CSL says swine flu vaccine protects with one dose

WASHINGTON (Reuters) - Australian vaccine maker CSL Limited said on Thursday a single dose of its H1N1 swine flu vaccine would protect adults against the virus, a finding that means vaccine supplies can be stretched further than officials had estimated.

One 15 microgram dose of the CSL vaccine, which does not use an immune booster known as an adjuvant, got the desired immune response in 95 percent of the 240 adults tested, the company reported in the New England Journal of Medicine.

The results support reports last week from rival vaccine maker Novartis and China’s Sinovac, who separately reported their vaccines got protective immune responses in patients with one dose.

The new H1N1 strain of flu, declared a pandemic on June 11, could eventually infect a third of the world’s population, or 2 billion people, according to the World Health Organization.

Because it is a new strain, infectious disease experts have said people would likely need two doses to get full immunity against the virus. They are rushing to put in place vaccine programs as the weather cools in the Northern Hemisphere and the traditional flu season starts.

Other pharmaceutical companies like Sanofi-Aventis, GlaxoSmithKline and AstraZeneca’s MedImmune unit are also racing to develop H1N1 vaccine as governments scramble to secure supplies.

H1N1 vaccines will be given separately from regular seasonal flu shots, something global health officials admit could create a logistical nightmare. If patients will only need one H1N1 dose, that could ease the burden considerably.

For the CSL study, researchers gave two doses of vaccine to all 240 adults, aged 18 to 64.

“Each participant received an initial vaccination followed by a second vaccination three weeks later. The first group received 15 mcg of vaccine, the standard dose used for a single strain in the ... seasonal influenza vaccine, and the second group received 30 mcg of vaccine,” CSL said in a statement.

Blood tests showed 96.7 percent of the volunteers who got the 15 mcg dose had an immune repose that has been shown to protect people from flu.

“This immune response remains consistently strong irrespective of age. No deaths, serious adverse events or adverse events of special interest were reported,” CSL said.

The most common reported side effects were injection site tenderness and pain and headache, CSL said.

Separately, MedImmune officials said they had submitted safety data for their nasal spray swine flu vaccine to the U.S. Food and Drug Administration.

“There are no red flags there. We think we can have 5 million doses ready to distribute at the end of September,” MedImmune’s Dr. Raburn Mallory said in an interview. U.S. officials have not expected vaccination to begin until mid-October.

“Because our vaccine is a live vaccine it tends to have better one-dose efficacy than the killed vaccines,” he said.

Reporting by Maggie Fox, Editing by Julie Steenhuysen