Proteins found on the surface of pathogens such as viruses and bacteria. Antigens are unique to each pathogen. The body recognises an antigen on the SARS-CoV-2 virus as foreign and this stimulates an immune response.

Occurs when small changes in the pathogen’s genetic material accumulate, so that its antigens become slightly different from their original version. It is a common phenomenon in RNA (defined below) viruses such as SARS-CoV-2.

When a virus is present in the body without causing any harm to the person infected, who is asymptomatic or pre-symptomatic.
Coronaviruses – a family of viruses that cause respiratory and gastrointestinal illnesses in people.

Deoxyribonucleic acid, a molecule that carries genetic information.

Messenger RNA, the ‘ready-to-read’ instructions to produce proteins.

A term used to describe how an organism’s genetic material can change. Viral mutations are very common.

When a virus makes several copies of itself.

Organism or environment where a virus typically lives and reproduces.

Ribonucleic acid. A molecule with some similarities to DNA. Its main role is in decoding genetic material to make proteins. In some viruses, RNA carries the genetic code instead of DNA. SARS-CoV-2 is an RNA virus. There are different types of RNA, including messenger RNA (mRNA) and self-amplifying RNA.

These are club-shaped structural features that are found on the surface of the SARS-CoV-2 virus. It is the part of the virus that attaches to human cells so the virus can enter and infect them. This protein is a therapeutic target for antivirals; drugs that can interfere in the interaction between the spike protein and the human cells could stop the virus from entering cells and replicating. The spike protein is also central to some COVID-19 vaccines in development. It is an antigen recognised by the body and stimulates an immune response, including the production of antibodies that can neutralise the virus.

As a virus replicates, it can accumulate mutations. A version of the virus with these mutations is called a ‘variant’. Emergence of variants is a natural phenomenon. Most mutations have very little impact on the virus’s properties, others facilitate transmission or infection of other species. See also antigenic drift.

The scientific and medical discipline concerned with understanding the biology of viruses and viral diseases, their treatment and prevention. Virologists study common infections such as influenza and chickenpox to new and emerging viruses that cause Ebola, Zika and COVID-19.

This is often used to describe both accuracy and reliability of a test. For COVID-19 this would mean how good a test is at confirming the presence or absence of an active or previous COVID-19 infection. No diagnostic test or antibody test is 100% accurate.

Detects antibodies to SARS-CoV-2 virus from a current or previous infection.

Detects viral material indicating a current infection. Tests for COVID-19 detect whether viral antigens found on the surface of SARS-CoV-2 are present in a sample.

The proportion of people with symptoms that die.

Identifying the source and contacts linked to a confirmed case of an infectious disease. Contacts can be classified as high risk, low risk or no risk and given advice on what to do. This approach is used as a public health measure to contain the spread of an infection. Forwards contact tracing refers to finding the people that the person who tested positive could have passed the virus to. Backwards contact tracing refers to finding the individual who gave the virus to the person who subsequently tested positive.

A test that can confirm if someone has an active SARS-CoV-2 infection.

The study of what is causing a certain health outcome (diseases, environmental exposures, injuries), the distribution of diseases in different groups in the population, what causes them and changes over time. Knowledge from epidemiological research is used to design measures to control infectious disease.

Sometimes called excess deaths, this is the number of additional deaths in a time period that is a higher than would usually be expected. For example, if there were normally 500 deaths in 1 week, but 750 were reported, this would equal 250 excess deaths. At the time of writing there have been 63,401 excess deaths in England since 20 March 2020.

An incorrect result. For example, when someone with a SARS-CoV-2 infection tests negative.

The proportion of infected people that die.

Documentation that indicates an individual’s immune status. For COVID-19 this could be based on whether someone has been immunised or has antibodies because of a previous infection. There is insufficient evidence about the effectiveness of immunity passports. This is because having SARS-CoV-2 antibodies does not necessarily mean that someone is protected against a second infection. The duration of immunity following vaccination is also unclear.

The number of new cases of a disease in a population during a particular time period. Calculating incidence rates can indicate how quickly an infectious disease is occurring in a population.

The patient in an outbreak of a disease who is first identified by health authorities.

A scientific technique to detect and increase the amount of viral genetic material. Equipment using LAMP technology can be sited near to the person being tested and can give results in minutes instead of having to send samples for laboratory processing.

A type of molecular test to detect an active infection. The tests contain antibodies that bind to proteins (antigens) on the surface of the virus if it is present in a sample. A positive result is seen as a dark band or a fluorescent glow on the test kit, usually within minutes.

Using tests in a large sample of asymptomatic people to detect those who are currently infected.

A test that detects viral genetic material through PCR or newer laboratory techniques.

A term used to describe illness, injury or disability. Comorbidity or multimorbidity are sometimes used and refer to when someone has more than one condition at the same time.

Non-drug measures to limit the transmission of an infectious disease. These can be measures at the individual level such as physical distancing, the use of face masks and coverings, and improved hygiene measures. They can also be measures to constrain activities, such as the closures of various premises including sporting venues, pubs or shops.

A specialised laboratory method used to increase the amount of DNA or RNA in a sample so there is enough to test it. PCR tests are used to detect RNA in samples from people to see if the samples contain SARS-CoV-2 virus.

A diagnostic test performed at or near to the person by a trained operator (like a urine dipstick to check for urinary tract infections).

A measurement that expresses the proportion of people who have a disease at or during a given time period. Prevalence rates for disease are calculated by dividing the number of cases by the total number of people in the sample. They can be expressed as percentages or as cases per 100,000 people. It is often used alongside incidence, but they mean different things. While incidence counts only new cases in a given time period, prevalence counts both existing and new cases.

The person who brings an infectious disease into a group of people, such as a country, city or workplace.

A measure of how a disease spreads. The R number is the average number of people that one infected person will pass the virus onto. If R is more than 1 then an infection will spread in a population. Without any measures, the R for SARS-CoV-2 is 3.

A test that uses a saliva sample.

Describes when a person takes their own sample that is then sent elsewhere for processing and interpretation of results.

How well a test reports a positive result for people who have COVID-19.

How well a test reports a negative result for people who do not have COVID-19.

A type of self-sampling that uses a technique to take samples from the nose and throat for testing.

A small group of healthy people (<100) is given the vaccine to make sure there are no safety concerns, to see how well it stimulates an immune response and to work out an effective dose.

The vaccine is tested in a larger group (several hundred people) to see whether the vaccine works consistently, to assess the immune response and to look for side effects.

The vaccine is studied on a much larger scale (several thousand people) under natural disease conditions. This produces enough data to identify rare side effects and to evaluate how well the vaccine works in the real world; does it generate enough immunity to prevent and reduce di

When discussing a drug such as a treatment for COVID-19 or a COVID-19 vaccine, this refers to how well the drug achieves the intended effect when it is used in real world settings. For example, while a therapeutic may reduce 90% of the disease (see efficacy) in a research study involving healthy young people under strict research conditions, this may not be achieved when it is used in a wider population of people with different characteristics, such as older people or those with underlying health conditions.

The extent to which a drug works as intended when it is tested in ideal circumstances such as in controlled research study. For example, a COVID-19 vaccine may have 90% efficacy at preventing the disease. This means that cases of the disease were reduced by 90% in vaccinated vs. non-vaccinated people in the study.

Study where a pathogen is carefully given in controlled settings to healthy volunteers, who are therefore ‘challenged’ by it. These studies aim to better understand the infection process and find how to prevent and treat it.

Therapies based on antibodies against SARS-CoV-2 that can be used to treat COVID-19 patients.

Drugs used to prevent or treat viral infections. Some antivirals work by stopping the virus from entering cells while others inhibit stages of the viral life cycle, such as stopping the virus from replicating. Several antiviral drugs to treat COVID-19 are being evaluated but none has shown any significant clinical benefits so far in trials.

A steroid drug used to treat a range of inflammatory and allergic disorders. In hospitalised COVID-19 patients, it reduces deaths of ventilated patients by 35% and reduces deaths of patients requiring oxygen by 20%.

This is the minimum standard that drug manufacturers must meet in the production process. This is to ensure that drugs are of consistent high quality across batches and that they meet the requirements specified by regulators in a drug’s marketing authorisation.

Detecting, collecting and monitoring data about adverse events that may be linked to a medicine (such as a new drug or vaccine) so that appropriate action can be taken.

Positioning hospitalised COVID-19 patients on their stomachs. Research suggests that this benefits them because it improves oxygenation in the body.

Immune response developed naturally by the body following the first encounter with a new pathogen. After a certain time, the body will start to produce antibodies able to specifically recognise the new pathogen.

See live-attenuated vaccine.

Type of white blood cell that produces antibodies. Naïve B cells are immature B cells not yet exposed to a pathogen. Once exposed, they can become memory B cells, able to secrete antibodies against that specific pathogen.

Refers to the supply chain of some drugs and vaccines, which need to be in temperature-controlled environments, from production to delivery.

Chemicals signalling the presence of a pathogen in the body. They are part of the innate immune system and cause inflammation.

Vaccines where DNA instructions to build a pathogen’s protein are directly injected into the recipient. The US-based Inovio candidate or the Korean Genexine candidate use this strategy.

When enough individuals in a population are immune to an infection so that those who are not immune are protected as well. It is also known as ‘population immunity’.

Response developed by the body when infected by a pathogen. Primary immune response is the first response triggered by exposure to a pathogen. Immature (naïve) B cells are stimulated by antigens, become activated, and start producing antibodies that stick to these antigens. There will be an initial surge of antibodies and then, with time, these antibody levels will decrease as the infection is cleared. Secondary immune response occurs during second and subsequent exposures to the same pathogen. Memory B cells are able to recognise the antigens that they have been previously exposed to and start producing antibodies in higher quantities than during the primary response.

Immunity that is acquired when a person becomes infected by a pathogen and develops an immune response against it (see Active immune response and immune response).

Antibodies able to bind and stop the virus.

Contain a protein found on the surface of a pathogen that is used to trigger the immune response. This strategy is used by the GSK / Sanofi Pasteur candidate.

RNA able to create several copies of themselves before being read to make proteins. The Imperial College vaccine candidate uses this technology.

Protecting individuals from a disease by treating them with a vaccine.

The most effective public health intervention to protect people against infectious diseases. Vaccines train the immune system to recognise a pathogen and to defend the body from it at the next encounter.

Percentage of the population who has received a vaccine.

Centers for Disease Control and Prevention. The US’s federal health protection agency.

European Medicines Agency. A European agency that facilitates development and access to medicines, and evaluates new medicines so that they can be approved for use in people.

Food and Drug Administration. A US agency that regulates the safety, effectiveness and quality of medicines. It has a wider role in public health such as food safety and regulating tobacco products.

Chief Scientific Adviser. Most senior government adviser providing government departments with scientific advice. Most government departments have one. There are also CSAs for each of the devolved administration. The list is available here.

Chief Medical Officer. A qualified medical practitioner who is the most senior government adviser on health matters.

Department for Health and Social Care. A ministerial government department with overall responsibility for health and care services. It sets strategy, funds and oversees the health and care system in England, with equivalent counterparts in the devolved nations.

Government Chief Scientific Adviser. Chief Scientific Adviser providing scientific advice to the Prime Minister and members of Cabinet and coordinating the Chief Scientific Adviser network.

Joint Committee on Vaccination and Immunisation. A scientific advisory committee that advises the UK health departments on immunisation.

Medicines and Healthcare products Regulatory Agency. An executive agency of the Department of Health and Social Care. It regulates medicines, medical devices and blood components used in transfusions in the UK. It decides whether to approve new medicines such as vaccines.

National Institute for Health and Care Excellence. An arm’s length body accountable to the Department of Health and Social Care but is independent of government. Its role is to improve patient outcomes by producing national guidance and advice, and quality standards that set out what high quality and cost-effective care should look like.

National Institute for Health Protection. A new organisation responsible for public health protection. It will replace Public Health England and bring in other functions including the Joint Biosecurity Centre and NHS Test and Trace. It is expected to be operational in Spring 2021.

Scientific Advisory Group for Emergencies. Provides scientific and technical advice to the UK Government during emergencies.

Independent Scientific Pandemic Influenza Group on Behaviours. A scientific committee that provides advice about behavioural science. In the context of COVID-19 the committee has provide advice about how people can be helped to adhere to interventions that have been recommended. It provides reports to SAGE.