FLU NEWS SCAN: Novel flu C virus in pig, flu vaccine effects in elderly, H1N1 adjuvant scrutiny

Feb 8, 2013

Study: Oklahoma pig virus represents new influenza C subtype
An influenza virus that was recently identified in a sick pig in Oklahoma represents a new subtype of influenza C and suggests the possibility that type C viruses can evolve more rapidly than previously supposed, potentially posing an increased threat to humans, according to a report published yesterday in PLoS Pathogens. Flu C viruses, previously known to exist in only one subtype, occasionally cause illness in children, but cases are much less common than with A and B viruses. The researchers, from Minnesota, South Dakota, and Tennessee, isolated an orthomyxovirus from a sick pig and determined that it had seven RNA segments with about 50% overall identity to human flu C viruses. A phylogenetic analysis revealed that the degree of difference between this virus, dubbed C/OK, and human flu C viruses was similar to that between human flu A and B viruses. Antibody testing showed little cross-reactivity between C/OK and human flu C viruses. The new virus was able to infect both pigs and ferrets and spread to other animals by direct contact. The authors say their findings suggest that C/OK heralds a new flu C subtype. "This is significant, as co-circulation of multiple subtypes of influenza allows for rapid viral evolution through antigenic shift, a property previously only shown for influenza A viruses," they write. "The ability of C/OK to infect ferrets along with the absence of antibodies to C/OK in humans, suggests that such viruses may become a potential threat to human health."
Feb 7 PLoS Pathog report
Dec 7, 2012, CIDRAP News story on flu C cases in children

Study suggests vaccine not protecting elderly Danes against influenza A
Danish researchers say it appears that this year's flu vaccine has given elderly Danes (65 and older) little or no protection against influenza A, probably in part because of mutations in the circulating strains. Their report in Eurosurveillance says flu activity has been high in elderly Danes this season, and A/H3N2 strains have accounted for 93% of isolates. Using national microbiology and vaccination databases, the authors collected test results and vaccination status on elderly people who were tested for flu from Oct 1, 2012, to Jan 27, 2013. Of 1,443 people who were tested, 364 were positive for influenza A and 35 for flu B. Those who tested negative were used as controls. Vaccination coverage was 45% among the cases and 41% among the controls. On this basis, vaccine effectiveness (VE) against flu A was estimated at -11% (95% confidence interval [CI], -41% to 14%), while VE against flu B was 69% (95% CI, 26% to 87%). Genetic studies of circulating H3N2 viruses revealed genetic drift, with seven mutations at key antigenic sites, which may help explain the low VE, the report says. The authors note that they couldn't adjust for comorbidities in the patients but did adjust for related factors such as age-group. "Elderly people who are tested for influenza may represent a more vulnerable group, who have a weaker response to vaccination compared with the elderly population in general; however, if this would explain the findings, we would also expect a low VE against influenza B," they write. They note that early estimates of overall, all-ages VE in some other countries this season have ranged from 45% to 55%.
Feb 7 Eurosurveillance report

Researchers suspect role of Pandemrix adjuvant in narcolepsy cases
The adjuvant in Pandemrix, GlaxoSmithKline's (GSK's) 2009 H1N1 vaccine, is among the ingredients under close scrutiny by researchers around the world for a possible role in the vaccine's link to cases of narcolepsy in kids in Finland, Sweden, and Ireland, Reuters reported today. The immune-boosting adjuvant, AS03, is also in a GSK H5N1 pandemic flu vaccine that a US Food and Drug Administration panel recommended in November for approval as a stockpiled vaccine, possibly paving the way for the first US approval of an adjuvanted flu vaccine. "The adjuvant in the Pandemrix vaccine is very potent and we think it may have played a role," said Markku Partinen, MD, PhD, a neurologist at the Helsinki Sleep Clinic who is investigating the vaccine-narcolepsy link. Outi Vaarala, MD, PhD, of the Immune Response Unit at Finland's National Institute for Health and Welfare says her group has found that the way antibodies from Pandemrix-vaccinated children bind to the virus antigen differs from what happens with a Canadian-made version. Others take a more cautious approach. Tomas Salmonson, MD, an official with the European Medicines Agency, which licenses Pandemrix, said, "We may speculate that this specific antigen together with a very potent adjuvant could be the cause for all this. But that's only one of several possible explanations."
Feb 8 Reuters story
Nov 15, 2012, CIDRAP News story on H5N1 vaccine

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