Extolling The Virtues Of Flu Shots Even With A Mismatched Component
Posted by preparedcitizens on January 12, 2009
According to the CDC website the formulations for the 2008-2009 flu seasons for both the injectable and intranasal flu vaccine 2008-09 include protection against
- A/Brisbane/59/2007 (H1N1),
- A/Brisbane/10/2007 (H3N2), and
- B/Florida/4/2006 strains.
If you had influenza B Malaysia last year and a flu shot this year kudos to you, you may have the antibodies to resist this years circulating strain. Oddly enough, B/Malaysia/2506/2004-like virus was the 2007-2008 component.
A little bit about Influenza B viruses…Influenza B has a limited host range only infecting humans and seals. Influenza A viruses have a much greater host range. More about influenza B infection toward the end of this post.
Influenza B viruses also mutate by genetic drift and reassortment at a much slower rate (2 to 3 times slower) than A viruses. This is important because when they get the vaccine right, it will typically stay right for the entire flu season. Influenza A viruses are highly mutable so at the tail end of any flu season we are at more risk even though immunized.
What my response is: Non pharmaceutical interventions must also remain in the forefront of all of our efforts. And forced vaccinations of children or anyone else is not a guarantee of safety. It is an overreaction. Education and awareness are the best weapons in our arsenal.
So what is being discussed….
According to the website FluWatch Canada this is what is currently circulating in Canada:
December 28, 2008 to January 3, 2009 (Week 53)
Overall influenza activity in Canada remains low; an influenza outbreak in a hospital was reported in Ontario
During week 53, influenza activity in Canada remained low overall with the majority of the influenza surveillance regions still reporting no activity.
Sixteen regions (in BC, AB, ON & QC) reported sporadic influenza activity and localized activity was reported in 2 regions (central region in AB and in Toronto, ON) (see map).
Note that no data for 2 regions in SK were received this week. Eighty-seven specimens tested positive for influenza in Canada this week (percentage positive = 3.3%; 87/2,633) (see table).
The majority of influenza virus detections to date this season were influenza A viruses (54% or 165/304); however influenza B detections have slowly increased over the last several weeks.
In week 53, the ILI consultation rate increased to 23 ILI consultations per 1,000 patient visits (see ILI graph), however it remains below the expected range for this week. The sentinel response rate was low at 37%. An outbreak of influenza in a hospital in ON was reported in week 53.
Other Respiratory Viruses: RSV detections for Canada as a whole continue to increase while detections for adenoviruses and parainfluenza viruses remain at fairly low levels (see graph).
Antigenic Characterization:
Since 1 September 2008, the NML has antigenically characterized 33 influenza viruses:10 influenza A/Brisbane/59/2007(H1N1)-like (from BC, AB, ON & NS),
1 influenza A/Brisbane/10/2007(H3N2)-like (from BC),
3 influenza B/Florida/4/2006-like (from ON and AB) and
19 B/Malaysia/2506/2004-like (from ON and AB).
A/Brisbane/59/2007(H1N1), A/Brisbane/10/2007(H3N2) and /Florida/4/2006 are the influenza A and influenza B components recommended for the 2008-09 influenza vaccine.
****B/Malaysia/2506/2004 was the influenza B component for the 2007-2008 season vaccine
Regarding Antiviral Resistance, this was noted in Canada…
Results from the NML: (my note: National Microbiology Lab of Canada)
Since the start of the season, the NML has tested 11 influenza A isolates (6 H1N1 and 5 H3N2) for amantadine resistance. All of the H1N1 isolates were susceptible; however all of the H3N2 isolates were resistant to amantadine (resistance = 100% or 5/5). The resistant isolates were from ON, AB and BC.
The NML has also tested 24 influenza isolates (5 A/H1N1, 2 A/H3N2 & 17 B) for oseltamivir (Tamiflu) resistance. All of the A/H3N2 and B isolates were sensitive; however all of the A/H1N1 isolates were resistant to oseltamivir due to the H274Y mutation (resistance = 100% or 5/5). The resistant isolates were from NS, ON and BC.
All 22 influenza isolates (3 A/H1N1, 2 A/H3N2 & 17 B) tested for zanamivir resistance to date were sensitive to zanamivir.
Oseltamivir resistance findings from Provincial laboratories:
To date this season, 24 influenza isolates in BC have been sub-typed as A/H1 and were assessed genotypically for oseltamivir resistance using an SNP assay. Eighteen isolates tested positive for the H274Y mutation (resistance = 100% or 18/18), with the other 6 specimens still pending confirmatory testing.
Influenza-associated Paediatric Hospitalizations:
No laboratory-confirmed influenza-associated paediatric hospitalizations have been reported through the Immunization Monitoring Program Active (IMPACT) network for the 2008-09 season.
It is interesting to note that last flu season there was a mismatch to the circulating B strains. According to CIDRAP last year, “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.”
More on Seasonal Flu Activity around the world…
from the WHO
Seasonal influenza activity in the world, weeks 51-52 (as of 7 January 2008)
During the weeks 51-52, the overall level of influenza activity in the world began to increase in some countries in Europe. Ireland, Portugal and the United Kingdom of Great Britain and Northern Ireland reported widespread activity with influenza-like illness (ILI) above threshold levels. France also reported increased activity while regional activity was reported in the Netherlands, Spain and local activity in Italy. Activity in many other countries remained low. The majority of viruses identified this season have been influenza A (H3N2).
Ireland: Widespread influenza A activity has been reported.
Italy: Three influenza A H3N2 influenza isolates were reported during week 52.
Netherlands: In week 52 a substantial proportion of specimens from sentinel ILI patients contained influenza virus. To date all influenza viruses detected in specimens from sentinel ILI patients were A(H3N2).
Portugal: Widespread influenza A (H3N2) activity was reported.
Spain: Regional activity was reported. Influenza A (H3N2) viruses were detected.
United Kingdom of Great Britain and Northern Ireland: Influenza activity continued to be widespread across the country with GP consultation rates above the threshold levels in England and Scotland in week 52. The majority of the specimens have been positive for influenza A (H3N2), with low numbers of H1N1 and B detected.
Sporadic influenza activity was observed in Belgium (A), Cameroon (A, B), Canada (A,B), China (H1, H3, B), China Hong Kong Special Administrative Region (H1,H3,B), Finland (A,B), Germany (H1,H3, B), Greece (A) , Iran (H3), Israel (A;B), Japan (H1,H3, B), Latvia (A) , Luxembourg (A), Morocco (H1,B), Netherlands (H3), Norway (H1,H3,B), Russian Federation (H1,H3,B), Slovenia (H1,H3), Switzerland (H3), Tunisia (H1,B) and the United States of America (H1,H3,B).
Croatia, Czech Republic, Estonia, Greece, Lithuania, Malta, Poland, Romania and Serbia reported no influenza activity.
What is the difference to us between Influenza A infection, Influenza B infection and even Influenza C infection?
Influenza A can infect a wide range of hosts. Pigs, horses, cats, ferrets, wild birds, humans. This highly mutable virus is divided into subtypes and is named according to the two proteins on the surface of the virus – Hemagglutinin (HA) and Neuraminidase (NA). So when someone says H5N1 or H3N2 or H1N1 they are describing with specificity the two proteins that are in the Influenza A strain. There are 16 known HA subtypes and 9 known NA subtypes, not all infect humans. And currently only H1N1, H3N2 and H1N2 are circulating in humans. Rarely some of these subtypes cross the species barrier. H3N8, an influenza A virus that typically infects horses has recently infected dogs.
H5N1 is the subtype that scientists have their eyes on because it is crossing the species barrier from birds to humans, with other species also being infected from time to time. Only influenza A viruses infect birds. Some are low pathogenic and some are highly pathogenic. Of the H5 influenza A viruses there are nine subtypes. There are also nine know subtypes of the H7 influenza A virus. H7 infection in humans is a rare event. It is also broken down into high path. and low path subtypes. And then there is the H9 subtype which also has nine subtypes. This virus is only found in a low pathogenic form.
Pathogenesis:
Highly pathogenic or low pathogenic
Pathogenic means the ability to cause disease. A flu virus can be highly pathogenic or it can have low pathogenicity. A highly pathogenic flu virus can cause severe illness and death. A low pathogenic flu virus is much less likely to cause severe disease.
Typically H1, H2 and H3 subtypes are what have caused illness in humans. When each subtype first emerged it caused a human pandemic because people did not have antibodies to fight off the newly emerged subtype. This is what we are watching for with the H5 subtype. It is increasingly infecting more humans demonstrating that it is adapting to the human host.
An infection with an influenza A virus is pretty well known as to what we experience. It’s hallmark is high fever, cough, muscle aches, and frequently we develop secondary infections like pneumonia.
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Influenza B viruses as I mentioned above are found in humans and seals. Influenza B viruses are not classified by subtype. They typically cause less severe epidemics than Influenza A and they do not cause pandemics.
Infection with a B virus usually causes less severe symptoms but it is still nothing to take lightly. Influenza B does have the potential to cause more severe disease in older persons and the very young.
Influenza C virus causes mild respiratory illness and is not thought to cause epidemics.
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So what is circulating in the US right now?
2008-2009 Influenza Season Week 53 ending January 3, 2009
Antigenic Characterization:
CDC has antigenically characterized 110 influenza viruses [68 influenza A (H1), 13 influenza A (H3) and 29 influenza B viruses] collected by U.S. laboratories since October 1, 2008.
All 68 influenza A (H1) viruses are related to the influenza A (H1N1) component of the 2008-09 influenza vaccine (A/Brisbane/59/2007). All 13 influenza A (H3N2) viruses are related to the A (H3N2) vaccine component (A/Brisbane/10/2007).
Influenza B viruses currently circulating can be divided into two distinct lineages represented by the B/Yamagata/16/88 and B/Victoria/02/87 viruses. Nine influenza B viruses tested belong to the B/Yamagata lineage and are related to the vaccine strain (B/Florida/04/2006). The remaining 20 viruses belong to the B/Victoria lineage and are not related to the vaccine strain. Seventeen of the 20 viruses belonging to the B/Victoria lineage were from two states.
Data on antigenic characterization should be interpreted with caution given that:
- Few U.S. isolates are available for testing because of limited influenza activity thus far.
- The majority of viruses antigenically characterized to date come from only three states and may not be nationally representative.
- Antigenic characterization data is based on hemagglutination inhibition (HI) testing using a panel of reference ferret antisera and results may not correlate with clinical protection against circulating viruses provided by influenza vaccination.
Annual influenza vaccination is expected to provide the best protection against those virus strains that are related to the vaccine strains, but limited to no protection may be expected when the vaccine and circulating virus strains are so different as to be from different lineages, as is seen with the two lineages of influenza B viruses.
In other words….A flu shot for the 2008-2009 Flu Season is still a very good idea. And in the case of H5N1 causing a pandemic during this flu season (along with seasonal flu) the N1 component of the flu shot may offer us a little bit of benefit against the N1 part of H5N1. I will take any advantage I can get. We can do the best we can to avoid getting the flu by becoming aware of what it is that is circulating throughout the entire flu season, knowing what strains we have been vaccinated against (if that was our decision) and to keep our hands away from our mucous membranes. There is so much that we don’t know about the world of virology and infectious disease control, but there are some things that we do know. Let’s make the best use of what we do know in order to keep as many people safe and healthy as possible.
Resources:
Respiratory Virus Detections/Isolations in Canada – Quite a document!
DemFromCt is currently writing a three part series about the complicated nature of what we are dealing with. Dem is a good friend (for a Democrat :-) ). He is an excellent writer and can really explain much better than I can the ins and outs of all of this. His series is called “Flu and You” part 1 is here.
Mike at Avian Flu Diary has great information and he quotes medical writer extraordinaire Helen Branswell.
