I know you had mixed feelings about your husband having the Rituxan infusions because it does weaken the immune system’s response. But it really is vital to treating your husband’s cancer. Unfortunately, as with any cancer or cancer treatment it can leave the patient immuno compromised.

Regarding the high dose flu vaccine for your husband, that’s a question only his oncologist can answer. From my own personal experience with being immunocompromised, I’ve been asked by my transplant doctor to keep up to date on all vaccinations, which I have. But it’s not been suggested to have a booster shot for the high dose flu vaccine.

So I’d ask his doctor. If they recommend the flu vaccine and a booster, go with it. Even if it isn’t a full immunity, the vaccine will most likely create some antibodies which can go a long way in fighting the flu if your husband gets exposed.
Of course, it is really important for him to wear a mask anytime he’s out in public, groups of people at church or family events. Not just for Covid. Even a simple cold can get more complicated when our immune system is impaired. It comes with the territory, I’m sorry to say.

Have your husbands blood tests shown any improvement in the over abundance of B-Cells after the Rituximab?