Published: September 10, 2009
Two investigational vaccines against the pandemic H1N1 flu appear to be safe and to yield a robust immune response with a single dose.
Those findings -- contained in two preliminary reports published online today in the New England Journal of Medicine -- are reassuring, experts said.
Among other things, vaccines that can produce an immune response with a single dose will stretch what is predicted to be a short supply of the drugs, according to Kathleen Neuzil, MD, of the University of Washington in Seattle.
Also, she wrote in an editorial accompanying the papers, immunity will appear more quickly -- soon after vaccination rather than after two doses at least three weeks apart.
The reports are "welcome and reassuring," Neuzil said, especially since a third online paper reported that few people currently have any immunity to the new H1N1 strain.The first of the preliminary reports published today is from a continuing study in Australia, where researchers are testing an inactivated H1N1 vaccine in a cohort of 240 volunteers, randomized to get either 15 or 30 micrograms of the drug.
Three weeks after vaccination more than 90% of volunteers had a robust immune response, according to Michael Greenberg, MD, of CSL, the vaccine's manufacturer.
Volunteers -- 175 adults, ages 18 to 50 -- were randomly assigned to receive:
- Two intramuscular injections of adjuvanted vaccine containing 7.5 micrograms of hemagglutinin on day zero in each arm
- Or one injection on day zero and the other on either day seven, 14, or 21
- Or two 3.75-microgram doses of adjuvanted vaccine 21 days apart
- Or 7.5 micrograms or 15 micrograms of non-adjuvanted vaccine, again given 21 days apart
The researchers are reporting data from 100 volunteers -- those who got the 7.5-microgram dose of the adjuvanted vaccine. (The manufacturer earlier gave some details of the findings. See Novartis Says Swine Flu Vaccine Works Quickly)
In that cohort, Stephenson and colleagues found, 86% of the volunteers reported adverse reactions after one or both doses -- primarily injection site pain and muscle aches. The reactions were generally mild or moderate and resolved after 72 hours, the researchers said.
For those who got two doses, the researchers said, more than 90% achieved "seroprotection" by day 21 -- defined as an antibody titer of 1:40 or more -- regardless of the dosing schedule.
"Generally, I think the results are good news," said John Treanor, MD, a vaccine expert at the University of Rochester in Rochester, N.Y.
He noted that the vaccine recently approved in China reportedly had good results with a single dose and other studies are still under way that should have data available soon.
"The overall impression I think, is that for adults, a single dose of vaccine will be sufficient," Treanor said.
One thing to consider, he said, is that the Australian study took place during the epidemic in that country, so that prevaccination antibody levels were higher than expected.
But the level of protection the researchers found is high enough that it seems likely the conclusion will stand up, he added.
The vaccines thus far have been given to healthy adults, so immunization of other groups may produce different antibody responses.
Richard E. Besser, MD, a former CDC deputy director who is now senior health and medical editor at ABC News, was also enthusiastic -- especially about the possibility that a single dose could produce immunity.
"This is very exciting news. It has many implications. It could double the number of adults who could be vaccinated. It will greatly simplify vaccination programs by no longer needing to track people between the first and second dose. It will greatly reduce the costs of vaccination programs," Besser said.
The results of the British study are also encouraging, Treanor said, although it's still too early to say what role the oil-in-water adjuvant is playing.
John Bartlett, MD, of Johns Hopkins Medical Institution, in Baltimore, agrees that the findings are encouraging. "The good news is that it suggests a single dose may be adequate," he said.
That's important for logistical reasons, as well as to stretch an available vaccine as far as it will go, said Robert Field, JD, PhD, of Drexel University in Philadelphia.
"It is dramatically easier to administer one shot than two," he said. "With a two-dose regimen, many people will neglect to get the second shot" -- sometimes for the simple reason that they don't know where to get the second shot.
"For instance," Field said, "if someone gets the first one at a supermarket, do they have to return there, can they get it at another supermarket, can they go to their physician's office, or can they go elsewhere?"
The Australian study was supported by CSL and the Department of Health and Aging of the Australian government. All authors report being employees of CSL and several report having an equity interest in the company.
The British study was supported by University Hospitals Leicester and Novartis. Stephenson reported financial links with Novartis Vaccines, Sanofi Pasteur, Baxter Vaccines, Hoffmann–La Roche, and GlaxoSmithKline.
The CDC study was supported by the CDC. Katz reported research support from GlaxoSmithKline.
The editorial author reported no conflicts.
Seeing who paid for the trials i wouldnt be putting too much faith in them - they have all been known to falsify reports in the past :/
No comments:
Post a Comment