From unclassified military news reports, "a lot". The military is quite concerned about it and is taking a lot of preventative steps.
That's one/tenth of 1 percent. The percentage of the general population is .2 percent. That's double.
As far as the USS Roosevelt is concerned, that brings up an interesting question. Why didn't ALL military ships and bases see such an outbreak?
If you take the Roosevelt out of the equation, the infection rate would be even lower.
So, ipso facto, the flu shot did not make them more vulnerable.