For a short video summary of this article please see here (free account required).
When the world first heard about a new coronavirus causing severe respiratory disease in January 2020, nobody thought that less than a year later two Covid-19 vaccines would be authorized for emergency use. But mRNA vaccine technology stepped up to the challenge!
OTS highlighted the initial phase I/II results as “OTS Joint July 2020 Papers of the Month.” Now, the two papers presenting the phase III trial results that supported the emergency use authorizations have been selected as the “Joint December 2020 Papers of the Month.” These papers represent a real breakthrough for the mRNA field and more generally, for rapid vaccine development in response to emerging pathogens.
For an explanation of coronavirus mRNA vaccine safety and efficacy, please see this video:
A recap of the similarities and differences between the mRNA-1273 (Moderna) and BNT162b2 (Pfizer/BioNTech) vaccines: mRNA-1273 is given 28 days apart, at a dose of 100 μg, while BNT162b2 is given 21 days apart at a dose of 30 μg. Both are administered intramuscularly. In the trials described here, vaccine efficacy was measured as prevention of symptomatic Covid-19 at least 7 days (BNT162b2) or 14 days (mRNA-1273) after the second dose.
As has been widely discussed in the press, both the BNT162b2 and mRNA-1273 Covid-19 vaccines showed impressive efficacy: 95% and 94.1% reduction in symptomatic Covid-19 illness, respectively. Vaccine efficacy was similar across all subgroups (age, sex, race and risk for severe Covid-19) with infection rates starting to diverge 12-14 days after the first dose.
In both trials, adverse events were transient, mild to moderate and consistent with immune activation by the vaccine. Local reactions were mostly limited to injection-site pain. Systemic reactions such as fatigue, headache, muscle pain and chills were at levels comparable to approved vaccines for other diseases. There was no difference in the incidence of serious adverse events between vaccine and placebo in either trial.
Cases of anaphylaxis after receipt of mRNA vaccines have since been reported, but at 4.7 cases/million and 2.5 cases/million for BNT162b2 and mRNA-1273, respectively, these are extremely rare. The suspected cause for these reactions is the polyethylene glycol contained in the lipid nanoparticles used for delivery of the mRNAs.