No, they would be given a deferral. In other words, they would tell the court that they will not be back from vacation until, say, Aug 12th. Then the court would defer them being called until after that time.
I was a Reservist. When 9-1-1 went down I got recalled to Active Duty. I had a friend pick up my mail for the 1st month and hold it for me until I knew where I would be for the duration, then he sent it all at once. At the same time I sent in a Change of Address to my home post office. Several months later, I received a notice to appear in federal court in a city about 50 miles from my home.
I called the court on the phone and told them I would not be able to make it because I was out of the country at the moment. The gal on the other end asked, "And when do you plan on being back?" A said, "I don't know exactly, at the earliest it will be next September." She then said, " Being out of the country does not excuse you from jury duty. You will have to find a way to return for the voir dire. And how can you be out of the country but not know when you will return?" I replied, "Because when Uncle Sam issued my travel orders, he explicitly told me that I would be gone for 1 year, with the possibility of a 12-month extension."
There was this real long silence on the other end, and finally I think I heard the sound of a lightbulb flickering on, "Are you in the military and currently overseas?" "Yes." "Then I believe you are qualified for a deferral." "I said, "That's a good thing. Because I wouldn't be there anyway." Never heard anything more about it. And never got another summons.