COLLEGE PARK – The first phase of a clinical trial on a vaccine designed to combat the avian flu virus is expected to conclude Oct. 31, as officials begin building a defense against a potentially deadly pandemic.
Experts at the University of Maryland Medical Center in Baltimore were asked to determine what would be optimal and safe dosages of a vaccine produced by pharmaceutical company sanofi pasteur to ensure a person was properly protected from the avian influenza virus H5N1, the deadly form that’s surfaced in Europe and Asia.
Sanofi pasteur provided researchers with 8,000 trial doses of the vaccine that was specifically designed to fight H5N1 avian flu virus, company spokesman John Abrams said.
James Campbell, the principal investigator for the study and assistant professor of pediatrics, said he and his collaborators at the University of Rochester and the University of California in Los Angeles determined that the vaccine should be administered in two doses.
“A single dose of the vaccine did not give people protective levels of antibodies in their blood,” he said.
Four different dose amounts were tested: 7.5, 15, 45 and 90 micrograms, Campbell said. The scientists found that the two largest amounts produced the most significant immune response.
The vaccine appears to be safe, Campbell said, adding that the 154 Maryland volunteers were monitored for red or sore arms or other adverse reactions to the intravenous shots.
“Still, whenever you test a new vaccine, you have to start with the assumption that there might be something that you weren’t expecting but could happen,” he said.
On Oct. 31, the scientists will draw new blood samples from the Maryland volunteers and take a last measure of antibodies in their blood. Those results will be compared to blood drawn before the first vaccine was administered and at two other stages during the study.
Antibodies are what the immune system makes to fight a foreign invader or disease, Campbell said. More antibodies detected in the blood means that the body is developing a better immune response to fight the avian flu.
Campbell said he didn’t know when, or whether, the vaccine would make it to the market.
“At this point, it’s hard to predict, but if the need arose, doses will be made,” he said.
According to Oct. 20 estimates from the World Health Organization, 61 people in Asia have died from the H5N1 strain since December 2003, and 118 cases of it have been confirmed.
The Centers for Disease Control and Prevention says the current risk to Americans is low if an outbreak occurs in Asia, but remains mostly confined. There was a brief scare in 2004 when another, less harmful, strain of the virus was discovered on two Delaware farms. Since 1997, millions of chickens and pigs worldwide have been killed to keep the virus at bay.
If the virus were to mutate and gain the ability to transmit from human to human, which it currently cannot do, containment becomes much more difficult, said Derek Cummings, a research associate at the Johns Hopkins Bloomberg School of Public Health.
Scientists worry that in Asia, where human contact with poultry isn’t well regulated, chances are high that someone will become infected with both a human and an avian flu strain, Cummings said. In that event, the two virus strains could easily exchange genes, and the avian strain would acquire the ability to transmit between humans. If that were to occur, CDC experts estimate that a “medium-level” pandemic could kill 89,000 to 207,000 people and render anywhere from 20 million to 47 million people sick.
So far in the government-directed sanofi pasteur trials, only 450 or so volunteers of a limited demographic have been evaluated at the three universities, Campbell said. Healthy men and women aged 18 to 64 were tested.
The next step in the trials would be to test children ages 2 to 9 and seniors over age 65. These further tests would only involve the two higher vaccine doses determined from Campbell’s current trial.
Maryland will continue to participate in these two trials; Campbell’s group is preparing for pediatric trials to begin in November.
Campbell also hopes to revise the first trial by giving the 154 Maryland volunteers a third booster shot, but that is pending the university’s approval.
With countries worldwide fearing the potential devastation an avian flu outbreak could cause, Abrams said that the U.S. government has put in a $100 million order for sanofi pasteur’s vaccine.
“This is $100 million worth of bulk, concentrated antigen that is kept in storage,” Abrams said of the September 2004 contract the company signed with the U.S. Department of Health and Human Services.
Consider this like buying concentrated powdered iced tea mix. The government has the tea mix, but it’s waiting on the clinical trials to designate the optimal ratio of mix to water that will produce the most effective product.
The Department of Health and Human Services has also tapped Chiron and MedImmune to create avian flu vaccines, Campbell said. Four other institutions join the University of Maryland Medical Center, the University of Rochester and the University of California in Los Angeles in a consortium that is evaluating and testing them.
The Chiron vaccine is scheduled to begin its clinical trials soon and MedImmune is just starting to develop its product, Campbell said. Eventually, all seven institutions likely will be testing the vaccines that the pharmaceutical companies produce. – 30 – CNS-10-21-05