Which vaccine is best?


A: The one you can get today.

Dylan from Northport, NY asked about the differences between the mRNA vaccines and the viral vector vaccines. Do we have a choice about which vaccine technology we get? Are there any reasons why one would be preferred over the other?

Other questions are coming in fast and furious about whether it makes sense to shop around or wait for your preferred vaccine. Some portals for finding and scheduling vaccine appointments even let you filter clinics by which vaccine is being offered. Am I supposed to choose?

🏆 These vaccines are all winners in our book! Are we saying the vaccines are identical? No. Might some people prefer one over the others for specific reasons? Sure. But all three vaccines now in use in the US (plus the Oxford-AstraZeneca vaccine in widespread use elsewhere) are effective, safe vaccines that will significantly reduce your chances of getting severe COVID-19 disease.

Let’s look more closely at some of the ways we can compare the vaccines:

Vaccine type: Pfizer and Moderna are mRNA vaccines, while Johnson & Johnson and Oxford-AstraZeneca are viral vector vaccine. Is one of those “better”? Nope. They’re different. (See links below to our favorite explainers on how each vaccine type works).

Ingredients: Yes, the vaccines have different ingredients. See links below to our posts that go into detail about what is (and is *not*) in each vaccine. Some concerns were raised about whether observant Catholics could take the Johnson & Johnson vaccine, which is developed using a process that relies on cell lines derived (decades ago) from tissue from an aborted fetus. Those cells are not an ingredient in the vaccine, and the official word from the Vatican is that “all clinically recommended vaccinations can be used with a clear conscience.” (Link below.)

Safety and efficacy: You can’t swing a jump rope without hitting a new table or chart on social media comparing the vaccines. Some comparison charts show the vaccines as being “100%” effective against severe disease, hospitalization, and/or death. There’s also been lots of push back about how that’s not a correct interpretation of the Phase 3 trial results, given technical reasons related to trial design, endpoints, post-hoc analyses, etc. We’ve linked to a couple of those debates below, but we’ll repeat the bottom line here: All the vaccines approved for emergency use have excellent safety records and are highly effective at reducing severe COVID-19.

Storage and delivery: The vaccines vary in terms of how cold they need to be kept, how long they can remain at room temp before administering, and how many doses you need. These differences have implications for how vaccination programs deploy the different vaccines for different populations. For example, the Johnson & Johnson and Oxford-AstraZeneca vaccines don’t require the same freezer infrastructure that Pfizer does, which make them good candidates for use in rural areas or on a mobile clinic. Johnson & Johnson’s 1-dose regimen is also appealing for people who really don’t like needles, or for populations where it might be hard to ensure second-dose follow-up, such as people who are experiencing homelessness.

We’ll end this post where we began: We are very enthusiastic about all of these vaccines! While you might have preferences for one or the other, we hope that doesn’t slow you down in getting your shot as soon as you can.

If you get offered an appointment and you don’t know which vaccine it will be, have confidence that all of them do what we need them to do: dramatically reduce the risk that you will get severe COVID-19 disease if exposed. Stay safe!

🧡 Love,
Those Nerdy Girls


mRNA explainer

Viral vector explainer

What’s in the Pfizer & Moderna vaccines?

What’s in the Oxford-AstraZeneca vaccine?

What’s in the J&J vaccine?

Vatican statement

Atlantic article about vaccine comparisons

Ashish Jha interview on NPR

Link to original FB post