Avian Flu - Vaccine Mismatch - Tamiflu Resistance
- From: "Pat Gardiner" <patgardiner@xxxxxxxxxxxxxx>
- Date: Fri, 8 Feb 2008 23:21:24 -0000
http://www.cidrap.umn.edu/cidrap/content/influenza/general/news/feb0808flu.html
CDC says influenza B strain doesn't match vaccine
Lisa Schnirring Staff Writer
Feb 8, 2008 (CIDRAP News) - The US Centers for Disease Control and
Prevention (CDC) said today that most circulating influenza B viruses tested
so far this season don't match this year's vaccine, signaling that two of
the three vaccine components are off-target.
Joe Bresee, MD, chief of epidemiology and prevention in the CDC's Influenza
Division, told reporters at a briefing today that 93% of the circulating
influenza B viruses analyzed so far belong to the Yamagata lineage, which
doesn't match the influenza B component of this year's vaccine. The B
component is a B/Malaysia/2506/2004-like virus, which belongs to the
Victoria lineage.
Because the Yamagata and Victoria lineages are distinct, the vaccine
provides little cross-protection for influenza B, he said.
The news of the mismatch between the influenza B strains closely follows
recent indications that a circulating influenza A/H3N2 subtype,
A/Brisbane/10/2007-like, doesn't match the vaccine. However, the CDC said
the Brisbane strain is a recent antigenic variant of the
A/Wisconsin/67/2005-like virus, a component of this year's flu vaccine.
Consequently, CDC director Julie Gerberding said this year's vaccine should
provide some cross-protection against the Brisbane strain, according to a
Feb 2 Associated Press report.
"Even when there is less than an ideal match, there is still some
cross-protection," Bresee said. "This is especially true for high-risk
populations. Getting a flu vaccine may reduce the risk of death or
hospitalization from the disease."
According to the CDC's most recent weekly flu report, for the week ending
Jan 26, US laboratories have characterized 197 flu viruses so far this
season. Of 43 influenza B viruses, 40 (93%) belonged to the Yamagata
lineage. Three (7%) belonged to the Victoria lineage.
Bresee said it's difficult for global health officials to predict what
strains will be prevalent in the next influenza season, because the
selection must allow enough time for vaccine production. World Health
Organization (WHO) officials meet next week to advise what three components
should be included in the northern hemisphere's 2008-09 seasonal flu
vaccine.
Despite the difficulties, he said the seasonal flu vaccine has been well
matched to the circulating strains in 16 of the last 19 seasons.
The US flu season started out slowly, but activity has increased sharply,
which is typical, Bresee told reporters. All states are now reporting
influenza activity, and 31 are reporting widespread outbreaks.
So far, one flu-related death in a child has been recorded, but it is likely
that five additional deaths will be added to the CDC tally within the next
few days, Bresee said. He said the CDC doesn't know yet if any of the
children who died of flu this year were coinfected with
methicillin-resistant Staphylococcus aureus (MRSA). The CDC recently urged
clinicians to be alert for coinfections, particularly with MRSA. In the last
flu season the number of pediatric flu deaths was moderately higher than the
previous season; 15 of 73 deaths involved MRSA coinfections.
"This reminds us all that influenza is a common disease and can be a severe
disease," he said.
The news about the influenza B mismatch is the latest in a string of unusual
findings about circulating flu viruses. In late January, the European Centre
for Disease Prevention and Control sounded a warning that some H1N1
influenza viruses in Europe were showing signs of oseltamivir (Tamiflu)
resistance. Yesterday the WHO reported that resistance has been found in 14
countries, 10 of them in Europe.
According to a WHO table updated yesterday, 8.4% (15 of 179) of the H1N1
viruses analyzed in the United States so far had the resistance mutation,
and 6.3% (8 of 128) Canadian isolates showed signs of oseltamivir
resistance.
H1N1 is the third flu subtype included in the seasonal vaccine. So far, the
H1N1 component in this year's vaccine seems well-matched to circulating H1N1
viruses, health agencies have reported.
Bresee said the CDC is watching the oseltamivir-resistant viruses very
closely and that investigators still don't know what caused the mutation.
--
Regards
Pat Gardiner
www.go-self-sufficient.com
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