Flu Scan for Sep 27, 2018

Flu vaccine protection in seniors
Bivalent avian flu vaccine in poultry

UK study: High flu vaccine uptake in seniors but modest protection

Flu vaccine uptake in UK seniors has been high in recent flu seasons, but vaccine effectiveness (VE) has been modest in this age-group and the vaccine has been ineffective against the most severe strain, according to a study today in Eurosurveillance.

Experts with Public Health England and elsewhere in the country assessed data from the 2010-11 season through 2016-17. The found that vaccine coverage was 64% in 65- to 69-year-olds, 74% in 70- to 74-year-olds, and 80% in people aged 75 and older.

Overall VE was 32.5% across the seven seasons against lab-confirmed influenza. By subtype, the vaccine was 60.8% effective against H1N1 and 50.5% against influenza B viruses but only a statistically non-significant 5.6% against H3N2, the strain that typically causes the most severe disease. In addition, VE was statistically significant only in 65- to 74-year-olds, among whom flu VE was 45.2%. VE was -26.2% in those aged 75 to 84 and -3.2% in people 85 and older.

The researchers also found a flu-related mortality rate of 74.9 per 100,000 population in people 75 and older, compared with 9.3 per 100,000 in those aged 65 to 74.

The authors conclude, "We found that despite achieving very high influenza vaccine uptake in those aged 65 years and older, the average annual age group-specific influenza-associated mortality risk in England was highest in those aged 75 years and older over a six-season period and during seasons dominated by circulation of influenza A(H3N2)."
Sep 27 Eurosurveill report


Study: Bivalent avian flu vaccine tied to less H7N9 in Chinese poultry

A surveillance study involving poultry farms and markets in China before and after the country launched a new bivalent H5/H7 vaccine to protect poultry in September 2017 found that the prevalence of H7N9 viruses dropped dramatically after the vaccine was introduced.

The Chinese researchers, however, found some worrisome evidence that some H7N9 viruses have acquired genes from duck influenza viruses and have adapted to ducks, which could spread the virus more widely, given that domestic ducks are raised in open fields where they can mix with other species and spread the virus to other locations.

Writing in Cell Host and Microbe today, the researchers collected 53,884 poultry samples across the country from February 2017 to January 2018. In total, they found 252 low-pathogenic H7N9 viruses, 69 highly pathogenic H7N9 viruses, and 1 highly pathogenic H7N2 virus. Of the viruses, 2 low-pathogenic and 14 highly pathogenic strains were collected after bivalent vaccine introduction. The highly pathogenic H7N9 viruses fell into nine genotypes, one of which is predominant, widespread, and highly virulent in mice. The investigators also found that some of the H7N9 and H7N2 viruses carrying duck genes that were lethal in ducks.

Vaccination coverage was much lower at farms raising fast-growing meat chickens, where some only used the previously purchased H5 vaccine. However, coverage was 73.1% at layer farms and those raising slow-growing meat chickens.

The team concluded that the vaccine played an important role in cutting H7N9 levels in poultry and likely prevented the sixth wave of human illness, during which only three cases were reported. The authors added that although the duck-adapted viruses were found in Fujian province, the findings raise new challenges to controlling avian flu in China, and they say one option may be applying the bivalent vaccine to ducks.
Sep 27 Cell Host Microbe abstract

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