NIH Starts Trial Assessing 'Mix & Match' COVID-19 Vaccine Approach

There is a new clinical trial underway to assess the safety and effectiveness of mixing different types of booster shots in adults who have been fully vaccinated against COVID-19.

"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 to keep pace with an evolving virus," said Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases (NIAID), which is part of the U.S. National Institutes of Health (NIH). NIAID is leading the trial. "The results of this trial are intended to inform public health policy decisions on the potential use of mixed vaccine schedules should booster doses be indicated," Fauci added in an NIH news release.

The trial will include about 150 people who have already received one of three COVID-19 vaccines approved for use in the United States -- Johnson & Johnson, Moderna, or Pfizer-BioNTech. Each of three groups will include about 25 people ages 18 to 55 years old and about 25 people who are older. Twelve to 20 weeks after completing their initial vaccination regimen, participants will receive a single booster dose of the Moderna vaccine. People who have not yet received a COVID-19 vaccine are eligible to enroll in a separate trial group. Initially, they will receive the two-dose Moderna vaccine and then get a booster dose of a vaccine about 12 to 20 weeks later.

The volunteers will be followed for one year after their booster shot. They will be asked to complete telephone check-ins and in-person follow-up visits, and to provide periodic blood samples to help researchers evaluate immune responses against current and emerging variants of severe acute respiratory syndrome coronavirus 2. If participants develop confirmed COVID-19 with symptoms, their samples will be tested to determine if their infection was caused by a variant strain of the virus.

Initial findings are expected in late summer 2021, according to the NIH.