'Tis the Season: Challenges and Opportunities of the Flu Vaccine

Every year there is talk about a universal flu vaccine that will be effective at preventing all strains of the virus, but two mechanisms make this a difficult task: antigenic drift and antigenic shift.

Antigenic drift describes the mutations of influenza virus genomes, leading to new strains of the virus that our immune systems have never encountered. Antigenic shift describes the ability of flu viruses from other species, such as swine and avian, to infect humans, which is the cause of most flu pandemics.

So what are scientists to do to battle these unpredictable changes in the flu virus?

Current Treatments and Limitations

Neuraminidase inhibitors (NAIs) are currently the only antivirals recommended to treat influenza virus infection. However, NAIs should be given within two days of noticing flu symptoms, which provides a very narrow window for treatment. Humans can also build a resistance that can spread through the population.

Scientists are actively pursuing alternative anti-influenza virus drugs that are more effective, can be administered later in the disease progression, and will not be as susceptible to viral resistance.

New Flu Treatments on the Horizon

Monoclonal Antibodies

• Targeting the stem region of the HA molecule
• Several in current clinical trials
• Demonstrated abilities to inhibit pulmonary viral load, control viral shedding, and lower patient symptom scores
• Stronger pharmacokinetics and longer therapeutic window than NAIs

RNA Polymerase Inhibitors

• Antiviral drug Favipiravir completed phase III trials
• Inhibits RNA-dependent RNA polymerase
• Effective in reducing viral titers and host mortality in mice models
• Promising candidate for broad acting anti-influenza therapy
• Also active against several other viruses

Epithelial Cell Therapies

• Focus on preventing epithelial cell death, which has a major impact on respiratory function following flu infection
• Fludase has been shown to remove 90% of sialic acid within 15 minutes of treatment
• Phase II trial showed patients tolerated treatment well with decreased viral load and shedding

Anti-influenza T cells are vital in researching influenza vaccines and treatments.

Flu Season by the Numbers

• About 1 billion people are infected with the flu every year
• Fewer than 50% of Americans got the flu shot in 2016-2017
• Average adult will be infected with the flu twice each decade of their lifetime

This post originally appeared on the Astarte Biologics blog and has been modified for Patch.