corynebacterium diphtheriae (protein carrier in conjugated vaccines, allows polysaccharide antigen to be displayed on MHC of APCs.)