There are two types of pneumococcal vaccine available in the UK:
Pneumococcal vaccine will be added to the routine childhood vaccination schedule from 4 September 2006. Evidence from other countries shows that where this has been done there have been dramatic direct benefits in terms of reductions in invasive pneumococcal disease, as well as acute otitis media, but that these are minor compared to indirect benefits from reduction of pneumococcal disease in the elderly, presumably due to a herd effect from reduced carriage in children (see e.g. MMWR 2005 / 54(36);893-897). In the Gambia, use of a 9-valent conjugate vaccine produced a benefit in overall child mortality beyond that explained by pneumococcal disease. This phenomenon needs to be explored further.
Types of pneumococcal vaccine
Pneumococcal polysaccharide vaccine
The vaccine that has been used for longest is a 23-valent polysaccharide vaccine. As the vaccine is a polysaccharide vaccine, however, it requires mature T cell function to produce immunity hence is ineffective below the age of 48 months.
Pneumococcal polysaccharide vaccine (Sanofi Paseur MSD) active provides protection against 23 serotypes of Streptococcus pneumoniae. These serotypes include pretty much all the serotypes likely to cause disease in the UK. It is licensed for prevention in those 2 years or older with increased risk for pneumococcal disease (eg 2 weeks before elective splenectomy or before immunosuppressive therapy).
Pneumococcal conjugate vaccines
Like other conjugate vaccines, these give long-lasting protection, even in infants. The polysaccharide is conjugated to a carrier protein eg tetanus toxoid, which enhances immune response. Prevnar as used formally in the UK contains 7 serotypes, which are responsible for about 85% of invasive disease in the UK and most of the world apart from Russia and Africa. These are also the serotypes most associated with penicillin resistance, although rare in the UK.
There is always the possibility that the serotypes covered by the conjugate vaccine will simply be replaced by others. This has been seen in a few studies eg nasal carriage in Alaskan children, however most areas have reported a sustained overall reduction in pneumococcal carriage and cases, even if non-vaccine serotypes make up a higher proportion than before.
Newer conjugate vaccines contain 9,11 or even 13 serotypes - these are appropriate for all those areas of the world where the 7 conjugate offers suboptimal cover, and may be able to hold off the spectre of serotype replacement for a little while.
- The Bristol Children's Vaccine Centre (BCVC), led by Adam Finn, which is undertaking "translational research related to mucosal vaccine development and specifically the mucosal immune response to the pneumococcus Streptococcus pneumoniae".