Vaccines- Final Deora Lecture- Exam 4

Micro 4110 Exam 4

Definition of Vaccine

A product that stimulates a person’s immune system to produce immunity to a specific disease, protecting the person from that disease. Usually administered through needle injections but can also be administered by mouth or sprayed into nose

Rank of vaccination in terms of preventing disease

Second only to clean water.

How are vaccines used

As prophylactics, but not as therapeutics

Passive immunization

Introduction of antibodies to treat disease. Does not count as vaccination

Cost of vaccination

Much cheaper than the cost of treating diseases, as well as the societal savings (like parents losing money by taking off work to care for children)

Goals of vaccination

To generate long-lived memory to pathogenic antigens and to reduce length and severity of illness by eliminating the pathogen more efficiently

Vaccine characteristics

Can’t cause severe illness or death, minimal side effects, protects from illness, lasts several years, low cost, stable, easy to administer

Heterologous vaccine

Uses a closely related organism

Attenuated vaccine

Uses a weakened microorganism

Inactivated vaccine

Uses a killed microorganism

Toxoid vaccine

Uses an inactivated bacterial toxin

Subunit vaccine

Uses one or more antigens from an infectious agent

Conjugate vaccine

Uses a weakly immunogenic polysaccharide antigen attached to an immunogenic protein

Limitations of live attenuated vaccines

Reactogenic, possible reversion to active virus

Limitations of inactivated vaccines

Reactogenic

Limitations of subunit vaccines

Reduced efficacy compared to live attenuated and inactivated vaccines

Limitations of toxoid vaccines

Potentially reactogenic, single antigen

Contents of a subunit vaccine

Purified antigens and adjuvants to amplify immune responses

Adjuvant

A substance that amplifies the immune response, but isn’t immunogenic itself. It enhances the speed and duration of an immune response, and increases the immunogenicity of weak antigens. Stimulates production of antigen specific antibodies and T cells.

Practical benefits of subunit vaccines

Enhance immune response in immunologically immature patients, so a wider age range can receive them. Decreases the dose needed, so reduces costs.

Active immunization

Natural infection, or vaccines. Relatively long-lived and permanent.

Passive immunizaion

Passing of antibodies from another source, such as maternally, via anti-toxins or Igs, or monoclonal antibodies for COVID. Effectiveness is temporary. NOT a form of vaccination

How vaccines work

Induce active immunity, and immunological memory like a natural infection without causing disease. Immunological memory allows for rapid recognition of and response to infection.

Secondary immune responses

Much stronger than primary immune responses, and may be able to clear pathogens before any damage occurs. This is why boosters for vaccines are so important

How long after primary antigen exposure does it take for antibodies to be produced

Lag phase lasts 2-3 days or up to months, but during this time B cells are differentiating into plasma cells

Primary immune responses

Relatively low levels of antibodies, and over time the antibody levels will decline to undetectable levels. First antibody type is IgM, which provides short-term protection

Secondary immune responses

Accelerated as compared to primary, short lag phase due to memory cells. Antibodies produced at high levels, and are primarily IgG.

Memory cells

After elimination of 1st infection/antigen exposure, some B and T cells are converted to memory cells. On secondary exposure, these memory cells are able to quickly differentiate into effector cells.

Natural infection vs vaccination

Natural infection provides stronger immunity, but vaccinations are much safer for the person receiving them.

Whole cell pertussis vaccine (wPV)

An inactivated vaccine. Unknown number of antigens, Th1/17 T cell response, IgG2 isotype antibodies, long-lived protection, highly reactogenic.

Acellular pertussis vaccine (aPV)

Subunit vaccine. 3-5 antigens, Th1/2, Th2 skewed cell response, IgG1 isotype antibodies, short-lived protection, doesn’t clear bacteria from the nose and doesn’t prevent transmission.

Th1/17 T cell response

Allows for a highly protective response

IgG2 isotype antibodies

Highly opsonic antibodies

Th2 T cell response

Short lived protective response

Influenza vaccine

Live attenuated vaccine, given yearly because they are engineered against the currently circulating strain, as influenza viruses undergo antigenic variation and antibodies and T cells against one strain might not recognize another strain.

Next generation COVID vaccine goals

Develop a vaccine that use antigens that can elicit antibodies that can neutralize multiple COVID variants. Add additional antigens from COVID. Generate mucosal immunity so that vaccination can be administered via inhalation or orally.

Mosaic-8b

A next generation COVID vaccine, a Pan-sarbecovirus vaccine that incorporates RBDs from human COVID and 7 animal coronaviruses, inducing broader neutralizing antibodies in mice and nonhuman primates

Vaccine innovations

Flu shots that take guesswork out of targeting strains, one-dose vaccines that administer their own boosters, easier vaccines to administer, vaccines that contain immunizations against several diseases.