Those circumstances are provided for in the 25th Amendment to the Constitution, which was passed in 1967. Section 2 states:
"Whenever there is a vacancy in the office of the Vice President, the President shall nominate a Vice President who shall take office upon confirmation by a majority vote of both Houses of Congress."
Speaker of the House is next in line.
https://people.howstuffworks.com/us-vice-presidential-vacancy-is-filled.htm
Those circumstances are provided for in the 25th Amendment to the Constitution, which was passed in 1967. Section 2 states:
"Whenever there is a vacancy in the office of the Vice President, the President shall nominate a Vice President who shall take office upon confirmation by a majority vote of both Houses of Congress."