I found it quite plausible that Kakashi could get struck by the flu. Missions are stressful, sometimes especially on the body, (ANBU missions are almost defined by being extra-strenuous, when they aren't defined by being effectively "off the books" level secret, or are both) and while having his precious people largely alive has kept him from deliberately stringing as many intense missions back to back as possible why would any of them be keeping track of his vaccine dates to know to not let him miss it due to inconvenient mission scheduling? They're all a bit busy and he's an adult, technically and practically speaking. It's fairly common in older teens and young adults to start forgetting to keep up with yearly vaccines now that they aren't scheduled by their "responsible adult figures" unless there is a specific reason to be extra-vigilant (like me knowing my mother is somewhat immunocompromised and my grandmother moreso).
This is why things like chickenpox, which are natural vaccines against getting them again later and also a lot more dangerous to adult victims than children, are generally "prescribed" to be allowed to be caught naturally and suffered the once as a kid, than to deal with yearly vaccines that will be forgotten eventually- chickenpox can easily be lethal to an adult patient while a kid is usually just miserable for a while.
Plus Influenza has too many sub-strains and mutations and variables to ever get one catch-all vaccine, and thus requires yearly updates for everyone who can safely receive them, aimed at the "most likely" varieties year by year.
On that note, even with the vaccine sometimes a patient will catch a different strain than the ones that year's vaccine was aimed at, so even with the shot poor Kakashi could definitely have the luck to get the one it didn't help enough to block. (It would also explain part of why it didn't occur to him that he might have the flu instead of a cold, aside from his fuzzied out head.)

Plot holes can be patched up with liberal application of suspension of disbelief. A great oneshot nonetheless!

Ah, this is how it should have been :’)

It's totally not a plot hole because Kakashi is exactly the type to forget about shots or assume he's fine without them, then run himself down with overwork and catch things that lay him out worse than any enemy shinobi ever could.

Really well written, I adore little Naruto trusting Kakashi so much (and my heart melted at the Kakashi-nii!) and Minato and Kushina being alive and Naruto being cared for and Kakashi being part of the family, I AM EXPLODING FROM FEELS!

Good job! Please keep writing things!

wowowowow

Ah, very adorable!

So Cute!

Hi

Cute!

Nice story!
:D

This was very cute. Kakashi has a family. Ah, he should have known eh?
Nice writing!

"Kaka-nii..!" Enough said.
*I just had to say something for this kind of nice and sweet and wonderful AU, though, ah, bad flu* *You're very welcomed to write hundreds more in this 'verse thank you*

ULTIMATE AU FLUFFYNESS! (Yes, I spelled that wrong.)

naaw poor kaka-nii hope he gets better soon

This is SO cute!
I love Kakashi and Minato and KUshina and baby Naruto was a VERY nice touch!