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Flu News Friday 7/23/21

Read the latest on influenza vaccines in this week’s roundup.

This digitally-colorized negative-stained transmission electron microscopic (TEM) image depicts a number of influenza A virions. Content Providers: CDC / F. A. Murphy

The Latest in Influenza Vaccines

Conference Announcement: The Eighth ESWI Influenza Conference is December 4th to 7th, 2021. Join colleagues and peers from around the world in Salzburg for the largest conference dedicated to influenza, RSV disease and Covid-19. Register here. Abstracts are due September 3, 2021; submit abstracts here.

The continued circulation and mutation of SARS-CoV-2 and the imminent threat of pandemic influenza are significant health security threats. Vivaldi Biosciences announced positive preclinical results for its combination UIV-SARS-CoV-2 vaccine. Delta-19 is an intranasal vaccine designed to provide protection against SARS-CoV-2 and all strains of influenza — potentially providing universal protection against all influenza A and B virus strains, including drifted seasonal influenza strains and emerging strains with pandemic potential. In a ferret model, the vaccine demonstrated prevention of SARS-CoV-2 viral replication in the upper respiratory tract, while elicitation of spike-specific antibodies was observed in 100% of the ferrets. The Delta-19 vaccine builds upon their work on a universal influenza vaccine; the UIV candidate has already shown potential in phase 1 and 2 clinical trials.

COVID-19 vaccines arrived faster than any before. In the race to develop those vaccines lies lessons for preventing future global outbreaks — including the inevitable return of pandemic influenza. This article discusses key lessons drawn by vaccine researchers, policymakers, and global health security experts to offer a path forward.

Scientists examined the immune responses of two inactivated influenza vaccines, a microneedle patch vaccine and an injected vaccine. While the hemagglutinin inhibition (HI) titers and antibody responses were similar among the vaccines, the microneedle vaccine exhibited higher neuraminidase inhibition (NI) titers, a larger proportion of circulating T follicular helper cells, and dose-sparing effects. Administered by placing the vaccine as a patch on the skin, transdermal patch vaccines could be an attractive alternative to injections for their ability to be more feasible in lower-resource settings and culturally sensitive.

A history of influenza exposure and infection contributes to immunological memory when encountering future influenza viruses, playing a role in protection. Known as immune imprinting, this lifelong bias was studied in the context of the two Influenza B virus lineages cocirculating in humans, B/Victoria and B/Yamagata, to account for the differing age distributions of cases and the resulting protective outcomes. The study findings suggest that the contrasting age distributions are driven by “historical changes in lineage frequencies combined with cross-protection between strains of the same lineage and additional protection against B/Yamagata in people first infected with it.”

Highly pathogenic avian influenza viruses (HPAIs), such as H5N1, are influenza viruses of zoonotic (non-human) origin that have caused severe infection. Human immune systems consider HPAIs to be novel because most do not have pre-existing immunity against them. If an HPAI strain evolves enough to have sufficient human to human transmission, there is concern for pandemic potential. Scientists designed an H5N1 self-assembled chimeric nanoparticle (cNP) vaccine. In a mouse model, the vaccine elicited an antibody response, demonstrated cross-reactivity against H5N6 and H5N8 strains, and cross-protection against homologous and heterologous flu viruses. The results suggest the use of cNP in influenza vaccines could be helpful for conferring broadly protective immunity.

Scientists studied the effect of Influenza A H5 subtype exposure from vaccination on future vaccination with the same subtype (homologous prime-boost regimen) or with a different subtype (heterologous prime-boost regimen). It was found that H5-specific antibodies elicited by boosting are “highly correlated with the antigenic similarity between the priming and boosting H5 vaccine strains.” Scientists concluded that within the context of H5 vaccination, hemagglutinin (HA) imprinting was observed.

Vaccination failure is when an individual does not develop a sufficient immune response to initial vaccination for a particular disease and contracts an infection; it is often measured through correlates of protection. In a mouse model, scientists identified a mechanism in which influenza infection directly diminishes the adaptive immune system, to account for vaccine failures and reduced efficacy during influenza seasons. The findings demonstrated that infection with the virus generates a suppressed immune state through preferentially attacking activated immune cells, even in previously immune or vaccinated individuals.