Study: Ferrets given seasonal flu shot had worse H1N1 illness
In a study designed to shed light on a phenomenon seen in Canada of increased risk of pandemic 2009 H1N1 flu in those who received a flu vaccine the year before, ferrets given a seasonal flu shot had worse H1N1 disease than those who had not received the vaccine.
Writing in a study published yesterday in PLoS One, Canadian and Dutch researchers vaccinated 16 ferrets with the pre-pandemic trivalent (TIV, or three-strain) 2008-09 seasonal flu vaccine and 16 ferrets with a placebo. Seven weeks later they inoculated all animals with the 2009 H1N1 virus.
The investigators found that, beginning 2 days after H1N1 challenge, vaccinated animals had greater loss of appetite and weight than placebo animals. The ferrets reached their greatest between-group difference in weight loss relative to baseline 5 days post-challenge.
In addition, vaccinated ferrets had higher lung virus titers and greater lung inflammation 5 days post-challenge. All animals had recovered by 14 days after H1N1 challenge.
The authors conclude, "While they cannot be considered conclusive to explain human observations, these ferret findings are consistent with direct, adverse effect of prior 2008-09 TIV receipt on A(H1N1)pdm09 illness."
Jan 27 PLoS One study
Worldwide flu activity low in some areas, beating baselines in others
As flu activity remains high in North America and China, Europe is just beginning its flu season and levels remain low in most other areas, according to an update yesterday from the World Health Organization (WHO). The large majority (91.6%) of specimens tested from 72 countries worldwide are influenza type A, which includes 2009 H1N1 and H3N2.
The predominant strain in North America is 2009 H1N1, unlike last season when H3N2 was seen most often. In the United States, the proportion of outpatient visits for influenza-like illness (ILI) was 3.6%, above the 2.0% baseline. Deaths from pneumonia and influenza are above baseline, and the proportion of intensive care unit admissions among hospitalized flu patients is 19.4%, higher than any of the past three flu seasons.
Canada is seeing a larger proportion of flu cases this season among 20- to 64-year-olds than among those over 65, a pattern unlike last year.
Both 2009 H1N1 and H3N2 strains are being seen in Europe, with a modest propensity toward the latter (45% vs 55%); predominance depends on the country, but visits for ILI and acute respiratory infection remain low so far, the report says.
H3N2 activity is increasing in Iran and Turkey, as is 2009 H1N1 activity in Egypt. In other areas of northern Africa and central Asia, flu activity remains low. China is seeing an increase in activity, with both 2009 H1N1 and H3N2 dominant in the south and the former dominant in the north. The proportion of patients visiting physicians for ILI in South Korea stands at 27.3%, far above the 12.1% baseline.