evidence: Why mRNA vaccines aren’t gene therapies We bust another Covid-19 myth – this time about how mRNA vaccines work – in our latest blog post As people in the UK continue to receive Covid-19 vaccines, the subject of how and why they work is being widely discussed online. Some people are promoting the idea that RNA-based vaccines – including the UK-approved Pfizer-BioNTech and Moderna vaccines – are a form of gene therapy, but this isn’t accurate.