The National Institutes of Health said Tuesday it plans to test booster shots from different vaccines in a fully vaccinated population as part of a "mix-and-match" clinical trial. The Phase 1/2 study is being funded by the National Institute of Allergy and Infectious Diseases. It will enroll 150 participants who have received either the two-dose, mRNA-based shots developed by Pfizer Inc. /zigman2/quotes/202877789/composite PFE -0.63% /BioNTech SE [b: bntx] and Moderna Inc. /zigman2/quotes/205619834/composite MRNA +2.53% or Johnson & Johnson's /zigman2/quotes/201724570/composite JNJ +0.44% single shot. The participants will then receive a booster shot of Moderna's vaccine 12 to 20 weeks after finishing their initial vaccine regimen. "We need to prepare for the possibility of needing booster shots to counter waning immunity and to keep pace with an evolving virus," NIAID Director Dr. Anthony Fauci said in a news release. Both Pfizer and Moderna are already running their own clinical trials for different types of booster shots.