Week 9: Vaccines & Immunizations

Prevention and control strategy (3)

• host prevention

  • Immunity via immunization

  • behavioral change

  • improvement in general health (nutrition + exercise)

  • treatment (contacts + carriers)

• Environmental control

  • personal hygiene

  • food protection

  • water supplies

  • sanitation and regulation

• vector control

  • mosquitos and insecticides

  • animal pop control

passive immunization

• transfer of ab from those who are immune

• short

• immediate protection

• ex. maternal ab (natural) or HBIG (artificially acquired)

Active immunity

Vaccines

req for a good vaccine (6)

• produce good humoral, cellular, and or local immune response similar to natural infection

• produce protection against clinical disease and reinfection

• give protection for years - lifetime

• result in minimal side reactions or mild disese w/o delayed effects

• simple administration

• cost/benefit > cost/risk of natural disease & adverse risks of immunizations

Types of licensed vaccines

• live/attenuated

• killed

• toxoids

• conjugate

• active components

  • purified

  • subunit

  • recombinant

• viral vector, attenuated, recombinant

• nucleic acid

Live-attenuated vaccines

• live bacteria or viruses that infect but don’t cause disease

  • ex. MMR and Oral Polio

Killed whole vaccines

inactivated cells or viruses (can’t mult, infect, or cause disease)

ex. Injected polio and Hepatitis A

Toxoid

inactivated bacteria toxin (small molecule or protein)

ex. Tetanus and Diphtheria

Conjugate vaccines

• subunit Ag conjugated to an unrelated protein

  • ex. hemophilus influenzae and staph aureus

what is the advantage of using conjugate vaccines?

• B cell process vaccine and present protein Ag to Th

• convert a TI vaccine to TD vaccine

• much more effective for polysaccharide Ag

Subunit vaccines

immunogenic protein or other Ag only

ex. acellular pertussis and purified HBsAg for Hep B

Pros and cons for subunit vaccines

• Pros

  • can’t cause the disease

  • can’t eliminate endotoxin or undesirable components

• Cons

  • similar to killed-whole

  • purification can be expensive & difficult

  • a single Ag may not be effective as whole organism

Recombinant vaccines

subunit vaccine produced by genetic engineering

• purification can be cheaper and easier

• can use genes from viruses that can can’t be cultured

• ex. HBsAg for Hep B

Engineered live-attenuated vaccines

“vector” virus altered to carry Ag from another pathogen

ex. SARS-CoV-2 and VSV for EbolaV

Pros and cons of Engineered live-attenuated vaccines

Pros

• similar to live attenuated

• greatly reduced change of causing disease

• much easier to obtain usable live virus

Disadvantage

• live genetically engineered organisms face regulation issues

• could be difficult to engineer for proper expression

• Ag protein may not also target to correct issue

• Vaccinia can cause rare but severe illness

Nucleic acids (DNA or RNA) vaccines

genetically engineered DNA (as a plasmid) or RNA (as mRNA) which cells uptake and transform into a protein

ex. SARS-CoV-2

Pros and cons of Nucleic acids (DNA or RNA) vaccines

Pros

• can induce CMI as well as humoral immunity

• could use any gene standardization process

• faster, easier, cheaper, more stable than traditional subunit vaccine

Cons

• delivery methods must be worked out

• regulatory issues

• concern about auto-immunity (anti-DNA Ab) or integration to host DNA

What is considered a new era of vaccinology?

mRNA vaccine

Vaccine Adjuvants

substance that acts to accelerate, prolong, or enhance antigen-specific immune response when used as part of vaccine formulation

• most activate early innate immunity

Characteristics affecting immune response

Administration

• immunomodulator

• route (oral, injection, etc)

• injection site and needle size

• dose and schedule

Host

• age

• weight

• genetics

• smoking status

• nutrition and immune status

• interference by other infections or maternal ab

barriers to immunization

• cost of vaccine/insurance policies

• disease risk perception

• vaccine risk perception

• religious/philosophical objections

• complexity of schedule

• missed opportunities

• follow up difficulties

• hard to reach populations

• cold chain req

Vaccine concerns and hesitancy issues

• safety

• autism

• overwhelming the immune sys

• natural immunity superior

• disease don’t exist anymore

• big pharma conspiracy

• individual rights vs ph needs

Key challenges (4)

limited resources

competitive health priorities

poor management

inadequate monitoring/supervision