I am about to go on safaris in South Africa and Zambia and need to be vaccinated against a few diseases.

The IRS publication 502 doesn't mention vaccinations explicitly, but does state that

Medical care expenses must be primarily to alleviate or prevent a physical or mental defect or illness.

So I'm assuming that is a "yes", however I'd like to know if anyone knows for sure or has already used an HSA for that purpose. Thanks.