NYTimes: Scientists make progress on a vaccine for SARS
Lawrence K. Altman The New York Times
Tests on humans are set to begin next year
American and European scientists independently reported that they have protected animals from the SARS virus with two different types of experimental immunizations, raising hopes that they could ultimately be used among humans.
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One dose of an experimental vaccine sprayed into the nose fully protected a small number of monkeys against SARS, scientists at the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, said in a report to be published in The Lancet on Saturday.
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In the same issue, European scientists reported using a different strategy that involved injections of a human monoclonal antibody, a type of genetically engineered protein. The antibody prevented the development of lung damage caused by SARS, reduced the amount of virus growth in the lungs and prevented spread of the virus in secretions from the nose and mouth.
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Other scientists said the reports represented significant advances. But they and the authors of the reports said more research needed to be conducted before either technique could be turned into a marketed vaccine or prophylaxis. The American scientists expressed hope that they could begin testing their vaccine on humans next year if further studies showed it to be safe and effective.
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The American strategy is known as active immunization, the European as passive immunization, in part because it is not long lasting. But it presumably would last long enough to help stop an outbreak of SARS.
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Immunizations developed by either technique would most likely be given to health care workers with a dual aim - to protect them against SARS and prevent its spread to other people. Health workers were both victims and transmitters of the virus in the epidemic of severe acute respiratory syndrome last year.
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The American nasal vaccine was sprayed once each into four African green monkeys that, four weeks later, were deliberately exposed to the coronavirus that causes SARS. The monkeys showed no sign of the disease in their respiratory tracts, and blood tests showed that the animals had developed a type of protein known as neutralizing antibodies that best correlate with protection from disease.
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The scientists also sprayed four monkeys in a control group that did not receive the vaccine; the SARS virus replicated in all four.
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The vaccine was made by inserting the S, or spike, protein that protrudes from the SARS virus into a modified parainfluenza virus. The S protein helps the virus attach and enter human cells. Peter Collins, one of the American scientists, said that immunization with the protein alone stimulated a very strong immune response among the monkeys.
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In its current form, the American vaccine presumably would be most effective in young children because most adults have suffered respiratory infections caused by the parainfluenza virus. So the researchers are seeking to develop a different vaccine by using another virus into which the S protein could be inserted.
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The researchers say that the drug has "disappointingly little overall benefit" and is not cost-effective, and that better treatments are needed.
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Most studies have shown that the drugs can produce small improvements in patients' scores on mental tests, but it is not clear whether those gains translate into anything helpful in real life. Even the drugs' staunchest advocates say that they offer only modest benefits at best, affording perhaps a short delay in a patient's decline.
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The new report, published in Friday's edition of The Lancet, is based on a study of 565 patients with mild to moderate Alzheimer's disease who were assigned at random to receive either Aricept or a placebo and were then followed for up to three years.
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Although the patients taking the drug did have slightly higher scores on mental tests, after three years they did not differ from the placebo group in their rates of being put in a nursing home or becoming disabled. There were also no significant differences between the groups in behavioral or psychological symptoms or in the emotional well-being of the people taking care of the patients. Tests on humans are set to begin next year