Hello Jan, Sorry about this problem with granddaughter. She apparently has immune deficiency and needs work-up for immune system like immune globulins IgG, IgM etc as well as cellular immune system. She could be helped by externally administered combined immune globulins if this is the problem, to prevent repeated infections. You could also keep her away from other children and adults having minor infections with respiratory symptoms.
She may also benefit from correction of any anemia or calcium, vitamin D deficiency if detected on blood work.
The fact that father had chemotherapy in past for hodgkin's, does not matter in causation of her illness attacks.