Where Can I Get an mRNA Flu Shot?

— There's limited availability, largely because of late FDA approval

For those who want to try the new mRNA flu shot (mFlusiva) this season, tracking it down might take some work, experts said.

Moderna's shot was only approved in Augustopens in a new tab or window, for all adults ages 50 and older, long after national retail pharmacy chains had placed orders for their supply of this year's flu shots. Questions about demand also linger.

So it's not surprising that the mRNA shot will be available in limited quantities this year, Amesh Adalja, MD, of the Johns Hopkins Center for Health Security in Baltimore, told MedPage Today.

A Moderna spokesperson confirmed that the company planned a "limited launch in year one," but noted that the shot is available "at more than 13,000 locations," and provided MedPage Today with a link to the company's vaccine finderopens in a new tab or window.

"If someone wants to get mFlusiva, they're going to have to use that website or call around," Adalja said.

He compared it to the early days of Flublok -- his preferred vaccine -- when he would have to call around different pharmacies to track it down.

"It used to be harder to find Flublok and Flucelvax, which are more novel flu vaccines, because drugstores order the standard one and they don't differentiate the products, which is a problem," Adalja noted.

There are a lot of options when it comes to flu shots. There are a handful of standard-dose products, and they're made by growing the influenza virus in eggs. Brand names include Fluzone, Fluarix, FluLaval, and Afluria.

There's also FluMist, which is an egg-based, live-attenuated nasal spray vaccine.

Then there are "enhanced" products, including the recombinant shot Flublok, which contains three times the antigenopens in a new tab or window of standard-dose vaccines, and the cell-based shot Flucelvax. Both of these are egg-free.

Other enhanced flu shots include Fluzone High-Dose and the adjuvanted shot Fluad, both of which are made in eggs and approved for people ages 65 and up. And now, there's the mRNA shot.

Notably, all flu shots in the U.S. are now trivalent, since the CDC said thatopens in a new tab or window the B/Yamagata lineage stopped circulating after March 2020.

Choosing among these vaccines is partly patient preference, and Adalja has his own favorites: "When someone asks me which flu vaccine to get, I basically say Flublok or mFlusiva are the two best flu vaccines to get right now."

That's based on his read of the data, and he acknowledges there aren't good head-to-head studies of the mRNA shot versus other enhanced vaccines in terms of clinical outcomes. Indeed, one of the key complaints about Moderna's pivotal phase III study was that it compared mFlusiva with a standard-dose vaccineopens in a new tab or window.

When the FDA approvedopens in a new tab or window the mRNA flu shot this summer, it gave traditional approval in adults ages 50 to 64, but accelerated approval for those 65 and older, with a postmarketing effectiveness study -- ideally against an enhanced vaccine -- planned for that population.

That compromise was reached after the FDA, under former vaccine director Vinay Prasad, MD, MPH, initially refused to reviewopens in a new tab or window Moderna's application for the vaccine over concerns about the lack of a better comparator. A week later, the agency reversed its decisionopens in a new tab or window.

A separate phase III study did show that the mRNA shot led to greater immunogenicity than Fluzone High-Doseopens in a new tab or window in those ages 65 and up, but it did not examine clinical outcomes.

"The immune response elicited by the mRNA vaccine seems to be superior in some respects ... but it remains to be seen whether that translates into better protection," said William Schaffner, MD, of Vanderbilt University in Nashville, Tennessee, who is also a spokesperson for the Infectious Diseases Society of America.

He noted that the mRNA shot has greater reactogenicity than standard flu shots, "and I would anticipate that would also be true for the enhanced vaccines." This includes higher rates of injection-site pain, fatigue, headache, and myalgia, according to data from the phase III trial.

"That is something people have to weigh," Adalja said. "When you look at the comparative efficacy, you've got to say, is it worth the extra reactions that you get for the added protection?"

That may be especially off-putting for healthcare workers who don't want to miss a shift because of a vaccine reaction. On the other hand, Schaffner said, the adaptability of the mRNA platform may be a boon to healthcare workers, as it could theoretically deliver a vaccine that's more closely matched to the circulating strain.

FDA finalizes strain selection in Marchopens in a new tab or window, but with newer technologies -- including the cell-based and recombinant vaccines, as well as the mRNA vaccine -- that timeline could potentially be shortened, Schaffner said.

That would be a heavier lift from a policy perspective, he added. "FDA and maybe even the WHO [World Health Organization] would have to adapt their recommendation framework."

Regardless of what the future holds, Schaffner emphasized that now is the time to get vaccinated -- and that patients shouldn't wait for "flu before boo" this year.

"Influenza has started early in many parts of the country," he noted. "If you have not been vaccinated, run, do not walk ... and get the vaccine that's available to you."