flu jab = flu injection?

Context:
There was nothing the doctors could do except monitor her condition and prescribe steroids to boost her blood count. A bone marrow transplant was possible, but it only had a very slim chance of working.

She said: ‘The whole family had to have flu jabs and keep away from me if they had a cold or infection as my immune system was so low.

'Without a cure for this disease, even the slightest knock or cut could lead to me having to go to hospital. I was terrified. I couldn’t go riding any more in case I fell. And every time my gums started bleeding I worried that I would bleed to death.