That's an interesting hypothesis.Here's a Scientific American article from April on the stunning drop in flu cases in the first year of the Covid pandemic. One interesting tangent is the flu vaccines are developed off of the previous year's virus, and because of such limited circulation, last year's may not have had the chance to mutate much, making this year's vaccines more effective.
"Because each year’s flu vaccine is based on strains that have been circulating around the world during the past 12 months, it is unclear how the upcoming 2021–2022 vaccine will fare should the typical patterns of infection return. The WHO made its flu strain recommendations in late February as usual, but they were based on far fewer cases than normal. Yet with less virus circulating, there is a reduced chance of mutation, so the upcoming vaccine could be especially effective."
Here's hoping! Imagine if we had a flu surge alongside Covid's next variants. Nightmare stuff, especially for those who live where they haven't had widespread access to the Covid vaxxes yet.
I've been wondering how social distancing, masking etc. did so much better at halting the flu than they did Covid, aside from Covid being much more contagious (possibly), even before the delta variant. It makes sense that with less opportunity for influenza A to mutate this past year, the vaccines would work better. Also, residual immunity from last year's flu might be greater. Most people don't get flu shots, so this might even be a bigger reason for last year's influnza being so light.
It is worrying, though, if the flu begins to mutate briskly again, and there is less immunity than normal next year, since so few got it this year. And folks without access to covid shots probably don't have access to flu shots either.
Wishing your husband the best! I've heard that a third booster can be helpful for people on immune suppressing drugs. I think my mom should get a third dose too, since she's on all kind of meds, some for her autoimmune disease. I haven't heard that anyone has recommended this to her yet, though.