Forattini, Oswaldo Paulo

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Cadernos Espinosanos (E-Journal)

E D I T O R I A LYELLOW FEVER AND VACCINATIONIt seems to be the opinion of the consensus that yellow fever represents a serious threat to the popula-tion for our country. That is what may be supposed from the far-reaching repercussions caused, as muchamong specialists as among the lay population, on the occasion of the publication, in the recent past, of thenews which reported the presence of the mosquito Aedes aegypti in various parts of the Brazil territory.The lay news referred to this mosquito in such a way as simply to confuse it with the infection itself.Even though there was no urban case, the origin of which could be imputed to the action of that vector,there can be no doubt that the possibility always exists. This is so because it is impossible to ignore the factof the existence of the yellow fever Flavivirus in Brazil, even though, until now, limited to the forestenvironment. In view of this the occurrence of human cases in urban zones infected by the Aedes aegypti,despite its forest origin, came to be considered a real risk, in view of the outbreaks possibility in the urbanenvironment. The public services, both federal and state, parallel to the combat against the urban vector,undertook a wide-reaching campaign of vaccination in those areas considered to be at risk, that is, thoseadjacent to the great forest regions of northern and central Brazil, susceptible to receiving and harboringthe cases which should arrive with the viral agent in the circulating blood.Among the reflections which such facts raise, it is that regarding the immunization of the exposedpopulation by means of the mass application of the available vaccine, known to be efficient. These thou-ghts, when they touch on a subject of as a polemic nature, arise again when one hints at the possibility ofincluding this vaccination as a routine practice. Leaving aside states of emergency which would justify thismass vaccination, one must weigh up various aspects. In a recent publication the World Health Organization(WHO, 1986), in dealing with the prevention and control of yellow fever in Africa, emphasizes certain basicprinciples which, mutatis mutandis, could provide information applicable to the Americas in general and toBrazil in particular.For the formulation of a strategy with a view to prevention, on the medium and long term, it is neces-sary to establish clearly defined objectives. These would include the delimitation of the endemic areas, theimplantation of a system of epidemiological surveillance, the prior establishment of plans for emergencysituations, the implementation of mass preventive immunization for the groups at risk and the control ofthe vector mosquitoes whenever possible. Clearly the putting to practical use of all the favorable conditionsand the identification of all the obstacles to be overcome is inherent in this strategy. It is still clearer thatthere is the need for the existence of an undertaking, in terms of health policy, at national level, in orderto guarantee the resources for these activities.Within this context one may relevantly include the attitude to be adopted in the policy of immunizationat the level of the population. Until recently, mass vaccination against yellow fever was prescribed, limi-tedly, as an emergency measure in epidemic situations. Such limitation is, however, being set aside and oneincreasingly observes changes in orientation in the sense that several countries have begun routine immu-nization programs on the basis of the expectation that one single vaccination could result in lasting protec-tion. Thus, ideally, a whole population might be protected, and this state of immunity would be maintainedby the routine vaccination of the infant and immigrant contingents. In this way, only a lack of resourcescould justify the limitation of immunization to the population at risk and to occasions of outbreaks ofthe virus disease, or in the face of the extreme likelihood of such events. There is therefore no doubt,judging from the arguments of the experts who undersigned the publication mentioned, tha t the ten-dency in vaccination against yellow fever is to include it in the routine of infant immunization, as from 9months of age, so as to coincide with the immunization against measles as already practised.In the light of these recent practices in Public Health, even though apparently limited to the Africancontinent, one cannot avoid wondering what the best course for a country like Brazil would be. On theoccasion of the wave of sensationalism which colored the lay news on the presence of Aedes aegypti, someexperts emitted opinions contrary to mass vaccination. However, apart from these episodes, it is time thereasons which could lead to routine anti-yellow fever vaccination in our national territory were pondered.The first one is, without doubt, the existence of the circulating viral agent. Although it is restricted to theprimitive forest environment, there is no way of denying the possibility of its migration to the modifiedareas where the presence of residual forests suggests the possibility of harboring those elements involved inthe zoonotic cycle, such as the occurrence of Haemagogus mosquitoes. The second is, incontestably, thepresence of Aedes aegypti in the urban environment, even that of large cities such as S.Paulo. Allow me todoubt the practical possibilities of its erradication in the way it was supposed to have occurred somedecades age. The present stage of urbanization, living habits, population density, the variety of recipients atpresent used, the means of transport, as well as other aspects, are totally different from those that were tobe observed at that time. Finally, there is no lack of mosquito species with vectorial possibilities which maybe in process of adaptation to the artificial environment. These culicidae, such as the Aedes scapularis forexample, might be capable of establishing a link between the forest and domiciliary environments, in as ormore efficacious a way that of the circulation of human cases with viremia.Thus here there is something which is deserving of the attention of our health authorities - i.e., thestudy of the possibility of the adoption of routine vaccination against yellow fever. At the very least as ameans to stimulate the search for a solution of the problem in a comprehensive way, not in a way that issimply centred on some aspects of its control at present known to us.REFERENCESWORLD HEALTH ORGANIZATION. Prevention and control of yellow fever in Africa. Geneva, 1986,Oswaldo Paulo ForattiniDepartment of Epidemiology of"Faculdade de Saúde Pública/ USP"

Yellow fever and vaccination

https://www.revistas.usp.br/rsp/article/download/23387/25419/

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