I'm confused. Where does this say the vaccine is mRNA? The Valneva VLA15 website explicitly states "VLA15 is a multivalent recombinant protein vaccine" [1], and the linked press release calls it a "investigational multivalent protein subunit vaccine". Does nobody actually read these things?
It's not just the OP. I've heard from multiple sources that "Pfizer has an mRNA vaccine for Lyme in clinical trials." Somewhere along the line someone(s) saw Pfizer, vaccine, and put 1 and 1 together and got 3. And it spread. This is the first time I realized that's not true.
I've heard it described as such but, no, it seems to be a distinct if perhaps somewhat related type of vaccine? (UPDATED: It's not.) The company that actually created the vaccine is also unrelated to the company that developed the vaccine that Pfizer is currently distributing for COVID.
See [2], "Subunit Vaccines".
[1] https://valneva.com/research-development/lyme-disease/
[2] https://www.niaid.nih.gov/research/vaccine-types