Contact with infectious agents such as bacteria or viruses in a manner that promotes transmission and increases the likelihood of disease.


To predict by projecting past experience or known data.

Equivalence Trial

A type of trial for establishing identical effects of the therapies being compared.

Eradication campaign

The reduction of the prevalence of an infectious disease in the global host population to zero. Two infectious diseases have successfully been eradicated: smallpox in humans, and rinderpest in ruminants. There are four ongoing programs, targeting the human diseases poliomyelitis (polio), yaws, dracunculiasis (Guinea worm), and malaria.

Erythema Multiforme

A medical condition characterized by inflammation of the skin or mucous membranes (including the mouth, throat, and eyes). Erythema Multiforme has been reported following several infections (eg., Mycoplasma, HSV). Symptoms persist anywhere from 2 days to 4 weeks and include skin lesions, blisters, itching, fatigue, joint pain, and fever.

Essential Document

Documents which individually and collectively permit evaluation of the conduct of a trial and the quality of the data produced.

Essential medicine

Medicines that satisfy the priority health care needs of the population.

Essential Programme on Immunization (EPI) vaccine

A World Health Organization (WHO) program with the goal to make life-saving vaccines available to all children in all countries including Bacillus Calmette-Guérin (BCG), diphtheria, pertussis, tetanus, Haemophilus influenzae type B (Hib), Hepatitis B (HepB), polio, measles, rubella, pneumococcal disease (PNC), rotavirus (Rota), human papillomavirus (HPV), and COVID-19 (for adults).

Ethnic Factor

Factors relating to races or large populations grouped according to common traits and customs.

Eukaryotic cell

Cells that have a membrane-bound nucleus. All animals, plants, fungi, and many unicellular organisms are eukaryotes.


The cause or origin of disease.

European Medicines Agency (EMA)

Decentralised agency of the European Union (EU) responsible for the scientific evaluation, supervision and safety monitoring of medicines in the EU.

Expiry Date

The time period during which the product is known to remain stable, which means it retains its strength, quality, and purity when it is stored according to its labeled storage conditions.


An inactive substance that serves as the vehicle or medium for a drug or other active substance.

Exclusion Criteria

Characteristics that disqualify prospective subjects from inclusion in the study.

Expert Committee on Biological Standardization (ECBS)

WHO committee which provides recommendations and guidelines for the manufacturing, licensing, and control of blood products and related in vitro diagnostic tests, biotechnology products and vaccines along with the establishment of WHO Biological Reference Material.

Exploratory Trial

Phase I/II clinical trials to investigate the therapeutic intervention’s effects.


Percentage reduction of disease cases in a vaccinated group of people compared to an unvaccinated group. A vaccine’s efficacy is measured in a controlled clinical trial.

Efficacy rate

A measure used to describe how effective a vaccine is at preventing disease.


The occurrence of disease within a specific geographical area or population in excess of what is normally expected.


An animal that is developing either in its mother’s womb or in an egg.


Percentage reduction of disease cases in a vaccinated group of people compared to an unvaccinated group. Vaccine effectiveness is a measure of how well vaccines work in the real world.


A formulation with an edible outer packaging made from gelatin or other suitable material.

Effervescent Tablet

A refinement that, upon contact with water or another liquid, breaks apart to generate carbon dioxide.


The scientific study of diseases and how they are found, spread, and controlled in groups of people.


A general term describing brain dysfunction. Examples include encephalitis, meningitis, seizures, and the effects of head trauma.


The part of a foreign protein, or antigen molecule, that is capable of stimulating an immune response.


A disease that is Regularly occurring within a certain geographic area or in a certain group of people.

Epitope mapping

The process of experimentally identifying the binding site, or epitope, of an antibody on its target antigen (usually, on a protein).


A toxic heat-stable lipopolysaccharide substance present in the outer membrane of gram-negative bacteria that is released from the cell upon lysis.


The process of enhancing and augmenting raw data with additional information to improve data processing and analytics.

Enteric Coated Tablet

One that is designed to temporarily withstand attack by stomach acid, so that it does not dissolve in the stomach but allows release of the medication in the intestine.

Environmental Monitoring Program

A documented program describing routine monitoring of particles and microorganisms in process and manufacturing areas, including corrective actions.

Environmentally Friendly Process

The specific actions that allow reducing the environmental impacts among all the processes involved in the manufacture activities of a product.

Effect size

A quantitative measure of the magnitude of the experimental effect, which reflects practical significance of a research outcome.


Any of a group of chemical substances that are produced by living cells and cause particular chemical reactions to happen while not being changed themselves.

Effective Dose 50 (ED50)

Dose of a medication that produces a specific effect in 50% of the population that has been administered that dose.

Enzyme-Linked Immunosorbent Assay (ELISA)

A commonly used analytical biochemistry assay. The assay is a solid-phase type of enzyme immunoassay (EIA) to detect the presence of a ligand (commonly a protein) in a liquid sample using antibodies directed against the ligand to be measured.