On Jun. 16, 2021, Kaiser Permanente Washington Health Research Institute (KPWHRI) announced that was recruiting volunteers in the Seattle area for a national clinical trial funded by the National Institutes of Health (NIH) exploring the possible benefits of pairing doses from different COVID-19 vaccines.

In the new study, KPWHRI and 8 other research centers in the Infectious Diseases Clinical Research Consortium assessed the use of different boosters that may or may not match the type of vaccine that participants received earlier. The researchers aim to determine the safety and effects of mix-and-match boosters on immunity to SARS-CoV-2, the coronavirus that causes COVID-19.