Your Field Guide to the Four Potential U.S. COVID-19 Vaccines

Your Field Guide to the Four Potential U.S. COVID-19 Vaccines
Photo: M-Foto, Shutterstock

It’s been a busy month for coronavirus vaccine news. In the past few weeks, we’ve seen announcements of interim phase 3 trial results, final phase 3 trial results, an FDA application, and phase 2 results. By my count, that’s five news events about three vaccines. It’s a bit confusing.

Currently, four U.S. vaccine candidates are being tested in trials that will allow them to apply for FDA approval. (A fifth, Novovax, plans to start U.S. trials soon.) The New York Times vaccine tracker currently counts 13 vaccines in phase 3 trials worldwide. (Phase 3 is the last and largest round of testing before a vaccine is approved.)

The four vaccines being tested in the U.S. are all a bit different from one another. Some require ultra cold storage. Some require two doses instead of one. Some are mRNA vaccines, a new technology. Here’s a rundown of which is which and how they each work.


Type of vaccine: mRNA

Status: This is the vaccine that is closest to receiving FDA approval. The companies engineering it released final results from their phase 3 trial this week showing 95% efficacy, although the full data from the trials has not been released to the public. The companies applied to the FDA today for an emergency use authorization. FDA advisors will meet Dec. 8-10 to make that determination, after they have reviewed the trial data.

Storage: This vaccine requires ultra-cold storage, colder than typical freezers are able to provide.

Required doses: two.


Type of vaccine: mRNA

Status: Still in phase 3 trials. Interim results showed 94.5% efficacy, the company says.

Storage: Can stay at freezer temperature for six months and refrigerator temperature for one month.

Required doses: two.

Fun fact: Dolly Parton contributed to a research fund that was involved in the vaccine’s development.


Type of vaccine: based on a chimpanzee cold virus that cannot reproduce in humans and has been modified to carry a protein from the coronavirus.

Status: The company recently published interim results from a combined phase 2 and 3 trial. The trial had originally been planned to end in September, but was paused after one participant experienced a serious medical problem and another died. An investigation determined that those events were not related to the vaccine, and the trials were able to resume.

Storage: standard freezer temperature.

Required doses: two.

Johnson & Johnson

Type of vaccine: based on a human cold virus that has been modified not to replicate and to carry a protein from the coronavirus.

Status: This one is also in phase 3. Trials have recently resumed following a brief pause due to a participant’s illness.

Storage: standard refrigerator temperature.

Required doses: one, although the company is also testing a two-dose regimen.

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