As the pandemic has developed, we have all had to grapple with words and terminology that many will have found confusing. Here is a list of those we had to have explained to us.


Acellular vaccine: A vaccine containing partial cellular material as opposed to complete cells.


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.


Adjuvant: A vaccine component distinct from the antigen that enhances the immune response to the antigen.


Allergy: A condition in which the body has an exaggerated response to a substance (e.g. food or drug). Also known as hypersensitivity.


Antibiotic: A substance that fights bacteria.


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.

Antigens: Foreign substances (e.g. bacteria or viruses) in the body that are capable of causing disease. The presence of antigens in the body triggers an immune response, usually the production of antibodies.

Antiviral: Literally “against-virus” — any medicine capable of destroying or weakening a virus.


Attenuated vaccine: A vaccine in which live microbes are weakened (attenuated) through chemical or physical processes in order to produce an immune response without causing the severe effects of the disease. Attenuated vaccines currently licensed in the United States include measles, mumps, rubella, varicella, rotavirus, yellow fever, smallpox, and some formulations of influenza, and typhoid vaccines.


Asymptomatic:  When you do not have the symptoms of the virus. 


Booster shots: Additional doses of a vaccine needed periodically to “boost” the immune system. For example, the tetanus and diphtheria (Td) vaccine which is recommended for adults every ten years.


Chronic health condition: A health related state that lasts for a long period of time (e.g. cancer, asthma).

Combination vaccine: A product containing components that can be divided equally into independently available routine vaccines.

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.


Conjugate vaccine: The joining together of two compounds (usually a protein and polysaccharide) to increase a vaccine’s effectiveness.


Cold Chain storage: One of the new vaccine candidates needs to be kept very cold in transit, minus 70 degrees celsius,  this means that specialist freezing equipment will be needed for the distribution of the vaccine. 


Efficacy rate: A measure used to describe how good a vaccine is at preventing disease.


Immune system: The complex system in the body responsible for fighting disease. Its primary function is to identify foreign substances in the body (bacteria, viruses, fungi or parasites) and develop a defense against them. This defense is known as the immune response. It involves production of protein molecules called antibodies to eliminate foreign organisms that invade the body.


Herd immunity: is a form of indirect protection from infectious disease that occurs when a sufficient percentage of a population has become immune to an infection, whether through vaccination or previous infections, thereby reducing the likelihood of infection for individuals who lack immunity.


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. 


Immunization: The process of being made immune or resistant to an infectious disease, typically by the administration of a vaccine. It implies that you have had an immune response.


Infectious: Capable of spreading disease. Also known as communicable.

Infectious agents: Organisms capable of spreading disease (e.g. bacteria or viruses).

Live vaccine: A vaccine in which live virus is weakened (attenuated) through chemical or physical processes in order to produce an immune response without causing the severe effects of the disease. Live vaccines currently licensed in the United States include measles, mumps, rubella, varicella, rotavirus, yellow fever, smallpox, and some formulations of influenza, shingles, and typhoid vaccines.  Also known as an attenuated vaccine.


Microbes: Tiny organisms (including viruses and bacteria) that can only be seen with a microscope.


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.


Polysaccharide vaccines: Vaccines that are composed of long chains of sugar molecules that resemble the surface of certain types of bacteria. Polysaccharide vaccines are available for pneumococcal disease.


Potency: A measure of strength.


Prevalence: The number of disease cases (new and existing) within a population over a given time period.

Quarantine: The isolation of a person or animal who is suspected of having a disease in order to prevent further spread of the disease


R Number: the rate of which one person infects another person, for every 1 person how many people do they impact.


Side Effect: Undesirable reaction resulting from immunization.

Susceptible: Unprotected against disease.

Sero-positive individuals: those people already with the antibodies and tracked by  


Vaccination: The physical act of administering any vaccine 


Vaccine: A suspension of live (usually attenuated) or inactivated microorganisms (e.g. bacteria or viruses) or fractions thereof administered to induce immunity and prevent infectious diseases and their sequelae. Some vaccines contain highly defined antigens (e.g., the polysaccharide of Haemophilus influenzae type b or the surface antigen of hepatitis B); others have antigens that are complex or incompletely defined (e.g. Bordetella pertussis antigens or live attenuated viruses).


Virus: A tiny organism that multiplies within cells and causes disease such as chickenpox, measles, mumps, rubella, pertussis and hepatitis. Viruses are not affected by antibiotics, the drugs used to kill bacteria.


Waning Immunity: The loss of protective antibodies over time.