Combination vaccines in the South African setting.

The number of vaccines available and included as part of the national immunization schedules, has increased significantly over the past few decades. This impacts on patient/parent compliance and creates a challenge for health care providers for implementation of schedules necessitating training and infrastructure improvements. Use of combination rather than component vaccines offers advantages for compliance by single dose administration of various antigens, reducing stock costing as well as reducing cost of additional health care visits. Combination vaccines are often significantly more expensive than individual constituent vaccines. Concerns regarding an increased incidence of adverse events with use of combination vaccines have not been confirmed and rates may seem high as the adverse events seem to mimic the sum total of adverse event rates for each individual antigen used but may in fact be lower. Manufacturers typically advise against interchanging use of vaccine products. Despite this, health authorities advocate use of an alternative vaccine where the original vaccine in not available, to ensure continuity of vaccination. A notable exception is the acellular pertussis vaccine. Partly, because no serological correlates of immunity exist, but also a general lack of convincing follow up studies has prompted the recommendation for manufacturer fidelity for at least the first 3 vaccine doses. According to the South African Medicines Formulary, a variety of vaccines are available in South Africa. Although a large number are available in the private sector, the only true combination vaccine included in the current state EPI, modified in 2009, is the DTaP-IPV/Hib vaccine (Diphtheria, Tetanus, acellular Pertussis, inactivated Poliomyelitis virus and Haemophilus influenzae type b). There are many reasons justifying the use of combination vaccines rather that the individual constituent formulations. Implementation of use in the South African setting at this point is still limited, but may offer an exciting avenue of expanding the antigen repertoire without impacting on side-effects, efficacy or complexity of scheduling.