The National Institutes of Health (NIH) announced Tuesday that it has started a clinical trial of adults fully vaccinated against COVID-19 receiving a different booster shot approximately three to four months later. The study will determine the safety and immunogenicity of mixed booster regimens against COVID-19, the disease caused by the CCP (Chinese Communist Party) virus, and emerging variants. Some 150 adults who have received one of the three COVID-19 vaccines currently available under the Food and Drug Administration’s (FDA) emergency use authorization in the United States will take part in the trial, the NIH said. The three COVID-19 vaccines currently available in the United States so far are the Johnson & Johnson, Moderna, and the Pfizer-BioNTech. “Although the vaccines currently authorized by the U.S. Food and Drug Administration offer strong protection against COVID-19, we need to prepare for the possibility of needing booster shots to counter waning immunity and …