Health authorities and political aficionados began promoting the idea of mixing different COVID-19 vaccine brands as safe and effective in the spring of 2021. But was it really?
The narrative at the time was that getting the first available vaccine, regardless of the brand, provided added protection against emerging variants.
The endorsement of vaccine interchangeability was widespread, with figures like conflict of interest riddled epidemiologist Isaac Bogoch and Canada's Chief Public Health Officer Theresa Tam supporting the idea.
The U.S. Centers for Disease Control and Prevention’s (CDC) former director also endorsed mixing and matching for booster doses after a mere 10-months of observing the real-time injection roll out.
While these recommendations were being made, there was a lack of concrete scientific evidence to support the interchangeability of COVID-19 mRNA vaccines and the subsequent endorsement by health overlords.
Canada initiated a study to investigate the safety and effectiveness of mixing vaccine doses called MOSAIC. Funded with $4.8 million from taxpayers, the study aimed to assess the use of two different COVID-19 vaccines for first and second doses. The study was later expanded to include second and third doses to determine safety and immunogenicity.
The concerning aspect of the MOSAIC study is its design. It only compares vaccines against each other and lacks a true saline placebo control group. Furthermore, the study is ongoing, with the primary competition date estimated to conclude in October 2023 and full study completion in March 2024. When that data will be made publicly availability is unknown.
RNA expert Alexandra Henrion-Caude, a former research director at the French Institute of Health, expressed concerns about the genomic integration of mixed and matched vaccines at a recent expert hearing.
Dr. Henrion-Caude says that receiving Pfizer and/or Moderna (the mRNA platform) and an adenoviral based COVID-vaccine may further enable cellular integration from the foreign DNA discovered within the novel vials.
“This is a big concern of gene editing our hematopoietic stem cells,” she explains while leading into the cancer promoting potential of these safety worries.
The pharmaceutical manufacturers themselves confirmed the unknowns with interchangeability in their product package inserts.
Moderna's Spikevax and AstraZeneca's Vaxzevria both acknowledged the absence of interaction studies and data supporting the interchangeability of their vaccines with others.
While the promotion of mixing COVID-19 vaccines was widespread, the scientific evidence supporting this practice remains limited.
Studies like MOSAIC were initiated to address this gap, but it’s design and timeline raise questions about the reliability of purported experts to assert safety and efficacy, highlighting that public health recommendations continually lack a solid evidence base.