Background information on the Pneumococcal Conjugate Vaccine (PCV7)
Pneumococcal disease
Infections caused by Streptococcus pneumoniae in infants present an important cause of invasive disease such as meningitis and bacteremia, and non-invasive disease such as pneumonia and otitis media. Invasive Pneumococcal Disease (IPD) is associated with high mortality rates and may cause severe lifelong complications. Non-invasive pneumococcal disease causes a high burden to society due to the high incidence of infection-related disease, such as otitis media and pneumonia. In Western Europe, it is estimated that every child experiences one or more episodes of otitis media before the age of two years.
Conjugated pneumococcal vaccines
More than 90 serotypes of S pneumoniae exist, but the majority of diseases are caused by only a small number of serotypes. In addition, some serotypes are immunologically cross-reactive. In theory, providing immunologic protection against a small number of serotypes could protect against the majority of diseases caused by S pneumoniae. This assumption has been used in the formulation of the available vaccines. In the past, only vaccines using purified capsular polysaccharide antigens of S pneumoniae were available. Unfortunately, the antibody response to this type of pneumococcal vaccine in children aged <2 years is generally poor. Thus, these vaccines are not suitable for use in infants. To stimulate a sufficient immune response in young children, multivalent pneumococcal polysaccharide conjugate vaccines have been developed. In 2000, a 7-valent pneumococcal conjugate vaccine, known as Prevnar, was licensed for use in infants and young children in the USA. Other multivalent vaccine are under development: PCV9, a 9-valent vaccine is currently under development by Wyeth, containing serotypes 1 and 5 in addition to the serotypes 4, 6B, 9V, 14, 18C, 19F, 23F contained in the 7-valent vaccine; PCV10, a 10-valent vaccine is currently under development by GlaxoSmithKlyne and containing the serotypes of the 9-valent vaccine and 19A; PCV13, a 13-valent vaccine, is currently under development also by Wyeth, containing serotypes of the 10-valent vaccine and 3, 6A and 7F.