Animal models paved the way for Phase III testing of the COVID-19 vaccine

Yesterday, NIH and Moderna announced the start of a multi-site, Phase 3 clinical trial of a candidate vaccine for COVID-19. This candidate vaccine uses messenger RNA, or mRNA, a “codebook” that cellular machinery “reads” in order to build proteins. For this candidate vaccine, the mRNA contains instructions for building spike proteins found on the coronavirus, which help the virus enter human cells. 

We know from foundational studies in animal models, particularly mice, that the vaccine induces cells to make the spike protein, which then prompts the immune system to make antibodies that attach to the spike proteins. The working hypothesis is that these antibodies may prevent the virus from infecting healthy cells. Indeed, Science News reported in February that

“Mice vaccinated with these mRNAs were protected against lung infection when researchers later exposed the rodents to SARS-CoV-2, the coronavirus that causes COVID-19” 

Source: The Jackson Laboratory

Subsequently, earlier this month, researchers published a preliminary report on the successful Phase 1 clinical trial of the vaccine, dubbed mRNA-1273. The vaccine quickly moved to Phase II trials, although the results are not published yet (you can follow the progress of COVID-19 vaccines with the New York Times Coronavirus Vaccine Tracker, which importantly also highlights preclinical tests — those done in animals). 

Animal research did not contribute just to the preclinical stages of testing the vaccine for safety and efficacy. Mammalian cells, derived from animals like mice and rabbits (among others), are used to produce the vaccine (see how vaccines are made in our post here). 

While it will still be many months before we know how successful this candidate vaccine is, it’s clear we wouldn’t be this far along without the critical contributions of responsible animal research.