WASHINGTON, (Reuters) – Americans have the option to get a COVID-19 boost shot. However, the White House chief medical advisor Dr. Anthony Fauci stated that they should stick with their first inoculation.

Fauci, who is also the Director of the National Institute of Allergy and Infectious Diseases stated in an interview that “it’s generally recommended that the booster that was the original regimen you received in the first place” in a CNN interview.

Fauci told CNN that “but for one reason or another” – which can be due to different situations, availability, or simply different personal preferences – it is possible to mix and match.

Thursday’s recommendation by the U.S. Centers for Disease Control and Prevention was to recommend the COVID-19 vaccination boosters for those who have received the COVID-19 vaccine. Moderna (NASDAQ:) Inc and Johnson & Johnson (NYSE:) shots, and said Americans can choose a different shot from their original inoculation as a booster.

Fauci’s statements were contrary to those made by the CDC and Food and Drug Administration last week. These recommendations suggested that Americans receive boosters. However, they did not give specific suggestions on which combination would work best.

The recommendations also opened the door for recipients of the one-shot J&J vaccine to get a dose of the Pfizer Moderna or NYSE: vaccines have shown greater protection through a range of research.

Fauci stated that you can mix and match, but it is best to stick with your old regimen.

While these vaccines have proved to be very effective in protecting against serious illnesses and deaths, scientists at the Government have recommended that boosters should also be used, particularly since the highly contagious Delta variant could cause breakthrough infections even among fully-vaccinated people.