I don't understand "I do not think that you necessarily need to infer that" - Why not?
Because such an inference would be incorrect.
He is saying that the reason for giving the vaccine to 12 year olds is not
due to a belief that those 12 year olds are immediately at risk.
Is such inferring harmful?
Perhaps not. If someone gave the vaccine to 12 year olds, and erroneously believed that the vaccinations were because the 12 year olds were facing an immediate risk, I do not see how this erroneous belief would cause harm.
On the other hand, if someone erroneously believed that the vaccine should only be given to people who are at immediate risk, and if they failed to vaccinate a 12 year old because they assessed that there was no immediate risk, that failure to vaccinate the child would be harmful.
I believe the idea behind vaccinating 12 year olds, even if there is no immediate risk, is because it may not be apparent to the adults when a child becomes sexually active. Better to get the vaccination done early, just to ensure that it is done before the child becomes sexually active.