Retention of a vaginal ring pessary in a postmenopausal patient.

The Hib vaccine has undergone several developments over the years. Initially an Hib polysaccharide (PRP) vacccine was developed. However, the immunological response to this vaccine was age dependent (as with other polysaccharide vaccines) with a poor response among those aged less than 2 years. Further development was undertaken; the Hib polysaccharide was conjugated to a carrier protein and this process then gave an effective vaccine that could be administered to the under 2-year age group. This has allowed many countries to include Hib vaccine in their national Expanded Program on Immunization (EPI). Despite this improvement, Hib vaccines are not affordable to many countries that need them most. In order to minimise the cost of production, a few studies3 have looked at the immunogenicity of reduced doses of Hib antigen in the vaccine. While these studies may differ with regard to which protein the Hib is conjugated to (tetanus toxoid protein (PRP-T) or mutant diphtheria toxin CRM197 (HbOC)), there is growing evidence that reduced amount of antigen in the vaccine, e.g 2.5 μg or 5 μg, is as protective as the conventional 10 μg dose.4 With such evidence coming through it is clear that the future of Hib vaccines will lie with the reduced Hib antigen.