The bacteria Streptococcus pneumoniae causes potentially serious illnesses, including pneumonia, middle ear infections, meningitis and bacteremia (infection of the blood), and according to the World Health Organization (WHO) causes nearly 1 million deaths a year in children under 5. To combat this disease, there are currently two vaccines available. The vaccine most often used by adults is called the pneumococcal polysaccharide vaccine and the vaccine approved for use in children, even children under the age of 2, is the pneumococcal conjugate vaccine. Although the vaccines are similar, the components including the microorganism, the preservatives and the adjuvants are different.
Microorganism
Both the pneumococcal polysaccharide vaccine (PPV) and the pneumococcal conjugate vaccine (PCV) contain inactive virus. This means that the virus contained within the vaccine cannot cause an active infection.
PCV contains a mixture of seven pneumococcal bacteria serotypes. There are more than 90 known serotypes, but the seven represented in the vaccine account for 80 to 85 percent of the invasive pneumococcal disease in children, according to information published by Journal Watch.
The microorganism in PPV is a mixture of the 23 most prevalent serotypes of known pneumococcal bacteria. The components in the vaccine stimulate the body to produce antibodies against those specific types of bacteria.
Preservative
Preservatives are added to vaccines to prevent the growth of microorganisms, such as bacteria or fungus, in the event that the vaccine is contaminated. Because most vaccines are now distributed in single-use vials, the incidence of contamination is negligible, so preservatives are no longer a requirement.
PCV does not contain any type of preservative. PPV however does contain a 0.25 percent solution of phenol. Phenol is both a natural substance and a manufactured chemical that can be toxic in high doses. Phenol is often used in manufacturing disinfectants and antiseptics and in pharmaceuticals to prevent the growth of bacteria.
Adjuvant
An adjuvant is a substance added to the vaccine to increase the body's immune response. The addition of an adjuvant means that less vaccine is needed to induce the same protection. The PPV does not contain an adjuvant however the PCV contains an adjuvant that is a mixture of two substances. The PCV adjuvant contains Diptheria CRM197, a toxoid that is used to carry the pneumococcal components to the cells and aluminum phosphate the helps the components be absorbed by the cells. A study conducted in "Pediatrics Infectious Disease" concluded that the adjuvants used in the PCV are safe.
