Vaccines pdf Pt:2

What is a vaccine?

biological preparations made from living organisms or components that enhance immunity and prevent or treat disease. They mimic infection without causing illness.

Origin of the word "vaccine"

From Variolae vaccinae (cowpox), used by Edward Jenner in 1798 to prevent smallpox.

How are vaccines administered?

Usually liquid form via injection, oral, or intranasal routes.

Types of vaccine construction

Live-attenuated, inactivated, subunit/recombinant, toxoid, and conjugate vaccines.

Live-attenuated vaccine definition

Uses weakened microorganisms with reduced ability to cause disease.

Examples of live-attenuated vaccines

Measles, Mumps, Rubella, Varicella.

Inactivated vaccine definition

Uses whole organisms killed by chemical, thermal, or other methods.

Examples of inactivated vaccines

Hepatitis A, Influenza, Pneumococcal polysaccharide.

Subunit or recombinant vaccine definition

Uses purified antigenic components such as proteins or polysaccharides.

Example of subunit vaccine

Hepatitis B recombinant vaccine.

Toxoid vaccine definition

Uses inactivated toxins from toxin-producing bacteria.

Examples of toxoid vaccines

Tetanus and Diphtheria vaccines.

Conjugate vaccine definition

Polysaccharides linked to proteins to improve immune response in young children.

Examples of conjugate vaccines

Pneumococcal conjugate, Meningococcal conjugate, Hib conjugate.

Purpose of combination vaccines

To protect against multiple diseases with one shot; commonly used in childhood schedules.

What does a vaccine contain?

Antigens plus excipients including fluids, preservatives, additives, and sometimes adjuvants.

Purpose of preservatives in vaccines

Ensure sterility during shelf-life and prevent contamination in multi-dose vials.

Examples of preservatives used in vaccines

Phenol, benzethonium chloride, 2-phenoxyethanol, thimerosal.

What are vaccine adjuvants?

Substances that enhance immune response to vaccine antigens.

Most common vaccine adjuvant

Aluminum salts.

Examples of adjuvanted vaccines

Hepatitis A, Hepatitis B, DTaP/Tdap, Hib, HPV, pneumococcal conjugate, Japanese encephalitis.

How do vaccines work?

They introduce antigens that trigger antibody production and immune memory without causing disease.

What is an antigen?

A component of a pathogen that triggers an immune response.

What is an antibody?

A protein that binds to antigens and facilitates their destruction.

What is immune memory?

The immune system's ability to quickly respond to future exposures to the same pathogen.

Difference between natural infection and vaccination

Infection causes disease; vaccination induces immunity without illness.

What determines duration of vaccine protection?

Type of antigen and how it is processed by the immune system.

Why are polysaccharide vaccines less effective in infants?

Infant immune systems cannot form strong memory responses to polysaccharides.

Vaccine-preventable diseases

34+ diseases including smallpox, polio, measles, diphtheria, pertussis, tetanus, etc.

First vaccine-preventable disease

Smallpox.

Who pioneered the first vaccine?

Edward Jenner (smallpox, 1798).

Who advanced vaccine science after Jenner?

Louis Pasteur (rabies, anthrax, cholera vaccines).

What is vaccine efficacy?

Reduction in disease incidence in vaccinated vs. unvaccinated populations under controlled conditions.

What is vaccine effectiveness?

How well a vaccine prevents disease in real-world conditions.

Typical efficacy of licensed vaccines

70% to almost 100%.

Formula for vaccine efficacy

(Attack rate unvaccinated - Attack rate vaccinated) ÷ Attack rate unvaccinated × 100%.

Herd immunity definition

When high vaccination coverage prevents disease spread, protecting even unvaccinated individuals.

Diseases with high herd immunity thresholds

Measles (83-94%), Pertussis (92-94%).

What are AEFIs?

Adverse Events Following Immunization.

Most common vaccine reactions

Pain, redness, swelling, mild fever.

Rare vaccine reactions

Severe allergic reactions, encephalitis, or vaccine-associated paralytic polio (extremely rare).

AEFI frequency categories

Very common (>1/10), common (>1/100), uncommon (>1/1000), rare (>1/10,000), very rare (<1/10,000).

Purpose of VAERS in the US

A passive surveillance system to monitor vaccine safety and detect potential adverse events.

What is VSD (Vaccine Safety Datalink)?

A system linking vaccination histories with medical records to study vaccine safety.

Phases of vaccine clinical trials

Phase I: tens; Phase II: hundreds; Phase III: thousands.

Purpose of vaccine injury compensation systems

Provide no-fault compensation and protect vaccine supply reliability.

US vaccine injury compensation program name

National Vaccine Injury Compensation Program (VICP).