From https://www.secretservice.gov

https://www.secretservice.gov/protection/#who

Who gets secret service protection:

The President of the United States
The Vice President of the United States
The President’s and Vice President’s immediate families
Former Presidents, their spouses and their minor children under the age of 16
Foreign heads of state and their spouses visiting the United States
Major presidential and vice presidential candidates and their spouses
Events designated as National Special Security Events by the Secretary, U.S. Department of Homeland Security
The President of the United States
The Vice President of the United States
The President’s and Vice President’s immediate families
Former Presidents, their spouses and their minor children under the age of 16
Foreign heads of state and their spouses visiting the United States
Major presidential and vice presidential candidates and their spouses
Events designated as National Special Security Events by the Secretary, U.S. Department of Homeland Security