They have different ways of working and even have different refrigeration requirements.
The AstraZeneca and J&J vaccines are viral-vector vaccines, while Moderna and Pfizer’s candidates are messenger RNA vaccines. An mRNA vaccine has never been approved by the Food and Drug Administration, while there is only one approved viral-vector vaccine, Merck & Co. Inc.’s MRK, -0.26% Ebola vaccine, which received FDA approval in December of last year.
Johnson & Johnson’s investigational COVID-19 vaccine entered Phase 3 clinical trials this week, making it the fourth vaccine candidate in the U.S. to do so and providing additional details that can help investors differentiate the pool of late-stage coronavirus vaccines.
J&J’s vaccine candidate joins a group of late-stage vaccines being developed by AstraZeneca AZN, +2.47% AZN, 0.22% and the University of Oxford, BioNTech BNTX, +6.14% and Pfizer Inc. PFE, +0.81%, and Moderna Inc. MRNA, +6.59% At least three other vaccines developed by Inovio Pharmaceuticals Inc. INO, +10.21%, Novavax Inc. NVAX, +10.85%, and Sanofi SNY, -0.02% SAN, 1.32% are also being tested in early- and mid-stage clinical trials in the U.S.
https://www.marketwatch.com/story/there-are-four-coronavirus-vaccines-in-late-stage-studies-heres-how-they-differ-2020-09-25
