Previous research had indicated two doses of vaccine would be needed, but results from the first swine-flu vaccine trials being run by Leicester University in the UK reveal a strong immune response after just one dose.
[Underlining the importance of this finding, concurrent research at the University of Maryland suggests H1N1 will be the dominant strain this year because it is clearly more contagious/communicable than the two main “ordinary” seasonal flu strains. This is partly because it is so new that hosts haven’t had a chance to build immunity & offer resistance. While ordinary strains infect 5% to 20% of a population, the World Health Organization warns H1N1 could infect “as much as a third of the world’s population.”]
The Leicester pilot study involved 100 healthy volunteers, aged between 18 and 50.
Dr. Iain Stephenson, who led the trial at the Leicester Royal Infirmary employing vaccine developed by Norvartis, a Switzerland-based company, said: "The clinical trial of Novartis MF59-adjuvanted cell-based A (H1N1) vaccine indicates that the ‘swine flu’ vaccine elicits a strong immune response and is well-tolerated. Results 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. [Adjuvanted vaccine “has material added to boost the immune response” - an approach the CDC says the US doesn’t anticipate using “at this time,” increasing the likelihood that two doses would be needed (though the US also has trials of adjuvanted vaccine underway).]
"The [Leicester] findings showed that it is possible to induce protective antibody against A(H1N1) infection within two weeks of administration of a single low-dose adjuvanted vaccine."
Non-adjuvanted formulations were not evaluated in this part of the study and will be evaluated shortly.
The trial evaluated the tolerability and immunogenicity of the vaccine, and tested different schedules of vaccination, in terms of time between vaccinations. The vaccine schedule was one or two doses of 7.5?g MF-59 adjuvanted surface-antigen A/California/2009 vaccine derived from cell-culture….
The research found the vaccine is well tolerated with pain at the injection site the most frequent adverse event….
Additional, larger pivotal trials with both cell culture and traditional egg based vaccines are already under way around the world that will include more than 6,000 adults and children. Timing on when the vaccine will be available to governments will depend on the results of these clinical trials, and approvals by regulatory authorities.
Source: University of Leicester news release Sep 3, 2009