A new vaccine that protects against four strains of the bacteria responsible for invasive meningitis is safe and effective in young children, a team of British and Canadian scientists reported Tuesday.
If approved by regulatory agencies, the vaccine would be a potential advance over the current meningitis vaccines available for children under two, experts say.
But others noted the likely price tag of a quadravalent (four-strain) vaccine and the rarity of the additional strains that it covers may trigger long debate over what costs publicly funded vaccine programs can reasonably be expected to bear for a little extra protection — especially given that the durability of the protection won't be known for awhile.
"What's the marginal benefit of a vaccine which is four times more expensive or six times more expensive than the current one, without any knowledge of the long-term effectiveness?" said Dr. Philippe de Wals, a vaccine expert who heads Laval University's department of preventive and social medicine.
De Wals, who chairs Quebec's provincial immunization committee, was not involved with the study.
One of the Canadian authors acknowledged price and rarity of some of the strains may be used to argue against its use in publicly funded programs. But he suggested that approach might be shortsighted.
Dr. Scott Halperin said one of the strains covered by the new vaccine but not included in existing vaccines licensed for young children — the Y serogroup — may be on the rise. The Y strain causes only about 27 cases of disease in Canada a year, but is causing about 30 per cent of the estimated 1,400 to 2,800 cases that occur in the United States each year.
"The counter argument to that is that there is not Y disease right now," Halperin, a vaccine expert, said from Halifax, where he is director of Dalhousie University's Clinical Trials Research Centre.
"If Y disease is prevalent in the U.S., with time there's a good likelihood — not a certainty, but a good likelihood — it will be in Canada as well."
Vaccine designed to protect against four serogroups
The new vaccine, called MenACWY, is being developed by Novartis Vaccines and Diagnostics. The company sponsored the trial. The work was conducted by researchers from Oxford University's Oxford Vaccine Group and Novartis as well as Dalhousie University and British Columbia's Children's Hospital in Vancouver.
A total of 421 British and Canadian infants were either vaccinated with the new vaccine following a variety of dosing schedules or with an existing vaccine that targets one strain of the bacteria. The vaccine produced protective antibody responses in all the dosing regimes tested.
The results were reported Wednesday in the Journal of the American Medical Association. The vaccine is designed to protect against four serogroups — A, C, W-135 and Y — of Neisseria meningitidis, the bacterium that causes invasive meningococcal disease.
With its rapid onset and severity, the disease strikes fear in the hearts of patients. It kills an estimated 10 to 14 per cent of people who come down with it and about 20 per cent of people who survive suffer serious consequences such as neurological damage, limb amputation and hearing loss.
Fortunately, cases are rare. The Public Health Agency of Canada reports that there were fewer than 200 cases a year of invasive meningococcal disease in 2004 and 2005. Most cases in the country are caused by bacteria from the B and C serogroups — about 92 and 80 a year respectively, agency spokesperson Alain Desroches said in an e-mail.
There is no vaccine available against B strains in most parts of the world, but vaccines against C strains are in wide use in Canada.
The other serogroups in the new vaccine account for very few cases in this country, the public health agency's data show. In addition to the estimated 27 serogroup Y cases, the W-135 is estimated to trigger about 10 infections. Serogroup A causes fewer than one case a year in Canada.
Menactra strictly for adolescents
Based on that and other concerns, the National Advisory Committee on Immunization recommended against another new four-strain vaccine last year, Menactra.
The vaccine, made by sanofi pasteur, is licensed for adolescents in Canada. At least a couple of jurisdictions, New Brunswick and Prince Edward Island, have added it to their provincial immunization programs. But most have followed the advisory committee's recommendation, sticking with the C-strain vaccines they have been using for the past few years to vaccinate infants and teenagers.
The as-yet unlicensed Novartis vaccine has the same broad strain advantage as Menactra and, this research shows, another advantage as well. Where Menactra doesn't trigger a good immune response in infancy, one of the peak risk periods for meningococcal disease, the new vaccine does.
When the new vaccine hits the market, policy makers in Canada will have to re-evaluate public programs, de Wals said, though he noted a number of important questions remain to be answered.
"We don't know yet what is the relative effectiveness of different [delivery] schedules, what is the long-term immunogenicity of this new vaccine, what is the price of this new vaccine."