VIRAL VACCINES AND ITS IMMUNIZATION SCHEDULE

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•       Active immunization –when an immune response is stimulated because of challenge with an immunogen, such as exposure to an infectious agent.

•       Ex: Vaccines, antigens, pathogenic microorganism

•       Passive Immunization – injection of purified antibody or antibody-containing serum to provide rapid, temporary protection or treatment of a person is termed passive immunization.

•       Mother to baby through feeding, Ab injection

Types of Vaccines:

a.    Inactivated vaccines

b.    Live-attenuated vaccines

c.    Messenger RNA (mRNA) vaccines

d.    Subunit, recombinant, polysaccharide, and conjugate vaccines

e.    Toxoid vaccines

f.     Viral vector vaccines

a. Inactivated vaccines – killed particles

§  Ex: Hepatitis A, Flu, Polio (Salk), Rabies.

§  Produced by chemical (e.g., formalin) or heat inactivation.

§  Inactivated vaccines usually generate antibody (TH2 responses)

§  Administered with an adjuvant.

b. Live attenuated vaccines

§  Live vaccines use a weakened (or attenuated) form of the germ that causes a disease.

§  create a strong and long-lasting immune response.

§  Just 1 or 2 doses provides lifetime immunity.

§  Enveloped viruses

o   Measles, mumps, rubella (MMR)

o   Rotavirus

o   Smallpox

o   Chickenpox

o   Yellow fever

 

c. Hybrid vaccines

§  Genes agents that cannot be properly attenuated can be inserted into safe viruses to form hybrid virus vaccines.

§  Eg., vaccinia, canarypox, attenuated adenovirus.

d. Subunit and Conjugate Vaccines

§  Both contain only pieces of the pathogens they protect against.

§  Isolating a specific protein from a pathogen and presenting it as an antigen on its own.

§  The acellular pertussis vaccine and influenza vaccine.

§  Another type is via genetic engineering.

§  A gene coding for a vaccine protein is inserted into another virus, or into producer cells in culture.

§  When the carrier virus reproduces, or when the producer cell metabolizes, the vaccine protein is also created.

§  The end result of this approach is a recombinant vaccine: the immune system will recognize the expressed protein and provide future protection against the target virus.

§  The Hepatitis B and human papillomavirus (HPV) vaccine

e. mRNA vaccines

§  COVID-19 vaccines.

§  mRNA vaccines make proteins in order to trigger an immune response.

§  Benefits including shorter manufacturing times

Because they do not contain a live virus, no risk of causing disease in the person getting vaccinated.

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