This article provides a short note on Modern Research in Malaria Vaccines.
Worldwide efforts in basic research in malaria vaccines are at last beginning to bear fruit. In the United Republic of Tanzania in 1994 a double-blind phase III trial of the Colombian SPf66 peptide vaccine demonstrated that it reduced the numbers of first malarial fevers in children by around a third.
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Continuing studies with this and other vaccines are yielding additional data that will form the basis for recommendations for their use.
In the meantime, emphasis is being placed on strengthening national capacity to diagnose and treat malaria; epidemic preparedness and control; and mobilising sustainable international commitment for long-term malaria control.
In the countries of Africa, south of the Sahara, special attention is being given to strengthening general health services and enabling health care providers from other sectors and the communities themselves to provide early diagnosis and prompt treatment, i.e., disease management.
In the rest of the world, the emphasis is on improving the provision of basic curative services at all levels of health care and the promotion of rational drug use; and implementing selective measures for disease prevention, including selective vector control.
A dengue vaccine is already developed in Thailand with WHO’s help. The results of clinical trials in adult volunteers show that it is safe and its immunological response is encouraging. Trials of the vaccine in children have also begun.
A live, attenuated, highly efficacious vaccine for yellow fever is available and widely used, including in the Expanded Programme on Immunization in many countries. Protective antibodies appear 7-10 days after immunization and probably persist for life, although re-immunization is currently recommended every 10 years. Other interventions centre around prevention of bites from infected mosquitos.
Urban transmission of yellow fever is essentially identical to that of dengue fever, a rapidly increasing public health problem in many countries of the tropics. Control of breeding of Ae. aegypti mosquitoes around houses should lessen the risk of urban yellow fever transmission as well as that of dengue fever.
Vaccines are available for Japanese encephalitis. They require an initial series of two injections, followed by a booster. Immunization is the most effective means of disease prevention. Efforts are under way to develop a live, attenuated vaccine that will be an improvement on the existing inactivated vaccine.
In filariasis, four major breakthroughs have occurred, offering the prospect that—given sufficient political commitment and resources—the disease might eventually be well-controlled or even eliminated.
The first of these breakthroughs is the development of safe, single-dose, annual drug treatments. Trials have proved that a single dose of diethylcarbamazine (DEC) is very effective even two years after treatment. A single dose of invermectin has proved to be equally effective. A combination of single doses of both drugs reduced microfilaria more than 95 per cent two years after treatment.
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Secondly, intensive local hygiene on an affected limb, with or without the use of antibiotic and antifungal creams, has been shown to have dramatic effects by halting the progression of—or even reversing—elephantiasis and lymphedema.
Thirdly, DEC-medicated table or cooking salt has been introduced in India. The carefully controlled addition of very low concentrations of DEC has long been recognised as an effective means of eliminating lymphatic filariasis infections in communities. However, the addition increases the price of the salt. The first commercially prepared DEC salt went on sale in India, at about twice the price of ordinary salt.
Finally, there has been the development of insecticide sprays and polystyrene beads to seal latrines and roof-top water-storage tanks, to eliminate or reduce populations of urban Culex mosquitos.
In general, the control of bubonic plague involves breaking the rodent-flea-human transmission chain by the use of insecticides, flea and rodent control and sanitation. Control of pneumonic plague aims at interrupting the respiratory route of person-to-person transmission. Antibiotics are effective in treating the disease.
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Flea control involves the use of insecticides blown into rat burrows or distributed around houses frequented by rats. Insecticides should be used before any rats are killed or a rodent control campaign is carried out, because otherwise fleas leave dead rats in search of another living host such as humans.
Plague vaccines exist but are not recommended for immediate protection in outbreaks. Vaccination is only recommended for high-risk groups such as health workers and laboratory personnel who are more intensely exposed to risk of contamination.
Because it is transmitted in the wild, plague cannot be eradicated in the foreseeable future. Surveillance at local, national and international levels is crucial in the prevention and control of the disease.