FluMist comes in a small two-dose tube, and the vaccine is sprayed into each nostril similar to an anti-allergy spray. And you’re done. No need to inhale deeply or hold your nose.
This seems an obvious choice for children with an aversion to needles, and it’s free in NSW, Queensland and South Australia for kids under five. For older children – and everyone in Victoria – you’ll be out of pocket $49.95. About 400,000 doses are available through private pharmacies, AstraZeneca tells me, and I was able to find doses widely.
So, how does a nose-spray vaccine work? And does the clinical data on protection and safety stack up?
Does it work?
FluMist isn’t entirely new: America has had access since 2003, and Europe since 2011. Australia is getting access now because AstraZeneca has finally made a southern hemisphere-specific vaccine.
Luckily, that gives us lots of data to evaluate.
Science uses a “hierarchy of evidence” as certain types of evidence are more trustworthy than others.
At the bottom is expert opinion: what leading scientists or doctors think (the thoughts of non-experts, like your uncle Fred on Facebook, rank well below that).
At the top are meta-analyses: these combine several studies to provide a high-quality estimate.
This 2024 meta-analysis combined 19 randomised-controlled trials (the best-quality type of trial) to produce a comparative estimate of the effectiveness of FluMist versus the standard flu vaccine.
To read the results of a meta-analysis, you want to look for this graph, called a forest plot – allegedly named for its resemblance to a “forest of lines”, but you have to really squint to see a likeness.
Each row represents results from a single trial comparing FluMist (also known as live-attenuated intranasal vaccine or LAIV) with a standard flu vaccine (injectable influenza vaccine or IIV).
The key outcome is the “odds ratio” (OR): the odds of getting a confirmed case of influenza if you had FluMist versus the standard jab.
Three of the six studies found you were less likely to get the flu if you received FluMist (the top three), two found the opposite (the bottom two).
The blue polygon down the bottom is the combined weighted average of the study findings. By weighting the studies – allowing some to contribute more to the average than others – you can ensure the best studies contribute the most to the result.
“You’re weighting on precision. A really precise study, even if it’s not that big, will have a really big impact,” says Dr Gideon Meyerowitz-Katz, a statistics expert at the University of Wollongong.
You can see the weighted average sits almost in the middle: meaning the two vaccines are pretty similar in the protection they provide.
“It’s safe and effective, is the bottom line, and there’s real-world experience from the UK for quite a few years now showing it’s a useful vaccine,” says Professor Robert Booy, former head of clinical research at the National Centre for Immunisation Research and Surveillance.
How does it work?
With the top-line data out of the way, we can get a little bit nerdier.
Unlike the standard flu vaccine, FluMist uses a live version of the virus that is capable of getting into cells and replicating just as it would during an infection.
The trick here is the virus has been weakened, so it can only grow in colder environments – such as the inside of the nose.
Immune cells within the mucosal membranes of the nose recognise the virus and generate virus-specific antibodies – little bits of cellular gum, specially shaped to bind to viruses and jam up their machinery. Think of them as entrenched front-line defences, ready to attack.
This seems like a significant advantage of FluMist: you get antibodies in the place where the real virus is most likely to attack. Standard influenza vaccines instead generate antibodies in the blood, which is useful, but not on the front line.
FluMist also has a second advantage. Because the vaccine contains a live virus, it prompts our body to recruit powerful virus-busting T-cells capable of killing the virus, says Dr Cyra Patel, who led a review of the evidence for the vaccine for the National Centre for Immunisation Research and Surveillance.
But there are some trade-offs.
FluMist is more likely to cause a runny nose or sniffles, as opposed to the injection-site pain common from the standard vaccine.
And dealing with a live virus introduces additional complexity. Some years, one strain within the vaccine failed to replicate strongly in the nose, meaning less protection (the US pulled its recommendation for FluMist for several years after studies showed reduced protection).
Those issues seem resolved now though, says Patel. The best evidence is the vaccine is every bit as effective as the injectable variant – without needles.
“The data we have shows they are very, very similar in their effectiveness and their safety,” says Patel. “Really, it’s more or less the same.”
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Liam Mannix is an investigative journalist at The Age. Before that, he was national science reporter for The Age and the Sydney Morning Herald.
Contact him via email or Signal (encrypted) liammannix.18
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