Feds Weigh Future of Bird Flu Vaccine
By ANDREW BRIDGES
WASHINGTON – A bird flu vaccine that’s even less effective than previously thought could still play an important role in protecting against the increased likelihood of a pandemic, a government health official said Tuesday.
A panel of federal health advisers was weighing whether to recommend government approval of the vaccine, made by Sanofi Aventis SA.
The Paris-based company believes the benefits of the vaccine outweigh its risks. The Food and Drug Administration said the vaccine is safe but it remains unclear whether it’s effective.
In a clinical trial, the two-shot series appears to provide protection to just 45 percent of adults who received the highest dose. An earlier, interim analysis of the same study had suggested it prompted a protective immune response in 54 percent of patients, when measured 28 days after getting the second of two shots.
Despite its limited effectiveness, the vaccine still could prove better than nothing in an outbreak, said Norman Baylor, director of the vaccine office at the FDA.
"The benefit of having a licensed vaccine against a potential pandemic influenza virus strain must be weighed against the risk of having no vaccine at the time of an inevitable influenza pandemic," Baylor told the panel of experts. Baylor also said even a single dose of the two-shot vaccine could help combat the deadly bird-flu strain called H5N1.
The FDA is asking its experts whether Sanofi provided enough data to back approval of its bird flu vaccine or if more are needed. The agency isn’t required to follow the advice of its advisory committees, but usually does. The vaccine is the first against the H5N1 influenza strain to seek FDA approval.
Effectiveness was measured by the antibodies patients developed against the flu strain. The results appear to fall well below what’s expected of seasonal flu vaccines. Those regular flu shots, for example, protect 75 percent to 90 percent of vaccinated adults younger than 65.
The newer analysis used final data, while the earlier study used interim results, Sanofi said. The later analysis also used tougher standards to show the vaccine works, according to company documents released by the FDA.
The modest protective effects of the vaccine were seen in patients who received two 90-microgram doses of vaccine. The two shots contain 12 times the 15-microgram dose contained in regular winter flu shots.
Already, there are further studies under way that are looking at the use of immune boosters, called adjuvants, to try to improve the effectiveness of the H5N1 vaccine. Eventually, adjuvants also might shrink the needed dose for a pandemic vaccine closer to what’s now used in seasonal shots.
Health officials also are studying the development of cell-based vaccines, which would be faster to produce in an outbreak of deadly flu than are current egg-based vaccines. The FDA suggested the Sanofi vaccine, if approved, could be used on an interim basis until others are developed.
Sanofi’s Kenneth Guito called the company’s H5N1 vaccine "an important first step" in preparing for an outbreak of bird flu in humans.
The government plans to buy and stockpile enough bird flu vaccine for 20 million people, including emergency and health care workers. The Sanofi vaccine wouldn’t be sold commercially.
Since it began ravaging Asian poultry farms in late 2003, the H5N1 strain of bird flu has killed at least 167 people worldwide, according to the World Health Organization. Health officials worldwide worry the strain could mutate into a form that easily spreads from person to person, sparking a pandemic.