Conjugates

Current and Future Pneumococcal Conjugate Vaccines

There are 90 serotypes of the pneumococcus each of which has a different polysaccharide capsule. Even though there are a total of 90 serotypes, 88% of global disease is caused by 23 serotypes, and only 11 serotypes account for greater than 80% of disease in children under five. The number of different serotypes included in a vaccine is called its “valency.” In spite of the difficulties in building effective PCV vaccines, several are in the advanced stages of development while one, the PCV7 vaccine, is currently broadly administered in many developed countries.

The 7-valent PCV7 vaccine is in wide use around the world in developed countries. This vaccine contains seven of the most common disease causing serotypes (4, 6B, 9V, 14, 18C, 19F, 23F) in the U.S., Canada, Australia, and Europe and has been highly effective at reducing disease and eliminating the disparities associated with the disease in these countries.

Different serotypes of pneumococcus have different global distributions, however. While many of the seven included serotypes are common in the developing world as well, there are also other serotypes that need to be included in order to maximize the effect of the vaccine in the countries that need it the most, the countries of the developing world. Serotypes 1 and 5, for example, cause a much greater proportion of disease in developing countries than they do in developed countries. Serotypes 3, 7F, and 19A are also important serotypes to global disease burden.

Universal use of the PCV7 vaccine would prevent substantial morbidity and mortality in the developing world. A 10-valent, PCV10, and a 13-valent, PCV13, are currently under advanced stages of development. A 9-valent, PCV9, and an 11-valent, PCV11, are also being researched. These expanded valency vaccines would help prevent an even larger proportion of disease globally, with an especially needed boost of disease fighting power in the countries of the developing world. The 10-valent vaccine is expected to prevent 66-88 percent and the 13-valent vaccine 73-92 percent of pediatric pneumococcal disease depending on the region.

Proportion of pediatric pneumococcal disease prevented by PCV-7

Proportion of pediatric pneumococcal disease prevented by PCV-10

Proportion of pediatric pneumococcal disease prevented by PCV-13

PCV vaccines:

• are well tolerated in young infants.
• are well tolerated in people who are HIV positive.
• can be administered with other EPI vaccines and on the same schedule as DTP.
• pose no major safety concerns.
• can help to control the growing problem of antibiotic resistant strains of the disease.