Current strategies for human rabies pre and post-exposure prophylaxis
Since their development more than 4 decades ago, concentrated and purified cell-culture and embryonated egg-based rabies vaccines (here jointly referred to as CCVs) have proven to be safe and effective in preventing rabies. These vaccines are intended for pre-exposure prophylaxis as well as post-exposure prophylaxis, and have been administered to millions of people worldwide. Rabies differs from many other infections in that the development of clinical disease can be prevented through timely immunization even after exposure to the infecting agent. In Asia and Africa, post-exposure rabies prophylaxis at its present level prevents approximately 272 000 deaths each year.
A power point presentation entitled WHO Guidelines for pre and post-exposure prophylaxis summarizing the WHO recommendations is attached for easy reference. For further information please consult the WHO position paper on rabies, Weekly Epidemiological Record, 2010, 85:309-320 and the Report of the WHO/Bill and Melinda Gates Foundation Consultation on Human and Dog Rabies Prevention and Control, Annecy, France, 7-9 October 2009, Ref: WHO/HTM/NTD/NZD/2010.1.
PrEP may be performed with any of the modern cell-derived vaccines and is recommended for anyone at increased risk of exposure to rabies virus. Traditionally, PrEP is recommended for anyone who is at continual, frequent or increased risk of exposure to the rabies virus either as a result of their residence or occupation (for example laboratory workers dealing with rabies virus and other lyssaviruses, veterinarians and animal handlers). Travelers with extensive outdoor exposure and children living in rural high -risk areas are at particular risk.
PrEP schedule requires intramuscular doses of 1 ml or 0.5 ml, depending on the vaccine type, or intradermal administration of 0.1 ml volume per site (one site each day) given on days 0, 7 and 28. To lead to significant savings, intradermal PrEP sessions should involve enough individuals to utilize all opened vials within 6–8 hours.
Booster doses of rabies vaccines are not required for individuals living in or travelling to high-risk areas who have received a complete primary series of pre-exposure or post-exposure prophylaxis with a CCV. Periodic booster injections are recommended as an extra precaution only for people whose occupation put them at continual or frequent risk of exposure. If available, antibody monitoring of personnel at risk is preferred to the administration of routine boosters. For people who are potentially at risk of laboratory exposure to high concentrations of live rabies virus, antibody testing should be done every 6 months. Those professionals who are not at continual risk of exposure through their activities, such as certain categories of veterinarians and animal health officers, should have serological monitoring every 2 years. Because vaccine-induced immunity persists in most cases for years, a booster would be recommended only if rabies virus neutralizing antibody titres fall to <0.5 IU/ml.
Children living in or visiting rabies-affected areas are at particular risk. WHO encourages the implementation of carefully designed studies on the feasibility, cost-effectiveness and long-term impact of incorporating CCVs into the immunization programmes of infants and children where canine rabies is a public health problem.