I actually have a problem with that question on the form as well but for a different reason. Why does the child's gender even matter in the first place? I've never understood why so many government and other forms seem to need your age, race, religion, sexual orientation, gender, political party, marital status, household income, etc. Personally, I don't even think you should have to give out your first and last name in many circumstances either.
At the same time society claims to be practicing "non-discrimination" it is actually causing discrimination by further dividing people into separate groups. If you want non-discrimination, stop asking people to answer these stupid questions. Unless a particular question is vitally necessary to a form (i.e. your gender has a medical effect on something), they should leave it off. To me all of these questions are a way of treating people less like citizens and more like subjects. After all, you are no longer a PERSON but instead of a conglomeration of a certain race, gender, etc. That is complete crap and is quite dehumanizing.
As to an H1N1 vaccine, the only thing that should be on the form is the child's legal name and a blank line for the parent's signature. End of story.