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Bird Flu Vaccine Supply Shrinks with News It Takes
Double Dose to Work
Even then it only
worked in half the participants - no seniors included
 March 30, 2006 The U.S. supply of vaccine to
prevent bird flu (H5N1) just got cut at least in half by the report of a
clinical trial that found it took two doses to achieve immunity, and
that was only in about half the patients. This trial, incidentally,
included no senior citizens people over age 64 who are considered
most in danger should an avian flu pandemic strike.
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Related Stories |
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U.S. Now Has 26 Million Avian Flu Antiviral
Treatments to Fight Pandemic
Death toll at 27 in first three months of 2006,
compared to 44 in all of 2005
March 23, 2006 - HHS Secretary Mike Leavitt
yesterday
announced additional purchases of six million antiviral drug treatments
that could be used in the event of a potential influenza pandemic. With
these purchases, the Strategic National Stockpile will have a total of
26 million treatment courses of antiviral drugs for distribution to the
states when an influenza pandemic is deemed to be imminent. Deaths
worldwide from the feared Avian Flu or Bird Flu have now reached 27
compared to 44 for all of last year, according to the World Health
Organization. Read more...
Read more
on
FLU 2005-06 |
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Results demonstrate that high doses of an
experimental H5N1 avian influenza vaccine can induce immune responses in
healthy adults. That's the good news.
Only about half of those volunteers who received an
initial and a booster dose of the highest dosage of the vaccine tested
in the trial developed levels of infection-fighting antibodies that
current tests predict would neutralize the virus. That's the bad news.
The further bad news is that the dosage needed to
accomplish immunity in half the people was 12 times higher than that
needed for the annual seasonal flu shot.
Back to good news - the government and industry are
working on other types of vaccine.
The National Institute of Allergy and Infectious
Diseases (NIAID), part of the National Institutes of Health, funded the
study, published in the current issue of The New England Journal of
Medicine. Preliminary results from this trial were first disclosed late
last summer.
These findings represent an important step forward
in the nations efforts to prepare for the possible emergence of a human
pandemic of H5N1 avian influenza, notes NIH Director Elias A. Zerhouni,
M.D., in putting a positive face on the results.
We are working hard to address the many challenges
that remain with regard to the development of an H5N1 vaccine, adds
NIAID Director Anthony S. Fauci, M.D.
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Following are
highlights from an editorial in the New England Journal of
Medicine on this study. |
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Vaccines
against Avian Influenza A Race against Time
Gregory A. Poland, M.D.
Avian influenza A (H5N1) virus
poses an important pandemic threat. A study by the Congressional
Budget Office estimates that the consequences of a severe
pandemic could, in the United States, include 200 million people
infected, 90 million clinically ill, and 2 million dead.
The study estimates that 30
percent of all workers would become ill and 2.5 percent would
die, with 30 percent of workers missing a mean of three weeks of
work resulting in a decrease in the gross domestic product of
5 percent.
Furthermore, 18 million to 45
million people would require outpatient care, and economic costs
would total approximately $675 billion. As of March 10, 2006,
the World Health Organization (WHO) had reported 176 confirmed
human cases of influenza A (H5N1) across seven countries, with
97 deaths (a 55 percent mortality rate for identified cases).
● The virus is close to meeting
the criteria for a pandemic virus one that is new, can cause
human illness, and can be transmitted from human to human and
the world is currently in phase three of the six WHO phases of
alert for pandemic influenza (higher numbers represent greater
seriousness).
● Influenza A (H5N1) is not yet
pandemic because of a single factor: the inefficiency of
human-to-human transmission. Once such transmission is efficient
and sustained, even assuming that the current mortality rate of
approximately 50 percent decreases, we will be in the midst of a
serious pandemic.
● For this reason, maintaining
the public health requires attempts to mitigate, avert, and
treat infection with influenza A (H5N1) virus, and the key to
meeting these goals is the development, testing, licensing,
manufacturing, and stockpiling of vaccines.
●Safe and effective vaccines are
likely to be the single most important public health tool for
decreasing the morbidity, mortality, and economic effects of
pandemic influenza particularly in view of the reported
resistance of influenza A (H5N1) to antiviral agents.
● Thus, the data reported in
this issue of the Journal by Treanor et al. from their
multicenter randomized, double-blind, placebo-controlled
clinical trial of a subvirion influenza A (H5N1) vaccine are
important and informative.
● Additional factors for which
data are needed include differences in vaccine-induced immunity
according to age, sex, immune status, and ethnic group. Some of
these data could be derived from the results of Treanor et al.
on further analysis.
Age may be particularly
important; those who have died in past pandemics and from
influenza A (H5N1) infection are disproportionately children,
adolescents, and young adults.
● The National Institutes of
Health have funded studies of more than 30 candidate vaccines.
Early results from some of these trials should be available in
the next 6 to 12 months.
● Thirty years ago, the United
States attempted to respond to the threat of pandemic influenza
with a vaccine approach. Now, armed with a greater understanding
of the science, we have the capacity and the responsibility to
embark on multiple, parallel avenues of vaccine development.
In addition, we need efficient,
rapid, high-yield, low-cost manufacturing innovations; the rapid
generation of candidate vaccines for other, potentially pandemic
influenza viruses (including emerging clade-2 influenza A [H5N1]
viruses); and the rapid movement of those vaccines into clinical
trials.
In turn, this effort will
require creativity along the entire pipeline: in the development
and manufacture of candidate vaccines; the synchronization among
countries of regulatory approaches; the resolution of issues
concerning liability and intellectual property; ensuring the
efficiency of clinical trials; and the use of methods to
stockpile and rapidly deploy these vaccines.
To do otherwise, with the
pandemic clock ticking, could prove to be too little, too late.
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For example, potentially protective immune
responses were seen most frequently at the highest dose of this vaccine.
We are investigating other options that may allow us to reduce the
dosage for example, adding an immune booster, or adjuvant, to the
vaccine so we can achieve a more practical immunization strategy, he
said.
In addition, the agency said, the U.S. Department
of Health and Human Services is pursuing other approaches to an H5N1
vaccine, including vaccines made in cell cultures rather than grown in
eggs.
The researchers in this study specifically
concluded: "A two-dose regimen of 90 mcg of subvirion influenza A (H5N1)
vaccine does not cause severe side effects and, in the majority of
recipients, generates neutralizing antibody responses typically
associated with protection against influenza. A conventional subvirion
H5 influenza vaccine may be effective in preventing influenza A (H5N1)
disease in humans.
This bird flu vaccine was based on a virus strain
that killed a Vietnamese man in 2004.
H5N1 avian influenza viruses are of enormous
concern to public health officials worldwide. The potential for a human
avian flu pandemic looms large, say experts, as daily reports indicate
an increasing spread of infection in bird populations in Southeast Asia,
Europe, the Middle East and Africa.
According to the World Health Organization, as of
March 24, 2006, 186 people had been infected with avian flu viruses, and
more than half of them had died.
Generally, flu viruses are easily transmitted from
person to person, but so far, the H5N1 avian influenza viruses have not
demonstrated this characteristic. In the worst-case scenario, if an
avian flu virus became easily transmissible from person to person, it
could trigger an influenza pandemic because humans have no pre-existing
immunity to these viruses.
The trial, conducted between March and July 2005,
was carried out at three NIAID-supported Vaccine and Treatment
Evaluation Units located at the University of Rochester Medical Center
in Rochester, NY; the University of Maryland School of Medicine Center
for Vaccine Development in Baltimore; and the Los Angeles Biomedical
Research Institute at HarborUniversity of California Los Angeles
Medical Center. John Treanor, M.D., of the University of Rochester, led
the group.
The study was conducted in two stages. In the first
stage, the research team enrolled 118 healthy adults ages 18 to 64 years
old. Although none of these participants were senior citizens, other
trials in progress do include people 65 and older, these researchers
say.
Each participant was assigned at random to one of
five groups. Volunteers in each group received an initial dose of
vaccine (7.5 micrograms [mcg], 15 mcg, 45 mcg or 90 mcg) or saline
placebo into the upper arm muscle; about one month later, they received
a booster shot of the same vaccine dosage or the placebo. The research
team collected blood samples before each vaccination and one month after
the second vaccination.
Before the study could be expanded, an independent
Data and Safety Monitoring Board assessed the vaccines safety by
reviewing data collected through day 7 after the second vaccination; no
safety concerns were found.
The investigators then began stage two of the
study, eventually enrolling an additional 333 healthy adult volunteers
into the trial according to the same protocol design as in stage one.
The NEJM article describes an analysis of data on
the safety and immune responses to the vaccine.
In general, the higher the dosage of vaccine, the
greater the antibody response produced. Of the 99 people evaluated in
the 90-mcg, high-dose group, 54 percent achieved a neutralizing antibody
response to the vaccine at serum dilutions of 1:40 or greater, whereas
only 22 percent of the 100 people evaluated who received the 15-mcg dose
developed a similar response to the vaccine.
Generally, all dosages of the vaccine appeared to
be well tolerated:
● Almost all reported side effects were mild
● The second dose of vaccine did not cause more
local or systemic symptoms than the first
● Systemic complaints of fever, malaise, muscle
aches, headaches and nausea occurred with the same frequency in all
dosage groups as in the placebo group
● Lab tests did not reveal any clinically
significant abnormalities
The Voice of American reported that because the
necessary dosage is so high, it would be difficult to produce in
quantity for a significant portion of the world's population using
conventional methods.
So, VOA reports, researchers are turning their
attention to ways to stretch the vaccine using adjuvants, substances
designed to boost the immune system's response. If a study of 1,200
people across the United States shows that adjuvants enhance this
vaccine, each person might be able to get one dose instead of two,
making it available for more people.
But Dr. Fauci points out that, unlike seasonal
influenza, most people have never had bird flu, so they don't have
leftover immunity from the previous year, needing only a single booster
to deal with a new variant strain. He says everyone might need the
higher number of doses of a bird flu vaccine, just as an infant does the
first time it gets a seasonal flu shot.
"It's hard to tell," he added. "It's going to
depend on the response or how lucky we get with the adjuvants. It might
require two, because it's truly a primary immunization as opposed to the
secondary immunizations that we do with seasonal flu. We're going to
assume we need two, but hopefully we can get away with one if the
adjuvants work well."
Work is also under way on a vaccine based on a
second bird flu strain that has already begun to kill people.
About this study:
The vaccine, made from an inactivated H5N1 virus
isolated in Southeast Asia in 2004, was manufactured by sanofi pasteur,
Swiftwater, PA, under contract to NIAID. Because there are no
manufacturers licensed in the United States to use adjuvants in
inactivated influenza vaccines, NIAIDs first step was to test an H5N1
influenza vaccine made in a way that mimics the process used to make
conventional flu vaccines. The clinical data collected in this study are
now available to support the potential use of this vaccine should it be
needed for an emerging pandemic.
NIAID is a component of the National Institutes of
Health. NIAID supports basic and applied research to prevent, diagnose
and treat infectious diseases such as HIV/AIDS and other sexually
transmitted infections, influenza, tuberculosis, malaria and illness
from potential agents of bioterrorism. NIAID also supports research on
transplantation and immune-related illnesses, including autoimmune
disorders, asthma and allergies.
The National Institutes of Health (NIH) The
Nation's Medical Research Agency includes 27 Institutes and Centers
and is a component of the U.S. Department of Health and Human Services.
It is the primary federal agency for conducting and supporting basic,
clinical and translational medical research, and it investigates the
causes, treatments, and cures for both common and rare diseases. For
more information about NIH and its programs, visit
http://www.nih.gov.
Click here to article in New England Journal of Medicine
Click to editorial by Dr. Gregory A. Poland
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