Vaccinations

Describe active immunization:

• Process

• Priming dictates?

Active Immunization: Vaccination

• Process:

  • Deliberate exposure to Antigen that will not produce disease -> stimulate primary immune response

  • Memory cells produced

  • Rapid secondary response when pathogen encountered later

• Priming:

  • Dictates spacing of doses + timing

1. Define

   • Immunization

   • Immunogen

   • Antigen

2. Difference between Antigen/Immunogen?

3. What makes an antigen more immunogenic?

Definition:

• Immunization

  • Introduce Antigen -> deliberate induce adaptive immune response 

• Immunogen

  • molecule that elicits immune response by an organism’s immune system

• Antigen

  • molecule that can bind to product of immune response

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Difference between Antigen/Immunogen?

• an immunogen is always an antigen

• an antigen does not necessarily have to be an immunogen

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What makes an antigen more immunogenic?

• Non-self, size, complexity

1. What are the checklist for an effective vaccine

2. What is the difference between Live vs Subunit/Killed vaccines

3. Difference between Preventative vs Therapeutic strategies

Checklist for effective vaccine:

1. Low levels of side effects/toxicity; does not cause serious harm

2. Should protect against exposure to natural, wild forms of Pathogens

3. Stimulate B/T Cell Responses

4. Should have long term effects (memory)

5. Should not req. Numerous doses/boosters

6. Inexpensive, long shelf life, ez to administer

7. Be seen as non-self (foreign) and has Danger Signals

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Difference between Live vs Subunit/Killed vaccines

• Live: induce antibodies + effector T cells

• Subunit/Killed: induce antibody response

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Preventative vs Therapeutic

• Preventative:

  • Given prophylactically to prevent infection

• Therapeutic:

  • given after infection to reduce or arrest disease progression

1. Describe the common side effects of vaccines?

2. Describe adjuvant

   • Definition

   • Mech

Common Side Effects:

• Local rxn @ injection site

• Fever

• Allergies

NOTE: some experience rxn  to medium rather then the antigens

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Adjuvant:

• Definition:

  • Any substance that enhances immunogenicity of vaccine antigens mixed w/ it.

    • Most proteins are poorly immunogenic when administered alone 

• Mech:

  • Usually associated w/ T helper cell responses

What is a hapten?

small molecule that can only elicit an immune response if combined w/ a larger carrier

What is Herd Immunity? What is its relationship to RO?

Herd Immunity:

• What is it?

  • Collective immunity via mass immunization -> indirect protection on  nonimmune members

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Herd immunity and R0 (R-nought; basic reproductive rate)

• What is R0 

  • R-nought

  • Basic Reproductive Rate of a virus

• Relationship:

  • Level of immunity needed for herd immunity = proportional to RO

What are the four types of vaccines?

Four Types:

• Live attenuated microorganisms

• Killed/inactivated microorganisms 

  • (non-infectious vaccines)

• Subunit vaccines

• mRNA vaccines

Describe Live attenuated microorganisms

• How does it work?

• Drawback?

• Mech of Creation

• Examples

Describe Killed/inactivated microorganisms 

• How does it work?

• Drawback?

• Examples

Describe Subunit vaccines

• How does it work?

• Drawback?

• Examples

Live attenuated microorganisms

• How does it work?

  • Microbe = rendered avirulent -> replicate in recipient -> immune response

    • May be stronger then a Killed/inactivated virus

• Drawback:

  • Some safety issues

    • Possibility of reversal of weakened state -> wildtype

• Mech of creation:

  • Virus isolated from human -> virus is used to infect another species -> virus adapt to new species, loses ability to affect human -> new virus now = attenuated -> vaccine

• Ex:

  • Measles

  • Mumps

  • Rubella

  • Smallpox

  • BCG

  • oral polio

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Killed/inactivated microorganisms 

• How does it work?

  • Org. = Killed -> vaccine

• Drawback:

  • Usually req >1 doses -> strong response

  • Some needs boosters

• Examples:

  • Whole pertussis

  • Inactivated polio vaccine

  • Hepatitis A

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Subunit vaccines

• What is it?

  • Contains Purified components of microorganisms 

    • Toxoids 

      • inactivated toxins

    • recombinant antigens

      • parts of antigens expressed in different systems

    • polysaccharides conjugated to carrier proteins

• Drawback:

  • Usually needs repeated doses w/ adjuvant

• Examples:

  • Hepatitis B

  • Tetanus

  • Diphtheria

  • Hib

  • Acellular

  • pertussis

Describe Toxoid Vaccines:

• What/Why?

• Mech?

• Ex

Describe CONJUGATE VACCINES: 

• What/why?

• EX

Describe RECOMBINANT VECTOR VACCINES: 

• What is it?

Describe mRNA VACCINES: 

• Mech?

• Advantage?

• Ex

TOXOID VACCINES: 

• What/why?

  • Vaccine used w/ inactivated toxins when  bacterial toxin = illness’s main cause 

• Mech:

  • Toxins inactivated via formalin

    • formaldehyde + sterilized water

• Ex:

  • Tetanus and Diptheria toxoid.

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CONJUGATE VACCINES: 

• What/why

  • Surface Polysaccharides -> disguise antigens -> immune can’t recognize

  • Solution: linking to a protein

• Ex:

  • Hib  Vaccine

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RECOMBINANT VECTOR VACCINES: 

• What is it?

  • Uses attenuated virus/bacteria as vectors -> introduce microbial DNA to cells

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mRNA VACCINES: 

• Mech:

  • Delivers mRNA into host cells -> foreign protein translated -> trigger immune response

    • Delivery system: lipid nanoparticles, polymers, polypeptides, and virus replicon particles

• Advantage (compared to traditional):

  • Better speed of design/production

  • Better effectiveness

• EX:

  • Covid

Describe the 2026 epidermiology update for Measles

2026 Epidemiology Update

• Measles outbreaks continued in North America during 2025-2026.

• Most cases occurred in unvaccinated or under-vaccinated persons.

• Measles remains highly contagious (R0 12-18).

• Maintaining high MMR coverage is critical for herd immunity

Describe HPV:

• Causes?

• Different Variants/Effects

Describe the vaccine used:

• Name

• Type

• Contents?

• Newer version?

HPV

• Causes:

  • genital warts  + Cervical Cancer

• Different Varients/Effects:

  • HPV6, HPV 11: Genital Warts

  • HPV16, HPV18: 70% of all cervical Cancers

    • 16 = about 50%

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Vaccine:

• Name:  “Gardasil” (Merck)

• Type:

  • Virus like particle (VLP) non-infectious capsid like particle, 

    • no nucleic acids

• Contents:

  • L1 capsids of  HPV 6, 11, 16, 18

    • (produced in yeast -> assumes native conformation)

  • Alum (adjuvant)

• Newer version: Gardasil- 9

  • Protects against:

    • HPV 6, 11, 16, 18, 31, 33, 45, 52 and 58

1. Describe Whooping Couth

   • Caused by

   • Symptoms

   • Mech

2. Describe the vaccination

   • Name

   • Contents

   • Difference between the two

3. Describe the 2026 epidemiology

Whooping cough (pertussis)

• Caused by:

  • Bordetella pertussis (gram negative coccobacillus bacteria)

    • strict aerobe

    •  nutritionally fastidious (need complex media)

    • Very Sensitive to Env.

• Symptoms:

  • Intense, paroxysmal coughing 

    • Can lead to hemorrhages/vomiting

  • tracheitis + bronchitis

  • accumulation of mucus, cells, bacteria in airways

    • Can be so intense -> need tracheotomy 

  • Impaired mucociliary elevator 

• Mech:

  • Toxin -> sensitizes cough receptors -> easily triggered

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Vaccination

• Name: DtaP and Tdap

• Contains:

  • Pertussis toxoid (inactive)

  • FHA (filamentous hemagglutin)

  • pertactin (both adhesin)

  • fimbriae

• Difference between the two:

  • DTaP – infants and children < 7yo

  • Tdap – adolescents and adults

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NOTE:

Vaccines w/ 3-5 components are better than 1-2 components.

Adverse reactions are much lower with the acellular version

Adult booster recommended b/c major carriers

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Pertussis Epidemiology Update

• Cases rebounded after the COVID-19 pandemic.

• Activity remained elevated through 2024-2025.

• Waning immunity contributes to adolescent and adult transmission.

• Maternal Tdap vaccination remains important

Describe the Influenza virus

• Family

• Type/variations

• Reservoirs

Describe the clinical features

• incubation period

• symptoms

• complications

Describe the Vaccine:

• type

• Quad vs Trivalent

Influenza Virus

• Family: Orthomyxoviridae

• Type/variations:

  • - strand RNA virus

    • Type A (humans & other animals)

    • Type B (humans)

    • Type C (humans)

• Reservoirs 

  • Birds, pigs, horses, humans

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Clinical Features

• Incubation period: 

  • 1 to 4 days

• Symptoms: 

  • fever, 

  • chills, 

  • myalgia,

  • sore throat, 

  • cough, 

  • headache

  • Usually resolve in 1 week, cough may persist

• Complications: 

  • Bronchitis,

  • ear-ache,

  • sinusitis, 

  • bacterial pneumonia

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Vaccine:

• Type: 

  • Seasonal flu vaccines

    • Modified based on which strands are most prevalent @ the time

• Previous: Quadrivalent:

  • Protects against:

    • influenza A (H1N1) virus

    • influenza A (H3N2) virus

    • two influenza B viruses

• Now: Trivalent 

  • Protects against:

    • A (H1N1)

    • A(H3N2)

    • B:

      • B/ Yamagata 

      • B/Victoria

Describe the Rota Virus

• Symptoms

• Stats

• Outbreaks locations

• Death via?

Describe the Biological Characteristics

Describe the Vaccine:

• Name

• Freq

• Timing

• Route of admin

Rotavirus

• Symptoms:

  • intense diarrhea, 

    • often preceded by vomiting. 

  • Fever.

  • Symptoms: several days-week.

  • Adult symptoms = milder

• Stats:

  • Most common cause of infectious dirrhea <2 years of age

  •  50,000 hospitalizations/year 

• Outbreaks Location:

  • hospital nurseries 

  • day-care centers

• Death:

  • Via severe dehydration 

    • In dev. countries

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Biological characteristics:

• Reovirus family 

  • dsRNA genome

    • 11 segments

  • Icosahedral capsid

  • comprised of two layers

  • No envelope

  • Acid-resistant

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Vaccine:

• Name:

  • RotaTeq and Rotarix

• Frequency:

  • RotaTeq® (RV5)

    • 3 doses @  2 months, 4 months, and 6 months

  • Rotarix® (RV1)

    •  2 doses @ 2 months and 4 months

• Timing:

  •  first dose of both given before 15 weeks

  • All doses complete before 8 months old

• Route of Admin:

  • drops in child’s mouth

Describe the CDC Child & Adolescent Immunization Schedule: Key Updates

• Routine childhood vaccination remains the foundation of disease prevention.

• RSV prevention now includes maternal vaccination during pregnancy an infant monoclonal antibody protection strategies.

• MMR, DTaP, IPV, Varicella, HPV, MenACWY, and annual Influenza vaccines remain core recommendations.

• Catch-up vaccination should be performed whenever schedules are delayed.

• Vaccination decisions should always follow the current CDC child and adolescent schedule.

CDC Adult Immunization Schedule: Key Updates

• Annual influenza vaccination recommended for all eligible adults.

• RSV vaccination recommended for adults ≥75 years and selected adults 50- 74 years at increased risk.

• COVID-19 vaccination continues for eligible adults according to current CDC guidance.

• Shingrix remains recommended for prevention of herpes zoster.

• Tdap/Td booster recommended every 10 years

Important 2026 Vaccine Schedule Changes

• RSV vaccination is now a routine component of adult preventive care.

• Maternal RSV vaccination helps protect infants during the first months of life.

• Pneumococcal vaccination increasingly utilizes PCV20 and PCV21-based strategies.

• Trivalent influenza vaccines have replaced previous quadrivalent formulations.

• Risk-based vaccination is increasingly emphasized for immunocompromised and high-risk populations

2026-2027 Vaccine Updates

• RSV vaccination programs continue expanding.

• PCV20/PCV21 incorporated into adult schedules.

• Updated COVID-19 vaccines remain recommended for high-risk groups.

• Combination influenza/COVID vaccines are under development

List/Describe the Next-Generation Vaccine Platforms

• mRNA technology

  • expanding beyond COVID-19.

• Self-amplifying RNA (saRNA) _ circular RNA (circRNA)

  • improve durability

  • reduce dose requirements.

• Combination vaccines

  • Ex: (influenza + COVID-19)

  • Shows promising phase 3 immunogenicity and safety results

• AI-assisted antigen design is emerging as a vaccine-development tool