Vaccines

Introduction

Immunization allows for individuals to be protected against disease
Immunity can be conferred in two ways including
- active immunity that is maintained by the immune system
- passive immunity that is given transiently from outside
Vaccinations are a major source of conferring immunity outside normal infection and include
- viral vaccines divided into
  - killed vaccines
  - live attenuated vaccines
- bacterial vaccines
Often vaccinations require an adjuvent that
- enhances the immune reaction against the vaccine provided
- increases the development of memory to non inflammatory antigens
- can be of several types including
  - aluminum potassium sulfate
  - muramyl dipeptide
  - LPS/polyribonucleotides
Though vaccines are generally safe, contraindications to their use include
- people with egg allergies who should avoid
  - yellow fever vaccine and other vaccines made in eggs
- pregnant women who should avoid
  - rubella vaccines
- immunocompromised individuals who should avoid
all live vaccines

Active vs Passive Immunity

Differences Between Active and Passive Immunity
Feature	Passive	Active
Acquisition method	Receiving preformed antibodies	Exposure to infection or to foreign antigens
Examples	Maternal IgG crossing placentaBabies getting IgA in breast milkAdministration of antitoxin	Infection with the specific pathogenAdministration of a vaccine
Onset	Immediate upon administration	Slow to allow for development of full immune response
Duration	Very short with a half life between two weeks and four weeks	Long or even lifetimeDue to generation of memory

Viral Vaccines

Viral vaccines can either be live attenuated or killed with several notable differences

Differences Between Live and Killed Vaccines
Feature	Live	Killed
Production method	Design a nonpathogenic version of a virus that can still grow transiently in the host	Inactive pathogen or pathogen antigens by treatment with heat or chemicals
Pros	Induce both cellular and humoral responsesinduces lifelong immunity (usually)	Safer than live vaccines because they cannot revert to pathogenic state
Cons	Cannot give to immunocompromised patientsSmall chance of reverting to pathogenic state	Weaker response (usually only humoral)May require booster shots
Examples	Everything elseMMRVZVPolio (Sabin)Etc	Rest In Peace Always RabiesInfluenzaPolio (Salk)Hepatitis A

Bacterial Vaccination

Bacterial vaccination involves administration of characteristic protein which can be
- inactivated toxin produced by pathogen called a toxoid
- coat protein that surrounds the pathogen called a capsule
- other important proteins that are conserved by the pathogen
Select examples of vaccines against pathogenic bacteria include
- DTaP that is composed of
  - C. diptheriae toxoid
  - C. tetani toxoid
  - B. pertussis toxoid
- H. influenzae capsular type B
- S. pneumoniae that comes in two forms including
  - a pediatric version with
    - 7 capsule types
    - think: a 7 year old gets PCV
  - an adult version with
    - 23 capsular types
N. meningitidis with 4 capsular proteins