NIH Begins Testing Mixed COVID-19 Vaccine Schedules
The U.S. National Institutes of Health (NIH) has announced that it has begun an early stage Phase 1/2 clinical trial to examining what happens when an adult who is fully vaccinated with one type of COVID-19 vaccine, is given a different booster vaccine from another manufacturer three to four months later.1
Currently, there are three COVID-19 vaccines being distributed under the U.S. Food and Drug Administration’s (FDA) emergency use authorization (EUA) status: Pfizer/BioNTech COVID-19 vaccine, Moderna COVID-19 vaccine and Janssen COVID-19 vaccine.2 The COVID vaccines manufactured by Pfizer/BioNTech and Moderna’s COVID-19 currently require two doses given three to four weeks apart, while Janssen vaccine requires one dose.3
Vaccine Makers and Scientists Say People Will Need Booster COVID-19 Vaccines
The clinical trial comes after vaccine manufacturers and public health officials have said that fully vaccinated people will eventually need a booster dose of COVID-19 vaccine because artificial vaccine acquired immunity will likely wane over time.4 5 Some have speculated that the COVID-19 vaccine may become an annually recommended vaccine similar to the annual influenza vaccination.6
Anthony Fauci, MD, director of the National Institutes of Allergy and Infectious Diseases (NIAID) said:
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.7
150 Volunteers Enrolled in the Clinical Trial
The purpose of the clinical trial is to examine the immune responses of administering a different COVID-19 booster vaccine than the one originally administered to trial participants.8 Dr. Fauci added…
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.9
Currently, there are 150 volunteers registered in the clinical trial, who have received either one of the three EUA COVID-19 vaccines. Each vaccine group will have enrolled some 25 people between the ages of 18 and 55 and about 25 people in the 56 years and older age group.10
The participants will receive a single booster dose of the Moderna vaccine twelve to twenty weeks following vaccination. They will be monitored for a period of one year after the administration of the booster vaccine to evaluate immune responses against current and emerging variants of the SARS-CoV-2 virus.11
People who have not yet received an EUA COVID-19 vaccine are also eligible to enroll in the trial in a separate cohort. These participants will receive the two-dose Moderna COVID-19 vaccine and will be assigned to receive a booster dose of a vaccine about 12 to 20 weeks later. NIH officials said initial findings should be available at the end of summer 2021.12
Canada Recommends “Mixing and Matching” COVID-19 Vaccines
Canada’s National Advisory Committee on Immunization (NACI) updated its guidance recommending the mixing and matching of second doses of COVID-19 vaccines. NACI is now advising Canadians to combine either the AstraZeneca/Oxford University, Pfizer/BioNTech or Moderna/NIAID vaccines interchangeably.13
For Canadians who have had a first dose of Pfizer/BioNTech or Moderna COVID-19 vaccine, NACI recommends they can now take either of the two vaccines as a second dose because they both use mRNA technology.14 The recommendations also state that first dose of the AstraZeneca COVID-19 vaccine can be followed by a dose of either Pfizer/BioNTech or Moderna COVID-19 vaccines.15
The updated NACI recommendations state:
No data currently exist on the interchangeability of COVID-19 mRNA vaccines… At this time, there is no reason to believe that mRNA vaccine series completion with a different authorized mRNA vaccine product would result in any additional safety issues or deficiency in protection.16
Theresa Tam, MD, Canada’s Chief Public Health Officer said that, while there is no data to support the recommendations, there are “ongoing” studies to test the effectiveness of the approach that have yet to be published.17
She said:
This is not a new concept, so having a multi-dose series in terms of vaccines given by manufacturers is something that public health have used over time for many other vaccines. When vaccine programs and supplies change this is not an unusual thing to do.18
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