Scientists have been on the hunt for a universal influenza vaccine for decades, but thus far, none has yet materialized for human use. That's unfortunate, because one is desperately needed. Between 12,000 and 56,000 Americans die from the flu and associated complications each year, and in the most recent season, the death toll skyrocketed to 80,000. Yearly vaccination prevents an average of 4.3 million flu illnesses each year, but that number could be much higher.

The difficulty in battling seasonal flu owes to the disease's diversity. There are numerous strains and types of influenza virus and their prevalence differs each year, forcing health officials to predict what strains to vaccinate against. When their predictions are correct, the flu vaccine is more efficacious. When they're wrong, it is less effective.

A universal flu vaccine could finally end this inefficient guessing game. According to the National Institutes of Health, such a vaccine should be 75% effective, protect against group I and group II influenza A viruses (the most common to infect humans), last for at least one year, and be suitable for all age groups.

In 2013, then U.S. Food and Drug Administration (FDA) Chief Scientist Jesse Goodman predicted that that the earliest we'd see such a vaccine was in five to ten years.

Fulfilling his estimate is a new potential "vaccine" candidate described in today's issue of the journal Science. Nick S. Laursen of the Scripps Research Institute and his colleagues manufactured a treatment using antibodies – proteins that neutralize invading pathogens – from llamas that protected mice against numerous strains of influenza virus, including influenza A and B viruses, the two types to which humans are susceptible. *Laursen's treatment is technically not a vaccine, but the effects are similar. A vaccine infuses a host with weakened or killed viruses, allowing their immune system to produce its own antibodies. Instead the treatment simply inserts the antibodies directly.

Why llama antibodies? Turns out, the fluffy, adorable camelids evolved antibodies that have the smallest binding sites of any known antibody. This allows llama antibodies to attach to a wide variety of disease antigens. Moreover, llama antibodies are exceptionally stable and easy to produce compared to other antibodies.

In their study, Laursen and his colleagues compared their llama-derived "vaccine," called MD3606, to another universal flu vaccine candidate. They found that the llama-derived treatment, which was administered nasally, saved many, many more mice from a wide variety of flu infections. What's more, it could be administered at much lower doses and it became effective in just three to seven days. Protection from the current flu vaccine in humans takes two weeks to kick in.

The current study is preliminary and must be replicated in human trials, which could take years. However, its hopeful results are unprecedented in the long hunt for a universal flu vaccine. As the researchers wrote:

"An annual intranasal administration... may provide passive protection for the entire influenza season... The rapid onset of protection, together with the unprecedented cross-reactivity of MD3606 to avian influenza strains, also offers the possibility of using this approach as a prophylactic immediately upon onset of an influenza pandemic..."

Source: Laursen et al. "Universal protection against influenza infection by a multidomain antibody to influenza hemagglutinin." Science. 2 NOVEMBER 2018 • VOL 362 ISSUE 6414

*Section added 11/1