The Privileges and Immunities Clause discusses the right to interstate travel.
And the Supreme Court has confirmed freedom of movement as a Constitutional right.
However, authoritarians eager to destroy the United States don't believe citizens should have this Constitutional right.
They consider your rights as 'privileges' and think your vaccination status should determine your ability to travel.
Former Planned Parenthood President Leana Wen is one tyrannical control freak who doesn't believe in your fundamental rights.