Now that more vaccine options are now available, the CDC is warning people to NOT mix and match vaccines.

Health experts say Johnson & Johnson's shot should not replace a second dose from Moderna or Pfizer.

The vaccines are not interchangeable, and the effectiveness of mixing them has not been studied, according to the CDC.

The CDC says if there are delays with the Pfizer or Moderna shot, the second dose can be given up to six weeks later.