One dose of swine flu vaccine is enough to prevent H1N1 infection

Studies from vaccine makers  CSL and Novartis suggest single dose of H1N1 is sufficient to provide immunity

Single dose of swine flu vaccine is enough to prevent a possible pandemic H1N1 influenza A infection.

Swine flu vaccines are currently prescribed and administered in two dozes to ascertain the expected immunity level against the lethal H1N1 virus.

Even WHO was recommending two dozes of swine flu vaccine to give sufficient protection against pandemic H1N1 strain. Because it is a new strain, infectious disease experts had said people would likely need two doses to get full immunity against the virus.

Two studies, however, published a leading medical journal confirmed that a single dose of swine flu vaccine can protect people from the new pandemic H1N1 virus.

One of the studies comes from Australian vaccine maker CSL Inc. CSL released new data suggesting its vaccine could evoke necessary immune response with a singe dose.

Australia’s leading biopharmaceutical company CSL Limited announced that preliminary data from the first study of its candidate pandemic H1N1 vaccine demonstrated a robust immune response in healthy adults after a single unadjuvanted 15mcg dose.

The data, published in the New England Journal of Medicine, showed that over 95% of participants receiving the single 15mcg dose of the vaccine achieved antibody levels that correlate with the prevention of influenza infection.

240 healthy adults aged 18 to 64 participated in CSL’s single-centre observer-blind study, randomised into two dose groups.

Preliminary data after the first vaccination demonstrated that post-vaccination antibody titres of 1:40 or greater were achieved in 96.7% of participants receiving the 15mcg dose and in 93.3% of participants receiving the 30mcg dose.

CSL data also showed that the vaccine has a tolerability profile consistent with seasonal influenza vaccines.

Swiss drug maker Novartis is the other company came out with studies supporting the efficacy of single dose vaccines.

Novartis said studies confirmed that its vaccine worked at an even lower dose when boosted with an immune system compound called an adjuvant.

Novartis vaccine, to be called Celtura, was tested with 100 healthy volunteers, aged between 18 and 50. The trial evaluated the tolerability and immunogenicity of the vaccine.

Novartis’ data showed that the serum antibody responses were highest among subjects who received two doses of vaccine, however a single vaccine dose also induced responses associated with protection against influenza.

Hemagglutination-inhibition titres reached 1:40 or greater in 80 percent and more than 90 percent of those receiving one dose and two doses respectively. These would satisfy the immunogenicity criteria as set out by European and US regulators.

The findings showed that it is possible to induce protective antibodies against A(H1N1) infection within two weeks of administration of a single low-dose adjuvanted vaccine, Novartis said in a press release.

“The study suggests that while two doses seem to provide better protection, one dose of our adjuvanted Celtura vaccine may be sufficient to protect adults against the swine flu. This is important information for public health authorities who prepare for vaccination in the coming months with limited vaccine supply,” stated Dr Andrin Oswald, CEO of Novartis Vaccines and Diagnostics.

Novartis is now conducting additional pivotal clinical trials, with larger numbers of subjects around the world. They will include more than 6000 adults and children, the release said.

China’s Sinovac also reported its vaccine protected patients with a single dose, last week. Sinovac Biotech Ltd., the first company to win Chinese government approval for a swine flu shot, said Aug. 18 its vaccine was safe and effective after a single shot.

Sanofi-Aventis, GlaxoSmithKline and AstraZeneca’s MedImmune unit and India’s Serum Institute are among those nearly 20 companies  racing to develop H1N1 vaccine.

H1N1 swine flu, which is declared a pandemic in June, could eventually infect one third of the world’s population, or 2 billion people, according to the World Health Organisation.

Swine flu has become the world’s fastest-moving influenza pandemic, spreading across 177 countries in the four months since it was first identified, according to the U.S. Centers for Disease Control and Prevention based in Atlanta.