Pneumococcal conjugate vaccines. A review

The pneumococcus is currently the most common cause of vaccine-preventable death in children aged less than 5 years, and in 2002 was responsible for 716,000 deaths worldwide. Treatment with antibiotics was the main approach to contain the pneumococcus, however, even with effective antibiotics, pneumococcal meningitis has a poor prognosis and with the emergence of drug resistant pneumococcal disease the need for prevention by vaccine was evident. The first born pneumococcal vaccines were polysaccharide vaccines that unfortunately did not protect young children. The most vulnerable age group of children, less than 2 years of age, were without any form of protection from the pneumococcus until the licensure of a conjugate vaccine. Conjugation of bacteria polysaccharides to carrier proteins has been a significant milestone in the work of vaccine development and has been previously used successfully in the production of the Haemophilus influenzae-print type b vaccine. The seven-valent pneumococcal conjugate vaccine was first licensed in the USA in 2000 and in the European Union this conjugate vaccine was licensed in February 2001. Currently, fourteen countries have included this vaccine in their immunization programmes. Vaccination policies are found to differ greatly across Europe due to differences in local epidemiological situation, and also due to economic considerations. However, many countries are reviewing their own policies based on available data on the burden of pneumococcal disease. This review aims to give an overview about the pneumococcus, the development of the pneumococcal conjugate vaccine, and its impact.