THURSDAY, July 23 (HealthDay News) -- U.S. officials hope to have 160 million doses of injectable swine flu vaccine on hand by October, with more doses coming in the form of a nasal spray.
Since immunization is expected to depend on each person getting two doses spread a month apart, the amount of vaccine will still only cover a fraction of the population, but more is expected to arrive in the following months, the Associated Press reported Thursday.
Earlier in the day, the U.S. Food and Drug Administration convened a meeting with the world's five leading flu vaccine makers to assess how many doses might be available. Jerry Weir, an FDA official charged with overseeing vaccine production, told the AP that the H1N1 swine flu vaccine is proving more difficult to grow in the standard way (using chicken eggs) than typical seasonal flu vaccines. In fact, the yield is just 30 percent of normal.
The Department of Health and Human Services is responsible for buying up and distributing new vaccine stocks. Robin Robinson, who helps direct the HHS effort, told the AP that his team is keeping the production slowdown in mind as HHS buys and distributes new vaccine stocks.
But there was brighter news, as well. Maryland-based MedImmune Inc. told U.S. officials on Thursday that it expects to have 14 million doses of a swine flu version of its FluMist nasal spray vaccine ready to distribute across the United States by October, and would have even more available if it could fill its spray devices any faster. Tens of millions more doses will be ready to be bottled, the company said, and it's possible that a sprayer wont even be necessary -- it may be enough to administer droplets of the vaccine into the nose.
"A dropper instead of a sprayer works well," MedImmune vice-president Dr. Ben Machielse told the AP. MedImmune said it plans to begin trials in August to make sure the H1N1 version of the nasal vaccine has no more side effects than the vaccine for the seasonal flu.
Also on Thursday, experts at the U.S. Centers for Disease Control and Prevention said that the virus has not yet mutated to become more dangerous, although they continue to follow its progress globally, the AP reported. Dr. Nancy Cox, chief of CDC's influenza division, called the lack of genetic variation in the H1N1 strain "quite surprising" given the pathogen's quick spread.
In the meantime, the United States is readying its first human trials of an experimental vaccine to protect against the H1N1 swine flu virus, officials announced Wednesday.
Two potential vaccines will be tested at eight institutions around the country under the auspices of the National Institute of Allergy and Infectious Diseases (NIAID), officials said.
The purpose of the trials, said NIAID Director Dr. Anthony S. Fauci in a prepared statement, is to "determine whether the vaccines are safe and to assess their ability to induce protective immune responses. These data will be factored into the decision about how and if to implement a 2009 H1N1 flu immunization program this fall."
The announcement followed Tuesday's revelation that two Australian biotechnology companies have started inoculating adult volunteers in the world's first H1N1 swine flu vaccine trials. Experts hope those trials, as well as the trials planned in the United States, will produce an effective shot against the virus that has so far killed more than 700 people worldwide.
In the United States, several trials will be conducted concurrently, officials said.
"I think the speed with which they [federal officials] got this going is impressive," said one expert, Dr. John J. Treanor, professor of medicine and of microbiology and immunology at the University of Rochester Medical Center in New York. "They have a really well-organized clinical trials infrastructure that is uniquely posed to do these kinds of studies when there's an emergency situation like there is now."
One of the NIAID studies will try to determine if one or two 15-microgram doses of the candidate H1N1 vaccine are sufficient to provoke an immune response in healthy adults aged 18 to 64 and in people aged 65 and older. Studies will also look at whether one or two doses of 30 micrograms is more effective.
The two-dose regimens will be given three weeks apart. Two manufacturers, Sanofi Pasteur and CSL Biotherapies, produced the vaccines.
If these trials seem safe, the vaccines will also be tested in children aged 6 months to 17 years, according to the NIAID statement.
"The response to the vaccine may vary in different age groups," said Dr. Karen Kotloff, a professor of pediatrics and lead investigator at the Vaccine and Treatment Evaluation Unit at the University of Maryland, one of the medical centers chosen for the trials. In a statement released by the university, Kotloff explained that age could make a difference in vaccine response because "young people have not seen a flu virus like this before," whereas older Americans might have been exposed to H1N1-type strains in the past.
Additional trials will look at concurrent administration of the swine flu vaccine with regular, seasonal vaccine.
"It makes sense to test the combined swine flu and seasonal flu vaccines because there are some populations in whom both vaccines are indicated," Treanor said. "It would certainly be easier to give them at the same time, but these trials are mostly focused on making sure they don't interfere with each other in some way and that they still get a good response."
Besides the University of Maryland School of Medicine, other centers taking part in the trials include the University of Iowa; St. Louis University; Baylor College of Medicine in Houston; Children's Hospital Medical Center, Cincinnati; Emory University in Atlanta; Group Health Cooperative, Seattle; and Vanderbilt University in Nashville, officials said.
In Australia, Adelaide-based drug manufacturer Vaxine initiated trials Monday with 300 participants, while Melbourne's CSL has 240 people in its seven-month study. Australia had 14,703 confirmed cases of swine flu as of Wednesday, and at least 41 deaths, according to the AP. The winter flu season is well under way in the Southern Hemisphere.
Both companies said it would be at least six weeks before results of the initial trials are known.
Right now, flu season is peaking in the Southern Hemisphere. As was the case when the H1N1 swine flu virus first surfaced in Mexico and then the United States in mid-April, infections in the Southern Hemisphere continue to be relatively mild, much like the seasonal flu, and recovery is fairly quick.
As vaccine development continues, the H1N1 swine flu virus continues to sweep around the world.
The CDC reported last Friday -- the most recent day that numbers were available -- 40,617 confirmed cases of H1N1 infection and 263 deaths in the United States, although officials believe that more than 1 million Americans have been stricken with the swine flu. The reason for the disparity: The virus continues to produce mild symptoms and patients typically recover quickly.
Officials expect to see a new outbreak of H1N1 swine flu in the United States in the fall. It will most likely start earlier than seasonal flu, Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases, said during a Friday press conference. Seasonal flu typically surfaces in late fall.
Unlike seasonal flu, the H1N1 flu continues to pose more problems for younger people, Schuchat added. "There are higher attack rates and hospitalizations in younger adults and children," she said.
There's more on the flu at the U.S. Department of Health and Human Services.
SOURCES: John J. Treanor M.D., professor, medicine, microbiology and immunology, University of Rochester Medical Center, Rochester, N.Y.; July 22, 2009, news releases, U.S. National Institute of Allergy and Infectious Diseases, and University of Maryland School of Medicine; July 17, 2009, teleconference with Anne Schuchat, M.D., director, National Center for Immunization and Respiratory Diseases, U.S. Centers for Disease Control and Prevention; Associated Press