Pneumococcal Vaccine
Like other meningitis bacteria, the pneumococcus is covered by a capsule or coat made of a complex sugar called a polysaccharide. Although there are 84 different types of pneumococci, most cases of disease are caused by a much smaller number.
A polysaccharide vaccine is used in children, adolescents, and adults at increased risk of pneumococcal disease and is recommended for all those over 65 years of age. It contains purified polysaccharides against 23 strains of the pneumococcus which cause over 85% of all disease in older children and adults. Three brands of the polysaccharide vaccine are available:
- Pneumo 23®
- Pneumovax 23®
- Pnu-Immune 23®
Like almost all polysaccharide vaccines, the pneumococcal polysaccharide vaccine does not work in children under two years of age. A new vaccine for infants has been developed in which the purified polysaccharide is chemically linked to a protein (Prevnar®). The vaccine contains seven different polysaccharides from the seven strains which cause over 85% of severe pneumococcal infections in infants and young children in USA and Canada. The vaccine also reduced the frequency of cases of otitis media (ear infections) by 20%. The vaccine was licensed for use in the United States in February 2000 and in Canada in June 2001.
The new polysaccharide-protein conjugated pneumococcal vaccine (Brand name Prevnar®) is very safe. Rates of local reactions are slightly higher after pneumococcal vaccine than after diphtheria-tetanus-acellular pertussis vaccine (DTaP). Rates of fever and other generalized reactions are also slightly higher in infants given both vaccines at the same time than after DTaP by itself. When the pneumococcal conjugate vaccine is given at the same time as the combined diphtheria-tetanus-pertussis-polio-Hib vaccine, the immune responses are the same as when the vaccines are given at different times.
The new vaccine is very effective in preventing pneumococcal infections. In a study of over 37,000 infants in California immunized with the new pnuemococcal conjugate vaccine at 2, 4, 6, and 12-15 months of age, the vaccine was 97% effective in preventing bacteremia (infection of the blood stream) and meningitis. The rate of severe pneumonia was reduced by 33%. Since routine vaccination of infants became routine in the USA, the rate of serious pneumococcal infections in children less than 5 years of age has decreased 94%. Because the vaccine also reduces carriage of the vaccine strains, the spread of these strains has been reduced in all age groups. As a result, the rate of serious pneumococcal infections caused by the vaccine serotypes has decreased in all age groups, not just in vaccinated children. Among those over 65 years of age, the rate of severe pneumococcal infections caused by the vaccine strains has decreased by 65%.
The pneumococcal conjugate vaccine is recommended for routine immunization of all infants at 2, 4, and 6 months of age, followed by a booster at 18 months of age. Catch-up programs to immnize older infants and children less than 5 years of age will require 1 or 2 doses of vaccine, depending on the age of the child at the time of first vaccination. Since November 2005, the vaccine is available in all provinces and territories as part of the routine childhood immunization schedule at no cost to parents. It has proven to be as effective in Canada as it has been in the USA.
Recent studies have shown that 2 doses of the vaccine at 2 and 4 months of age plus a booster at 15-18 months of age is just as effective as the original 3+1 schedule. The revised schedule is now used in Quebec and British Columbia. Other provinces may also adopt it.
Routine use of the conjugate vaccine can be make meningitis and other severe pneumococcal infections become rare events in Canadian children.
