SARS vaccine starts human trials
his month in China may have been contained, but it serves as a
timely reminder of the need for continued efforts to develop drugs
and vaccines for the virus, reports Phil Taylor.
Today, it was announced that Chinese scientists have started human trials of a vaccine against the coronavirus that causes SARS, thought to be the first time that a SARS vaccine has entered clinical testing.
The development is significant, because a lack of an animal model for SARS infection has made it difficult to establish the safety of candidate vaccines before starting trials in humans. To try to compensate for this, Sinovac has conducted preclinical tests in a broad range of animal species.
Four patients have received the vaccine so far, out of a total trial complement of 36. 24 subjects will get the vaccine, and 12 others will get the placebo. Each subject will get two shots. The first shot is on day 0 and is followed by a 28-day observation period, with the second injection given thereafter. The subjects will be observed until day 210, the Phase I trial end-date.
Sinovac Biotech, a biotechnology company based in Beijing, China, developed the inactivated vaccine with scientists at the Chinese Academy of Medical Sciences (CAMS).
Meanwhile, three other vaccines - all developed at Canadian universities - are due to start trials before the end of the year. And Aventis, Baxter International, Chiron and Protein Sciences are all working on vaccines that could enter the clinic in 2005 or beyond.
Aside from the lack of an animal model, another potential problem for the vaccine developers - albeit a welcome one from a public health standpoint - is that it will be very hard to test for efficacy in humans unless there is another major outbreak.
Another concern is that taking the vaccine may actually make SARS worse. This process, known as disease enhancement, has been encountered in trials of a vaccine designed to treat a similar coronavirus-based infection in cats.
SARS swept trough Asia and other areas of the world in early 2003. China was the country worst affected by the epidemic, with 5,327 people infected and 349 deaths attributed to the virus. In total, 774 people died around the world from the disease.