I don't know if anyone will even know the answer to this.
I was just reading that the flu vaccine will be rolled out to all 2 and 3 yr olds this winter. DH had various objections to this for our DD. He pointed out none of the 3 of us had had flu previously so we didn't need vaccinating (I pointed out that this was nonsense and not having had it before had nothing to do with how likely we are to get it this year). I also pointed out that I hadn't had flu, because I get vaccinated at work every year. Is it likely that she has acquired some immunity from that? She still breastfeeds at bedtime at age 2, and I don't imagine she will have stopped by later in the autumn when I get jabbed again.