A new study from Danish researchers finds that high-dose flu vaccines reduced the incidence of pneumonia- and influenza-related hospitalization (P&I), but there was no difference in death rates between recipients of high-dose and standard-dose vaccines. The study is published in the Journal of Infection. 

High-dose influenza vaccine (HD-IV), which contains four times as much hemagglutinin as standard-dose influenza vaccine (SD-IV), was designed to address lower protection from SD-IV in adults 65 and older. 

Older adults are the most at risk for flu-related complications, and HD-IV has been demonstrated to induce higher antibody responses and significantly reduce the incidence of laboratory-confirmed influenza among older adults in multiple randomized trials, the authors said. 

No difference in all-cause mortality 

In the current study, the authors conducted a meta-analysis of all studies reporting outcomes of HD-IV compared to SD-IV regarding P&I hospitalization, all-cause hospitalization, and all-cause death in adults 65 and older over at least one flu season since 2009. Overall, their analysis included 105,685 participants with a mean age of 66 to 85 years.

HD-IV recipients demonstrated a P&I hospitalization rate of 0.8%, compared to 1.1% in the SD-IV group, for an overall vaccine efficacy of 23.5% (95% confidence interval [CI], 12.3% to 33.2%). For all-cause hospitalization, 14.1% of HD-IV recipients experienced hospitalization during the follow-up period, compared with 15.2% of SD-IV recipients, resulting in a vaccine efficacy of 7.3%.

The fixed-effects model indicated no difference in overall treatment effect between HD-IV and SD-IV regarding all-cause death.

“The fixed-effects model indicated no difference in overall treatment effect between HD-IV and SD-IV regarding all-cause death,” the authors said. 

A preclinical study of a monovalent mRNA vaccine that targets the H5N1 avian flu clade circulating in multiple world regions is immunogenic and protective, researchers from the University of Pennsylvania and St. Jude Children's Research Hospital reported today in Nature.

The team's goal was to develop tailor-made vaccines matched to flu strains that have high pandemic potential. They first reported those findings in a preprint study in April 2023.

In mice, the vaccine prompted a robust antibody response, and the antibodies neutralized different 2.3.4.4b clade viruses. Experiments on ferrets showed similar results, and the group's challenge studies in ferrets found the vaccine protected the animals from disease and death.

Scientists working on more closely matched version

Scott Hensley, PhD, professor of microbiology at Penn Institute for Immunology and one of the study authors, said on X today that the team is producing updated versions of the vaccine that more closely matches slightly drifted strains circulating today. 

At a briefing yesterday, federal health officials said discussions are still underway with mRNA vaccine makers Pfizer and Moderna. An announcement is expected soon on how they might be involved the development of vaccines against H5N1.

An imported avian flu case involving an Australian child who contracted the virus in India involves the South Asian 2.3.2.1a clade that is known to circulate in birds in India and Bangladesh, two researchers from the University of New South Wales reported today, based on data from GISAID, the Global Initiative on Sharing All Influenza Data.

The clade is different than the 2.3.4.4b clade spreading globally in birds, with occasional spillovers into animals and humans. The South Asian clade is also distinct from an older clade known as 2.3.2.1c that is circulating in poultry Cambodia and Vietnam, also with rare jumps to humans.

Tests reveal H7N3 in recent Australian high path poultry outbreak

In another Australian avian influenza development, Agriculture Victoria said today that it has confirmed highly pathogenic H7N3 as the cause of poultry deaths in an outbreak at a layer farm near Meredith. 

Officials said illnesses in humans who have contact with sick animals are possible, but the overall threat is low.

The department has imposed poultry movement restrictions in the area near the outbreak farm, and it urged bird owners to double down on their biosecurity measures.

An international group of experts led by the Yale School of Public Health has proposed adding two sub-classifications to the current dengue virus (DENV) nomenclature to help identify and track strains of potential epidemiologic or clinical importance.

The proposed additions, published on the preprint server medRxiv, split the current genotypes of the mosquito-borne virus into "major" and "minor" lineages to provide more spatiotemporal details, offer ways to assign lineages to sequence data, and propose new lineages.

DENV "is currently causing epidemics of unprecedented scope in endemic settings and expanding to new geographical areas," they wrote. "It is therefore critical to track this virus using genomic surveillance. However, the complex patterns of viral genomic diversity make it challenging to use the existing genotype classification system."

Additions may improve inter-group communication

On a website, the researchers describe their classification assignment tool and how to use it. They also updated the viral genotype definitions to reduce the number of genomes that are unassigned or amorphously categorized as "related."

It is imperative to have a precise and common language to monitor continued DENV transmission in different spatio-temporal scales; and that this is communicable to clinicians and public health officials who may not have a background in genomics.

The team said the added major and minor lineages will aid country- and research group–level discussions of relevant dengue virus diversity.

"With the implementation of interventions (e.g. vaccines, Wolbachia-infected mosquitoes) that may eventually select for specific viral lineages, it is imperative to have a precise and common language to monitor continued DENV transmission in different spatio-temporal scales; and that this is communicable to clinicians and public health officials who may not have a background in genomics," the study authors wrote.

"Moreover, the proposed lineages are robust to classification using partial genome sequences," they added.