The enormous challenge of worldwide active immunization illustrates the need for products that confer passive immunity after exposure to viruses and certain bacteria. Homologous serum products, according to Wilde, are unaffordable or unavailable in most countries that need them. Heterologous sera from equine sources are less expensive to produce and are being manufactured in crude form in some countries in Africa and Asia. But a crude serum, with its high extraneous protein content, can induce serum sickness and anaphylaxis. To reduce these risks, Wilde is urging governments to encourage manufacturers to make partially purified heterologous sera, which can still be produced economically.
Governments are slow to respond.
Nevertheless, Wilde has succeeded in sparking interest on a few fronts. In preparation for starting its first rabies control project, Sri Lanka has sent a representative to study with Wilde in Thailand for 6 months. However, these figures are considered low because surveillance is poor in some countries. But calling for governments to encourage manufacturers to increase production of needed heterologous sera will not work, he asserted. Rupprecht favors more applied research and, in the case of rabies, greater focus on control of the disease in animals.