In Canada, there are 100 to
200 cases of meningococcal disease each year. Without
treatment, the outcome is permanent brain damage or death
— even with treatment up to 15% of patients risk
dying. Fortunately, there are vaccines to prevent the
infection ever taking hold. A study in the July 24 issue
of The Lancet demonstrates how potent the vaccine's
protection can be. A British study, which analyzed four
years' worth of data from the meningococcal C vaccine
program concluded that the vaccine packs a longterm punch
provided that it's given in the first few weeks of life
and supplemented by a booster shot later on.
The UK program, which began in
2000, vaccinated infants at two, three and four months
of age. Older children and adolescents received a single,
'catch-up' vaccination.
Dr Mary Ramsay and colleagues from
the London-based Health Protection Agency looked at
the vaccination history of everyone in England who was
diagnosed with meningitis, caused by Neisseria meningitidis
serogroup C, from January 2000 through March 2004. This
allowed them to compare the effectiveness of the vaccination
when it had been given within the previous year as opposed
to more than one year ago.
"This showed us that vaccine effectiveness
remains high (approximately 90%) in children vaccinated
in the catch-up campaign (aged five months to 18 years),
but that in those infants vaccinated in the routine
immunization program (at less than five months of age)
effectiveness fell significantly after one year to low
levels," said Dr Ramsay. Indeed, the overall vaccine
effectiveness for the months-old infants fell to a paltry
66%.
Despite this dip, the results provide
"reassuring data," according to an accompanying editorial
in The Lancet. Dr Paul Offit from the University
of Pennsylvania and Dr Georges Peter of Brown Medical
School, write that "a booster dose for young infants
at 13 to 15 months of age would probably solve the challenge
of waning immunity in infants vaccinated at two, three
and four months of age."
Overall, the vaccination program
has been very successful. Since it was introduced in
2000, the number of cases of meningitis has plummeted
by 97% in those under age 20 (701 in 1998-99 to 16 in
2003-04). When all age groups are considered, there
was an 81% decrease in the same period, from 955 cases
to 63.
This is good news for Canadians
as well as Brits, as the same vaccine formula is used
in Canada as in the UK. The vaccine, a version called
Men C, consists of a portion of the sugar coat that
surrounds each meningitis-causing bacterium. This sugar
is attached to a protein so that when the vaccine is
injected, an immune response to both the protein and
the polysaccharide is induced.
Nonetheless, the effectiveness
of the Men C vaccine here in Canada remains to be quantified.
The Men C vaccine was only licensed for use in Canada
in 2001. If the UK study is any indication, the conjugate
vaccine could well prove to be effective in the longterm
for Canadian kids as well.
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