Vaccines & Immunizations:- Terms

Background

Let us list some of the terms you might possibly hear when vaccines and immunizations are being discussed.

Terms

 

Subject Term Description
Infection Symptom
Asymptomatic Infection The presence of infection without symptoms.

Also known as Asymptomatic infection, Subclinical Infection, and Inapparent infection.

Immune System Condition
Immunosuppression When the immune system is unable to protect the body from disease. This condition can be caused by disease (like HIV infection or cancer) or by certain drugs (like those used in chemotherapy). Individuals whose immune systems are compromised should not receive live, attenuated vaccines.
Types of Vaccines
Live-attenuated vaccines Live vaccines use a weakened (or attenuated) form of the germ that causes a disease.
Because these vaccines are so similar to the natural infection that they help prevent, they create a strong and long-lasting immune response. Just 1 or 2 doses of most live vaccines can give you a lifetime of protection against a germ and the disease it causes.Also known as attenuated vaccines.  Diseases that live vaccines have been used against include Measles, mumps, rubella (MMR combined vaccine), Rotavirus, Smallpox, Chickenpox, Yellow fever.
Inactivated vaccines Inactivated vaccines use the killed version of the germ that causes a disease.
Inactivated vaccines usually don’t provide immunity (protection) that’s as strong as live vaccines. So you may need several doses over time (booster shots) in order to get ongoing immunity against diseases.  Targeted infections include Hepatitis A, Flu, Polio, and Rabies.
Subunit, recombinant, polysaccharide, and conjugate vaccines Subunit, recombinant, polysaccharide, and conjugate vaccines use specific pieces of the germ — like its protein, sugar, or capsid (a casing around the germ).

Because these vaccines use only specific pieces of the germ, they give a very strong immune response that’s targeted to key parts of the germ. They can also be used on almost everyone who needs them, including people with weakened immune systems and long-term health problems.

Used to protect Hib (Haemophilus influenza type b), Hepatitis B, HPV (Human papillomavirus), Whooping cough (part of the DTaP combined vaccine), Pneumococcal disease, Meningococcal disease, Shingles.

Toxoid vaccines Toxoid vaccines use a toxin (harmful product) made by the germ that causes a disease. They create immunity to the parts of the germ that cause disease instead of the germ itself. That means the immune response is targeted to the toxin instead of the whole germ.

Like some other types of vaccines, you may need booster shots to get ongoing protection against diseases.

Toxoid vaccines are used to protect against Diphtheria and Tetanus.

DNA vaccines DNA vaccines are easy and inexpensive to make — and they produce strong long-term immunity.
Recombinant vector vaccines Recombinant vector vaccines (platform-based vaccines) act as natural infection, so they’re especially good at teaching the immune system how to fight germs.
Immunity Acquisition
Immunity Protection against a disease. There are two types of immunity, passive and active. Immunity is indicated by the presence of antibodies in the blood and can usually be determined with a laboratory test. See active and passive immunity.
Active Immunity The production of antibodies against a specific disease by the immune system. Active immunity can be acquired in two ways, either by contracting the disease or through vaccination.

Active immunity is usually permanent, meaning an individual is protected from the disease for the duration of their lives.

Passive immunity Protection against disease through antibodies produced by another human being or animal.

Passive immunity is effective, but protection is generally limited and diminishes over time (usually a few weeks or months).

For example, maternal antibodies are passed to the infant prior to birth. These antibodies temporarily protect the baby for the first 4-6 months of life.

Community immunity A situation in which a sufficient proportion of a population is immune to an infectious disease (through vaccination and/or prior illness) to make its spread from person to person unlikely. Even individuals not vaccinated (such as newborns and those with chronic illnesses) are offered some protection because the disease has little opportunity to spread within the community.

Also known as herd immunity.

Immunity Level
Waning Immunity The loss of protective antibodies over time.
Event
Adverse event A health problem that crops up in volunteers in a clinical trial of a vaccine or a drug. An adverse event isn’t always caused by the treatment tested in the trial.
Allergy
Allergy A condition in which the body has an exaggerated response to a substance (e.g. food or drug). Also known as hypersensitivity.
Hypersensitivity A condition in which the body has an exaggerated response to a substance (e.g. food or drug). Also known as an allergy.
Hyposensitivity A condition in which the body has a weakened or delayed reaction to a substance.
Measurement
Background rate How often a health problem, known as an adverse event, arises in the general population. To determine if a vaccine or a drug is safe, researchers compare the rate of adverse events in a trial to the background rate.
Efficacy A measurement of how effective treatment was in a clinical trial.

To test a coronavirus vaccine, for instance, researchers compare how many people in the vaccinated and placebo groups get Covid-19.

The real-world effectiveness of a vaccine may turn out to be different from its efficacy in a trial.

Phases
Phase 1 Phase 1 trials usually involve a few dozen people and are designed to observe whether a vaccine or drug is safe.
Phase 2 Phase 2 trials, involving hundreds of people, allow researchers to try out different doses, and gather more measurements about the vaccine’s effects on the immune system.
Phase 3 Phase 3 trials, involving thousands or tens of thousands of volunteers, determine the safety and efficacy of the vaccine or drug by waiting to see how many people are protected from the disease it’s designed to fight.
Stages
Preclinical research Studies that take place before the start of a clinical trial, typically involving experiments where treatment is tested on cells or in animals.
Post-market surveillance The monitoring takes place after a vaccine or drug has been approved and is regularly prescribed by doctors. This surveillance typically confirms that the treatment is safe. On rare occasions, it detects side effects in certain groups of people that were missed during clinical trials.
Protein
Antibody A protein found in the blood that is produced in response to foreign substances (e.g. bacteria or viruses) invading the body. Antibodies protect the body from disease by binding to these organisms and destroying them.
Immune globulin A protein found in the blood that fights infection. Also known as gamma globulin.
Impact within population
Epidemic The occurrence of disease within a specific geographical area or population that is in excess of what is normally expected.
Pandemic Protection against disease through antibodies produced by another human being or animal. Passive immunity is effective, but protection is generally limited and diminishes over time (usually a few weeks or months). For example, maternal antibodies are passed to the infant prior to birth. These antibodies temporarily protect the baby for the first 4-6 months of life.
Incidence The number of new disease cases reported in a population over a certain period of time.
Prevalence The number of disease cases (new and existing) within a population over a given time period.

 

References

  1. US Government
    • CDC
      • Vaccines and Immunizations
    •  HHS
      • Vaccines.gov
        • Type of Vaccines
          Link

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