Research News in the World of Travel Medicine
Malaria Vaccine progress
GSK has been developing a malaria vaccine for a long time based on circumsporozoite (CS) antigen. Sporazoites are the invasive stage of the malaria parasite injected in saliva by mosquitoes. Irradiated Sporazoites reliably produce immunity. CS antigen on its own does not produce immunity but works quite well when bolted onto the Hepatits B genetically engineered vaccine molecule. Trials are now into phase 3 and have just been reported. (1) Researchers report that efficacy is about 50% and slightly lower for the prevention of severe malaria. Three doses are given at one month intervals with a booster at 18 months. This would provide a significant reduction in the malaria burden in highly endemic parts of the world but will never be used in travellers at this level of efficacy. Anti-malaria prophylaxis (preventative tablets) achieves efficacy of at least 90% when taken properly.
Imported Rabies
An extensive review of 42 deaths over 20 years from 1990-2000 from imported rabies in Europe, USA and Japan has just appeared. 95% acquired their infection from a dog or puppy, 19 involving travel to Asia, 14 to Africa and 8 to the Americas. Of the 29 victims for whom information about post-exposure prophylaxis was recorded, 12 did not seek medical attention and 6 had ineffective care because of lack of supplies or knowledge.
Compared to road traffic accidents these are small numbers but all would have been prevented by pre-exposure vaccination and appropriate post-exposure care. Pre-travel vaccine removes the need for immunoglobulin treatment (which can be difficult or impossible to source, particularly in developing countries), reduces the number of post-exposure vaccine doses and reduces the risk of contracting rabies (2)
The RTS,S Clinical Trials Partnership, ‘First results of Phase 3 Trial of RTS,S/ASO1 malaria vaccine in African children’ New Eng J med 2011; 365: 1863-75
Malenczyk C, De Tora L, Gniel D ‘Imported rabies cases in Europe, the United States and Japan 1990-2000’ J Trav Med 2011; 18: 402-7
