"last vacation" is a correct and usable phrase in written English.
You can use it to refer to a vacation that happened in the past, such as "I had a great time on my last vacation to the Caribbean."
I think this was my last vacation, and certainly my last camping trip, so memorable in every other detail.
"I would estimate it to be about 200 pages, given what I saw in late August during our last vacation, and given what I knew of Stieg's workload in his last two months".
He took his last vacation to, well, no one can recall when he took his last vacation.
G.S. On my last vacation, I worked for NASA.
He can guess the name of your dog and where you spent your last vacation.
Loren sports an orange tan that suggests her last vacation was on Three Mile Island.
"The only vacation I plan is the last vacation," he answered.
(His last vacation was three years ago, a weekend wedding in Hawaii).
He last vacationed in Wildwood when he was 15.
For some reason that is unclear to us at the present writing, the family last vacationed in 2007, a short trip to a theme park in Orlando, Florida, at school break time, which Mr. Forbisher was heard by friends to describe as "a nightmare that will never be repeated".
Labor Day weekend is a holiday of lasts: last summer Fridays, last summer vacations, last chance to wear white shoes without committing a fashion faux pas.
