Flu Scan for Oct 02, 2018

Flu ebb in Southern Hemisphere
High-dose flu vaccine in seniors

Flu shows signs of decline in some Southern Hemisphere regions

As the Southern Hemisphere's flu season winds down, disease levels in temperate South American and southern Africa countries decreased or have peaked in recent weeks, according to the latest global flu update from the World Health Organization (WHO).

In Australia, flu activity rose over the last month but still remained low, with levels in New Zealand remaining below the seasonal threshold. In recent weeks southern Africa experienced a second wave of flu activity, with influenza B the most commonly detected virus.

Elsewhere, some parts of South and Southeast Asia reported increasing flu activity, including India and Laos, both of which are reporting mainly 2009 H1N1 detections, and Thailand, which is reporting cocirculation of both influenza A viruses—H1N1 and H3N2.

In the Caribbean and Central America, flu activity remained low except in Haiti, El Salvador, and Nicaragua.

Globally, of flu viruses that tested positive during the first half of September, 84.4% were influenza A. Of subtyped influenza A viruses, 65.3% were 2009 H1N1 and 34.7% were H3N2.
Oct 1 WHO global flu update


Study: High-dose vaccine may offer advantages for seniors

The high-dose flu vaccine provided better protection against influenza hospitalization for seniors than the standard vaccine, according to a new study that matched study by age and residence.

To compare the vaccines, researchers from the Oregon Public Health Division examined immunization registry records and hospitalizations for lab-confirmed flu in the Portland area during the 2016-17 flu season. They published their findings yesterday in Vaccine.

Based on earlier studies comparing vaccines, they noted that the "healthy vaccine" phenomenon can inflate vaccine effectiveness (VE), while an "at-risk vaccinee" bias can deflate VE estimates. As another way to compare the two vaccines, they measured how they performed in groups matched by age, gender, residence type, race-ethnicity, provider bias, and zip code.

The first simple aggregate comparison of the two vaccine groups showed no added effectiveness against flu-related hospitalization. However, adding different categories increased VE, with the final analysis of 23,712 matched pairs suggesting that the high-dose vaccine was 30.7% more effective in preventing flu-related hospitalization (95% confidence interval, 8% to 48%).

The team suggested that VE studies include matching factors that reflect local geographic areas, age, and other potential provider biases. "As a caution, calculating vaccine effectiveness based on aggregate, non-matched methods from large datasets likely will produce distorted results and should be avoided," the authors wrote.
Oct 1 Vaccine abstract

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