Pursuing the Holy Grail

The holy grail of influenza vaccines is a flu vaccine that works year after year. That's called durable immunity.

Now, we get a new shot every year because flu strains change. Each year, scientists select three to four flu viruses to include in the annual vaccine. Most times, they get it right, but when they're off, we have a bad flu year.

In the US, a bad year can mean more than seven hundred thousand people hospitalized and fifty thousand deaths. Globally, six hundred thousand people can die in a bad flu year.

Flu vaccines now target two proteins on the virus surface, the Ha and Na, which the virus uses to enter our respiratory cells. But these proteins are always changing.

A small change is called a drift which reduces how well the vaccine works. A big change is called a shift and makes the vaccine much less effective.

Scientists have been looking for areas of the flu virus to target that don't shift or drift. What new studies have produced is an mRNA flu vaccine - like the COVID vaccine - that targets the stem of the Ha protein. This part doesn't change as often and could create longer immunity.

The vaccine is called H1ssF-3928 LNP and is entering Phase I clinical trials. Earlier studies showed positive results with these stem protein fragments.

If clinical trials are successful, this could be the end of yearly vaccines which is expensive and time consuming. But more important is how this approach could be protective against novel flu strains that threaten a new pandemic.

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