Friday, 2 May 2003

Rome (Fides Service) – The virus continues to infect more people and there is already talk of a vaccine. But we are far from a possible date for production and distribution even in approximate terms. Fides Service spoke with Prof. Tarsitani epidemiologist at S. Andrea Hospital of La Sapienza University in Rome. Prof. Tarsitani says it is not easy to answer questions about the possible production or utility of an anti-SARS vaccine and that we must proceed gradually in order to form an idea on the basis of the information available. First of all it must be said that SARS is a syndrome, it is not a well defined disease, which means that some of the cases reported present pathologies which have in common symptoms that constitute the syndrome (pneumonia with high temperature and coughing). It is clear, says Tarsitani, that what we would like to do is to identify the episodes sustained by one or two common species of corona-virus which at the moment are thought to be the main pathogen agents, modified by causes not yet clear (via animals?). This premise serves to emphasise that the available epidemiological data is certainly distorted by a super- estimate of the disease against which we wish to vaccinate, because in the danger areas any sort of pneumonia is classified as SARS. If we evaluate the numerical consistence of the phenomenon we realise that we are faced with a morbid syndrome little diffused and which, except in certain parts of southern China, would appear to be under control. The conditional in this case is compulsory! It would also seem a scarcely contagious disease; to understand what I am saying – the doctor continues – try to imagine putting a child with chickenpox in a class of non vaccinated children, rest assured that within a short time they will all be infected. If you put a child with a common cold among other children, by respecting a few rules of hygiene the disease will only partially spread, and this seems to be the situation of SARS, sustained by a modified cold virus. Why is this reflection on SARS’ mode of transmission and contagion important? Because in terms of public health, we are confronted with a disease which has a high mortality rate (5-15%) but a reasonable rate of diffusion which can be controlled by normal procedure of direct prevention (inform, isolate, disinfect etc.) these are the practices to be preferred for its control; in any case this is the only path towards the formulation of a new vaccine which for use on humans requires much time, difficult to quantify: years, a decade, what is more, for some infective diseases no effective vaccine has ever been found. Moreover if SARS, as it is to be hoped, remains limited to a small number of people (thousands or tens of thousands, but not millions) it will be very difficult to find anyone willing to risk the enormous financial investments required for the production of a new vaccine, in the face of uncertain application. Therefore as things stand we should focus all our attention on norms of direct prevention and health surveillance. If in this way we succeed in keeping control of the epidemic this will be an important success. If the epidemic genius of the new virus manages to overcome the barriers we erect to stop its diffusion, then certainly the search for a new vaccine, which has in any case already begun, will receive more impulse. It will not be easy, because this type of virus is not usually studied, (the common cold is of little importance) and tend to change antigen structure and this may render necessary the continual preparation of new formulations, similar to the anti influenza vaccine; but we must not limit research. Another sector which will obviously develop concerns the production of antiviral drugs; this too is no easy challenge. If we look at the past twenty years, research for defence drugs able to counter AIDS has produced certain anti-retroviral drugs which have improved diagnosis of the disease and, so far, only prospects for some type of vaccines not at the stage of being used.
To conclude, let then us keep strictly to our old norms of hygiene, the only ones practicable at the moment, and, with regard to treatment and vaccines, we must realise that this will require lengthy experimentation, while nourishing the hope that it will not be necessary. AP (Fides Service 2/5/2003 EM lines 55 Words: 751)