Evidence shows that by the end of 2020 there were mRNA-based COVID-19 vaccines with ~94–95% efficacy that were authorized and being deployed:

• Pfizer–BioNTech (BNT162b2): Final Phase 3 analysis reported about 95% vaccine efficacy against symptomatic COVID-19. (investors.biontech.de) The U.S. FDA then issued an Emergency Use Authorization (EUA) on December 11, 2020, making this mRNA vaccine available for use in people 16 and older in the U.S. (nasdaq.com)
• Moderna (mRNA‑1273): Phase 3 trial results published at the end of December 2020 showed 94.1% efficacy against symptomatic COVID‑19. (nih.gov) The FDA granted EUA on December 18, 2020, so this second mRNA vaccine was also available in the U.S. before year-end. (nih.gov)

Because at least one—and in fact two—mRNA vaccines with efficacy in the 90–95% range were authorized and available for use by December 31, 2020, Jason’s prediction that “by the end of the year we’d have vaccines … with 90–95% efficacy” was borne out by events.