Classes of Vaccines

Live attenuated

Weakened strain of whole pathogen

Advantages:

• Cellular and humoral immunity

• Long-lasting immunity

Disadvantages

• Difficult to store and transport

• Risk of infection in immunocompromised patients

Inactivated

Whole pathogen killed or inactivated with heat chemicals, or radiation.

Advantages:

• transmission to contacts

• Ease of storage and transport

• No risk of severe active infection

Disadvantages:

• Risk of reversion

• Weaker immunity (humoral only)

• Higher doses and more boosters required

Subunit

Immunogenic antigens

Advantages:

• Lower risk of side effects

Disadvantages:

• Limited longevity

• Multiple doses required

• No protection against antigenic variation

Toxoid

Inactivated bacterial toxin

Advantages:

• Humoral immunity to neutralize toxin

Disadvantages:

• Does not prevent infection

Conjugate

Capsule polysaccharide conjugated to protein.

Advantages:

• T-dependent response to capsule

• Better response in young children

Disadvantages:

• Costly to produce

• No protection against antigenic variation

• May interfere with other vaccines.