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Glossary of Terms




The Accelerated Development and Introduction Plans (ADIPs) address the significant technical, epidemiological and financial challenges involved in making new vaccines available that are to be used primarily in developing countries. The ADIP approach includes establishing value through epidemiologic disease surveillance and technical support, communicating value to the public and national and international decision-makers and donors, and delivering value through financial and logistical mediation and support. The three projects endorsed by GAVI are: The Rotavirus ADIP, the Pneumococcal ADIP and the Hib Initiative.


Adjuvants are agents commonly added to a vaccine formulation which do not stimulate an immunologic response alone but can help to increase the immune response to other components of a vaccine or stimulate the immune system overall, thereby increasing the efficacy of a vaccine.

Advance Market Commitment (AMC)

An Advance Market Commitment (AMC) is an innovative financing mechanism with the potential to save millions of lives by accelerating access to vaccines that would not otherwise be available for many years. An AMC is a financial commitment to subsidise the future purchase of a vaccine not yet available if an appropriate vaccine is developed and if it is demanded by the poorest developing countries. An AMC is not a purchase guarantee, as industry will only receive the subsidised price if the product meets targeted standards, if countries demand the product, and if an affordable, long-term price can be negotiated with the individual vaccine manufacturers. For more information about AMCs:


The small, branched air-containing pockets of the lungs where oxygen inhaled during respiration passes through a thin membrane and into the blood stream. Carbon dioxide passes across these thin membranes and into the alveoli in the opposite direction to be exhaled. During pneumonia, molecules and other fluids released from the pneumonia-causing agent (either bacteria or viruses) and from cells of the immune system coat much of the alveoli’s membranes, slowing or blocking the absorption of oxygen into the bloodstream, which then results in increasingly difficult breathing.


An agent – either chemically synthesized or isolated from fungi or other organisms – that kills outright, or is detrimental to, the growth of bacteria.


A protein found in the blood that is produced by specialized cells of the immune system (B cells) in response to foreign substances (e.g. bacteria or viruses) invading the body. Antibodies protect the body from disease by binding to their specific target (antigen) and marking them for destruction by other cells of the immune system. Antibodies are one of the major components of a healthy immune system.


Any substance foreign to the body that evokes an immune response either alone or after forming a complex with a larger protein. Antigens are active components of a vaccine that stimulate the body to produce antibodies, which in turn fight off disease.

Antimicrobial resistance

Antimicrobial resistance can develop in any type of microbe (germ). Microbes can develop resistance to specific medicines. Antibiotic resistance occurs when a bacterium or other microbe has mutated in some way such that it can resist the effects of an antibiotic or other medicine. This resistance then allows the microbe to continue to survive and multiply. A common misconception is that a person’s body becomes resistant to specific drugs, but it is the microbes, not people, that become resistant to drugs.


Literally "against-virus" – any medicine capable of destroying or weakening a virus.

Attenuated vaccine

A vaccine in which a live virus is weakened through chemical or physical processes in order to produce, in a vaccinated person, an immune response (and resulting protection against disease) without causing the severe effects of the disease. Attenuated vaccines currently licensed in the United States include measles, mumps, rubella, polio, yellow fever and varicella. Also known as a live vaccine.

Auto-disable syringes (AD syringes)

Syringes that have a blocking mechanism to prevent their re-use. They are an important feature for preventing the transmission of HIV and other highly infectious, blood-borne diseases.


Bacteria / bacterium

Tiny, one-celled organisms present throughout the environment that require a microscope to be seen. While not all bacteria are harmful, some cause disease. The term “bacteria” is used to indicate the plural form and “bacterium” is singular. Examples of bacterial diseases include diphtheria, pertussis (whooping cough), and tetanus. Bacteria such as the pneumococcus and Haemophilus influenza cause serious conditions like pneumonia and meningitis.


Bacteremia occurs when the blood becomes infected with bacteria. The infection may spread through the blood to other organs, which can lead to pneumonia, meningitis, shock and death. Septicemia, a related term, is the clinical term for “blood poisoning” and is used to describe a serious infection of the blood caused by bacteria or other microorganisms (such as viruses or fungi) or their toxins. Infections classified as septicemia generally progress quickly and are frequently life-threatening if not treated immediately.

Bacterial vs viral meningitis

Although meningitis can be caused by either a virus or bacterium, the bacterial form is more severe and can also result in a life-threatening infection of the blood (septicemia).

Binax NOW® (antigen test)

A rapid, highly accurate test used to identify Streptococcus pneumoniae in urine or cerebrospinal fluid (CSF)

Binax study

PneumoADIP’s multi-site study aims to evaluate the utility of Binax Now® (an antigen test for Streptococcus pneumoniae) as an adjunct to culture of CSF for the diagnosis of pneumococcal meningitis in a variety of developing-country settings.

Birth cohort

A population of children born within a defined geographic area in a given period, generally one year. The birth cohort is used to estimate the number of surviving infants after accounting for the infant mortality rate. For example, to understand the proportion of children surviving until their fifth birthday in Malawi in 2007, we would compare living children aged five to the 2002 birth cohort (the group of children born in the year 2002 in Malawi).

Booster vaccination

Further doses of the vaccine, given after the original (or primary) course, to maintain, increase or regain levels of immunity by stimulating immunological memory. This boosts protection against disease in a rapid ("secondary") immune response.

Burden of disease

A measure of the impact of disease in a population as measured in mortality, morbidity or economic terms. Knowledge of the burden of disease can help determine where investment in health should be targeted. For example, 90% of the up to one million children under age 5 who die of pneumococcal disease each year are from developing countries who therefore bear the majority of the disease burden.



The condition of harbouring a pathogen within the body, usually without any symptoms of the disease, but with the ability to transmit the pathogen to other susceptible hosts. This condition may result from the inadequacy of the immune response to completely clear the pathogen from the body.

Case definition

The criteria by which the symptoms of a patient can be judged to represent a case of a particular disease

Cerebrospinal fluid (CSF)

The sterile fluid around the brain and spinal cord. The CSF contains immunologic and, in cases of infection, viral or bacterial proteins and other by-products which are useful for diagnosis of meningitis and identification of the causative agent.

Cohort study (see also “Birth cohort”)

An epidemiological study design in which a group of individuals are followed over time to look at their disease risk factors. Individuals who develop disease are then compared to healthy individuals with respect to risk factors.

Cold chain

The system used for keeping and distributing vaccines in good condition. This consists of a series of storage and transport links, all of which are designed to keep the vaccine at the correct temperature until it reaches the user.

Combination (or combined) vaccines

Vaccines administered simultaneously as one preparation to protect against multiple infectious diseases or to prevent morbidity caused by multiple serotypes of the same pathogen. Examples are combined hepatitis A and B vaccines, the MMR (measles/mumps/rubella immunization), and the influenza vaccine that combines antigens representing three strains of influenza.

Conjugate vaccine

A conjugate vaccine contains an antigen (the immunity producing molecule) bound to a carrier protein (which will allow the antigen access to areas of a cell where the carrier protein may go). These vaccines are formulated by chemically linking sugar chains derived from the pathogen (the antigen) to a protein backbone. Some examples include Pneumococcal vaccines and HiB vaccines.

Country Multi-Year Plan (cMYP)

In late 2005, WHO and UNICEF, together with GAVI Alliance partners, developed guidelines for developing a comprehensive Multi-Year Plan (cMYP) for immunization to support countries in improving their planning for immunization. The cMYP process condenses current efforts to streamline immunization planning process at national level into a single comprehensive and costed plan. For more information, please visit

Coverage rate

The percentage of people in a population who have been immunized with a given vaccine. Since the World Health Organization introduced its Expanded Program for Immunization (EPI) in the early 1970’s, worldwide coverage of childhood vaccination has increased dramatically. Worldwide, only 20% of children were vaccinated with DTP3 (Diptheria-tetanus-pertussis) in 1980 and this rate had nearly quadrupled to 78% by 2003. If we consider, however, the population of each country individually, the coverage rate for DTP3 in 2003 varies from less than 40% up to 99%.


Developing Country Vaccine Manufacturers Network (DCVMN)

The Developing Country Vaccine Manufacturers Network (DCVMN), founded in 2000, is a voluntary, public health-driven alliance of enterprises – state-owned and private, large and small – from developing and middle-income countries. Its members have a shared interested in global networking and collaboration. Many produce WHO prequalified vaccines for both domestic and international markets, including the GAVI Alliance, UNICEF, the PAHO Revolving Fund and WHO. Full members, located in countries with fully functioning national regulatory authorities, are pre-qualified by WHO to supply vaccines, including BCG, DT, DTwP, OPV, TT, M, MR, MMR, Hep-B. & YF. Most members are expanding capacity and adding new technologies, including DTwP-based combination vaccines and Hib vaccine, and many are investigating rotavirus, pneumococcal, influenza and other vaccine needs.


A bacterial infection of the upper respiratory tract that can cause sore throat, fever and infection of the nasal passages. Diptheria has been nearly eliminated in the developed world by widespread vaccination.

DTP3 (Three doses of Diphtheria, Tetanus and Pertussis)

Three doses of Diphtheria Toxoid, Tetanus Toxoid and Pertussis vaccine are needed for full protection. The coverage of DTP3 in a population is used by GAVI as a measure of immunization program strength. One of GAVI’s goals is for all countries to achieve routine immunization coverage (DTP3) at 90% nationally with at least 80% coverage in every district by 2010.

DTaP (Diphtheria, Tetanus and acellular Pertussis vaccine)

Diphtheria, Tetanus and acellular Pertussis vaccine (DTaP), was introduced in 1997 to meet the regulatory requirements of developed countries. DTaP is a newer, more expensive vaccine than the older DTwP, and contains only certain pieces of the whole bacterial cell.

DTwP (Diphtheria, Tetanus, whole-cell Pertussis Vaccine)

Diphtheria, Tetanus, whole-cell Pertussis Vaccine (DTwP), is still used in most developing countries (and by GAVI) as part of routine immunization. This vaccine is formulated with a whole, inactivated bacterial cell.


Efficacy rate

A measure used to describe how well a vaccine reduces disease in an immunized population compared to an unimmunized (control) population. For example, in a study of a nine-valent pneumococcal vaccine in The Gambia, a 77% efficacy rate was observed for the vaccine, meaning that there was a 77% reduction in cases of invasive pneumococcal disease caused by vaccine serotypes among vaccinated children compared to children who received a placebo.

Efficacy study

A study measuring specifically how well a vaccine protects against the occurrence of disease. Two vaccine efficacy studies in Africa with the 9-valent pneumococcal conjugate vaccine in The Gambia and South Africa demonstrate that multi-valent pneumococcal conjugate vaccines are safe and effective even for HIV-positive children and have the potential to make a major health impact especially in rural settings where access to treatment is limited.

Expanded Program on Immunization (EPI)

Launched by WHO in 1974 as a global infrastructure to enable health systems in countries to deliver a series of basic vaccines to infants, this program is the foundation for routine immunization services throughout the developing world. Many countries still refer to their national immunization systems as ‘EPI’.


Gambia PCV Trial

A vaccine efficacy study in The Gambia of the 9-valent pneumococcal conjugate vaccine (PCV) in which it was demonstrated that multi-valent pneumococcal conjugate vaccines are safe and effective (even for HIV-positive children, as demonstrated by a trial of the same vaccine in South Africa ), and that the vaccine has the potential to make a major health impact, especially in rural settings where access to treatment is limited. All-cause childhood mortality was reduced by 16 percent in children who received the vaccine. In addition:

  • Children receiving the pneumococcal vaccine had 15 percent fewer hospital admissions than those who did not.
  • The nine-valent pneumococcal conjugate vaccine was 77 percent effective in preventing invasive pneumococcal infections caused by the serotypes included in the vaccine.
  • Overall, there were 37 percent fewer cases of pneumonia in the children who received the vaccine compared with children who received placebo.

GAVI Alliance

The GAVI Alliance (formerly the Global Alliance for Vaccines and Immunisation) was launched in 2000 to improve access to immunisation for children in impoverished countries. Governments in industrialised and developing countries, UNICEF, WHO, the World Bank, the Bill & Melinda Gates Foundation, nongovernmental organisations, vaccine manufacturers from industrialised and developing countries, and public health and research institutions work together as partners in the Alliance.

Key to achieving the goals of the Alliance is a dramatic increase in new funding for immunisation. Building on the resources already provided by individual partners in the Alliance, GAVI partners created The GAVI Fund (formerly the Vaccine Fund) to help fill critical gaps in the overall global effort and to maintain a significant source of new and additional financial support from public and private donors. GAVI resources help strengthen health and immunisation systems, accelerate access to selected vaccines and new vaccine technologies—especially vaccines that are new or underused, and improve injection safety.

GAVI-eligible country

Countries with less than US$1000 per capita Gross National Income (GNI) can receive GAVI support. There are currently 72 GAVI-eligible countries throughout the world that are designated as eligible for GAVI support based on World Bank economic classification.


Haemophilus influenzae type b (Hib)

A bacterium that can cause a range of illnesses including meningitis, bacteremia, ear, sinus and joint infections and pneumonia.

Haemophilus influenzae type b (Hib) Vaccine

One of the three under-used vaccines being made available to the poorest countries by GAVI/The Vaccine Fund (HepB, Hib and Yellow Fever): Safe and effective Hib conjugate vaccines were first licensed in the early 1990s.

Herd immunity

Herd immunity occurs when a large enough portion of a population (usually 90%) is vaccinated against a microbe (such as S. pneumoniae) such that transmission of disease to others is reduced. Unvaccinated people coming in contact with those who have received the vaccine therefore have a lower chance of becoming infected by that microbe. Within three years of commencing vaccination of young children with the 7-valent pneumococcal vaccine in the United States, infections caused by the strains contained in the vaccine decreased by more than 50% in adults aged 20-39 and nearly 30% in adults over age 60 . Despite having not been immunized with the 7-valent vaccine, adults are likely protected from the vaccine-specific strains by reduced exposure to young children carrying the bacteria.

Hepatitis B Vaccine (Hep B or HB)

One of the three under-used vaccines being made available to the poorest countries by GAVI/The Vaccine Fund (HebB, Hib and Yellow Fever): Hepatitis B is one of the leading causes of liver cancer and cirrhosis. A safe and effective vaccine against hepatitis B was first licensed in 1982, but had not been widely used in developing countries until GAVI was formed.

Hib Initiative

In 2005 the GAVI Alliance launched the US $37 million Hib Initiative, which comprises infectious disease experts from Johns Hopkins Bloomberg School of Public Health, the London School of Hygiene and Tropical Medicine, the U.S. Centers for Disease Control and Prevention (CDC), and the World Health Organization (WHO). The Initiative’s mission is to “expedite and sustain evidence-informed decisions at the global, regional and country levels regarding the use of Hib vaccination to prevent childhood meningitis and pneumonia.” An estimated 3.1 million cases of Hib disease occur each year in children under the age of 5 years, resulting in approximately 400,000 deaths.


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.

Immunity (Passive immunity)

Protection against disease by a human (or animal) antibody preparation (immunoglobulin). Protection is generally limited and wanes over time. Passive immunity is also conferred by maternal antibodies passing to the fetus before birth.

Inactivated vaccine

Inactivated vaccines consist of either killed organisms (i.e. Pertussis vaccine), inactivated microbial Exotoxin (i.e. Tetanus Toxoid), or purified fractions of micro-organisms (i.e. Pneumococcal vaccine). Inactivated vaccines are often weakly immunogenic and are thus less effective than live vaccines at inducing long lasting immunity. These vaccines are thus often combined with an adjuvant.or conjugated to boost effectiveness.


The number of new cases of a disease in a given period of time, among a specific population.

Invasive pneumococcal disease (IPD)

Invasive disease refers to the infection of a normally sterile site or fluid in the body, such as lung fluid, blood or cerebrospinal fluid. Non-sterile sites (and therefore, where non-invasive disease could occur) include the ear, mouth, skin, eye or respiratory tract. Forms of invasive pneumococcal disease include meningitis (cerebrospinal fluid), pneumonia (lung) and septicemia (blood).


Live attenuated virus vaccines

Live attenuated virus vaccines mimic natural exposure while being unable to cause disease, but do ideally induce immunologic memory and lifelong immunity. These vaccines generally require only one or two immunizations, since the immune responses they induce are very durable. Many licensed vaccines in use today are based on this concept. Examples include BCG (an attenuated for of mycobacterium to protect against TB) and oral polio vaccine.


Meninges / Meningitis

The protective membrane surrounding the brain and spinal cord. Swelling of the meninges during infection is called meningitis which can lead to paralysis, permanent neurological deficits and death. Both viruses and bacteria can cause meningitis and rates of bacterial meningitis – the more severe form – vary with seasonal changes in some areas of Africa, a phenomenon referred to as epidemic meningitis. Pneumococcus is one of the most important causes of both epidemic and non-epidemic meningitis around the world.

The Meningitis Vaccine Project (MVP)

The Meningitis Vaccine Project (MVP), a partnership created in 2001 by WHO and PATH, aims to eliminate epidemic meningitis as a public health problem in sub-Saharan Africa. The objectives of the partnership are to develop meningococcal conjugate vaccines for wide use in Africa, to monitor the effectiveness and safety of the vaccine and to assure its production at low cost.

Multivalent vaccine

A vaccine which can prevent infection from several different strains of a bacterium or virus. Examples of multivalent vaccines are:

  • Pentavalent vaccine
  • A vaccine which includes five antigens. GAVI provides the pentavalent Diphtheria, Tetanus, Pertussis, HepB and Hib vaccine to low-income countries. As of December 2004, 14 countries were receiving GAVI support for the pentavalent vaccine.
  • Tetravalent
  • A vaccine which includes four antigens. GAVI provides the tetravalent DTP-hepB and the tetravalent DTP-Hib vaccines. As of December 2004, one country received GAVI support for the DTP-Hib combination and 11 countries for the DTP-Heb combination.


A part of the nasal passage that lies above the soft palate and passes from the nose to the throat. The nasopharynx can be colonized by the pneumococcus for weeks to months and Pneumococcal carriage rates are inversely related to age, with up to 65 percent in preschool children, 36 percent in primary school children, and 25 percent in high school children in a study in the United States. As a consequence of their high and prolonged carriage rate and the method of transmission (respiratory droplets), young children play an important role in the transmission of pneumococcus, particularly in crowded settings, and households.

Non-vaccine type disease (non-VTD)

Disease due to infection with strain of the bacterium not contained in the vaccine formulation and thus against which the vaccine does not directly protect.



PATH, the Program for Appropriate Technology in Health is an international, nonprofit organization that creates sustainable, culturally relevant solutions, enabling communities worldwide to break longstanding cycles of poor

Pneumococal conjugate vaccine (PCV)

Pneumococcal conjugate vaccines are a class of vaccines that contain purified polysaccharides from the bacterial capsules of several strains of pneumococcus which are linked to a conjugate protein. The conjugation results in a boosting of the vaccine’s immunogenicity, a feature which is especially important in vaccines for children, whose immune systems are immature, and it is this feature which sets PCVs apart from the 23-valent polysaccharide vaccine for adults.

Two conjugate vaccines have been available since 2009, the 10-valent conjugate vaccine (PCV10), formulated to protect against 10 different strains of Streptococcus pneumoniae, and the 13-valent conjugate vaccine (PCV13), formulated to protect against 13 different strains of Streptococcus pneumoniae. The 7-valent conjugate vaccine (PCV7), a precursor to PCV13, is gradually being removed from the market as the "upgraded" version takes its place.

Different serotypes of pneumococcus have different regional distributions; the serotypes included in PCV7 accounted for between 49-80% of invasive pneumococcal disease (IPD) in children under 5 years old. The serotypes included in PCV10 and PCV13 provide higher coverage accounting for more invasive pneumococcal disease in all regions.

Pneumococcal disease (PD)

Pneumococcal disease can be any of a range of clinical syndromes including otitis media, pneumonia, bacteremia and meningitis caused by pneumococcal bacteria. Invasive pneumococcal disease refers to the relatively severe forms of the disease and is characterized by isolation of the bacterium from blood, spinal fluid, or another site in the body where bacteria are not usually found, i.e. normally sterile sites such as the blood and cerebrospinal fluid (CSF).

Pneumococcal polysaccharide vaccine (PPV)

An inactivated bacterial vaccine that prevents against infection with Streptococcus pneumoniae. The 23-valent polysaccharide vaccine (brand name, PneumoVax, manufactured by Merck) is routinely used in the elderly and other adults in the U.S. but is not as effective in infants as their immune systems are not as mature.

Pneumococcal protein vaccine

PATH’s pneumococcal vaccine effort builds on work begun in 2005 to produce protein-derived vaccines to prevent strains of pneumococcus not addressed by existing vaccines. The approach is aimed at identifying proteins that are common to most strains of pneumococcus. These “common proteins” could protect against the majority of types of pneumococcus in a single protein-based vaccine conferring broad immunity.

Pneumococcus / Pneumococci

The pneumococcus, whose latin name is Streptococcus pneumoniae, is a bacterium frequently found in the upper respiratory tract of healthy children and adults, is the leading infectious killer of children under the age of 5 worldwide and causes a range of infections – from relatively mild ear infections to potentially fatal pneumonia, meningitis and sepsis. The term “pneumococcus” refers to a single bacterium, while the term “pneumococci” is the plural form. Pneumococcus is not to be confused with streptococcus, a bacterium that causes sore throats and other infections.


A condition in which the alveoli (the tiny air-containing sacs of the lungs) become inflamed and fill with fluid, making breathing and adequate oxygen intake difficult. Although several agents such as viruses, funghi and other bacteria can cause pneumonia, Streptococcus pneumoniae is the leading cause of severe pneumonia in children in developing countries. According to UNICEF, Pneumonia kills nearly 2 million children under the age of five each year, much of which could be prevented by immunization with pneumococcal and Hib vaccines.1

Pneumo Medical Advisory Panel (PneumoMAP)

The Pneumo Medical Advisory Panel (PneumoMAP) is a group of expert clinicians and scientists that are committed to improving child survival globally, particularly in developing countries. Acting collectively, they work as an expert resource to educate UK, European and global parliamentarians and civil servants concerned with global health and overseas development aid.


The number of disease cases (new and existing) within a population at a given point in time.

Prevenar / Prevnar

Prevenar (also spelled Prevnar in some markets) is the brand name of a 7-valent pneumococcal conjugate vaccine used to prevent Streptococcus pneumoniae (pneumococcus) infections such as pneumonia, meningitis and septicaemia in infants and young children. Prevenar, manufactured by Wyeth, has been used in the US since 2000 and is also part of the routine immunizations in other developed countries. The vaccine includes antigens from the following 7 serotypes of pneumococcus: 4, 6B, 9V, 14, 18C, 19F and 23F.


Radiological pneumonia

Pneumonia diagnosed by a chest x-ray which shows increased density (which may be fluid) in the lungs

Randomized control trial (RCT)

The gold standard for the design of a clinical study where either treatment or placebo is randomly assigned to be given to each patient, ensuring as unbiased results as possible

Resistance profile

A listing of treatments or vaccines to which an infectious agent is resistant


Rotavirus is the most common cause of severe, dehydrating diarrhea among children worldwide. Each year it causes about 111 million cases of disease requiring home care only, 25 million clinic visits, 2 million hospitalizations and up to 600,000 deaths in children aged five or younger.


The Rotavirus Vaccine Program created by GAVI and the Vaccine Fund and based at PATH, is a target-driven approach to accelerating evaluation of and access to new rotavirus vaccines in developing countries.


Sensitivity Pattern

The sensitivity pattern for a given disease-causing organism refers to the set of antibiotics or other treatments effective against the infection.

Sentinel hospital

A hospital where close and constant monitoring and reporting of disease cases can be used to indicate potential outbreaks of disease. A group of sentinel hospitals spread across a region can be the basis for disease surveillance and contribute to our understanding of the distribution and magnitude of disease.


Also known as septicemia, sepsis is an infection of the blood that may be caused by a number of bacteria, including Streptococcus pneumoniae. Sepsis is often, but not always, associated with infection in another sterile body site, such as the lungs and is fatal in approximately 50% of cases.


A sub-classification of a virus or bacterium. The serotype is determined by the cell-surface proteins (antigens) of the virus or bacterium. Although there are more than 90 serotypes, not all of these are equally likely to cause serious, invasive pneumococcal disease. This, combined with the fact that current vaccine prevention strategies are directed against the capsule, together highlight the importance of understanding the distribution of capsular types in disease-causing organisms. The serotype distribution of these disease causing pneumococci vary to greater or lesser degrees according to age group, geographic region, nutritional status, HIV status and disease syndrome.

Serogroups are characterized by numbers, while the serotypes within a group are further characterized by adding a letter. Some serogroups have a single serotype within them and consequently have no letter to further define them. For example serogroup 1 contains a single serotype, therefore the notation is simply a “1”. However, serogroup 6 has 2 types within it named 6A and 6B. Sometimes there may be gaps in lettering of serotypes within a serogroup. For example, serogroup 9 contains types 9A, 9F, 9L, 9N and 9V.

Serotype replacement

Serotype replacement is part of a natural process whereby infections caused by certain strains of a disease (sometimes known as replacement disease) can occur with slightly elevated frequency once other strains have been suppressed by a vaccine or other intervention (e.g. antibiotics). Although there has been a small increase in disease caused by non-vaccine serotypes in populations using the already licensed pneumococcal conjugate vaccine, the US Centers for Disease Control and Prevention (CDC) estimates that in 2006, introduction of pneumococcal conjugate vaccine prevented approximately 30,000 cases of the severest forms (blood infections and meningitis) of pneumococcal disease among people of all ages. For more information, please visit

Sterile body site

Sites in the body that do not normally contain bacteria, such as the blood, lung fluid or cerebrospinal fluid (CSF) are said to be sterile. When these sites are infected, and the sterility is thus compromised, the condition is known as bacteremia or viremia. Normally non-sterile sites include the eyes, ears, mouth, nose and skin.

Streptococcus pneumoniae (SP)

See “Pneumococcus”


Consistent monitoring over time of the incidence or prevalence of a particular disease in a specified population. The PneumoADIP provides financial and technical support to surveillance sites for pneumococcal disease in 56 countries. By establishing the presence of severe disease, surveillance can demonstrate the potential for disease prevention and facilitates the setting of health priorities.



A vaccine is a preparation of killed or inactivated infectious agents or subunits of the agent’s components that is used to stimulate immunity. Once immunity is established, upon exposure to an infectious agent such as a virus or bacterium, the body can more quickly and efficiently recognize and neutralize the threat.

Vaccine pipeline

The term “vaccine pipeline” identifies vaccines currently in research and under development. In addition, the vaccine pipeline is divided into temporal, sequential phases of developing, testing and producing and licensing vaccines for public use. A 7-valent vaccine for pneumococcal disease in children is already licensed in more than a 75 countries worldwide and vaccines against 10 and 13 serotypes are in the late stages of clinical testing in the vaccine pipeline.


Valency indicates the number of distinct types or groups protected against in a given vaccine formulation. For example, the Prevnar vaccine contains protection against 7 types of pneumococcus and is thus said to be a “7-valent” vaccine. A vaccine protecting against 13 strains of S. pneumoniae, called the “13-valent” pneumococcal vaccine, is currently in the late stages of development.