𝐋𝐞𝐭’𝐬 𝐜𝐨𝐦𝐩𝐚𝐫𝐞 𝐭𝐡𝐞 𝐏𝐟𝐢𝐳𝐞𝐫 𝐚𝐧𝐝 𝐌𝐨𝐝𝐞𝐫𝐧𝐚 𝐯𝐚𝐜𝐜𝐢𝐧𝐞

I anticipate hearing about the FDA’s final EUA decision about Moderna today. If approved for EUA, that would be the second COVID-19 vaccine (behind Pfizer last week) to roll-out. Let’s compare them:


1. Both are highly effective – between 94-95%

2. Both are mRNA vaccines

3. Neither will change your body’s DNA or contain a live virus (won’t make you sick with COVID-19)

4. Neither contains a microchip, 5G, or pixie-dust =) 5. Side effects were very similar, mild, and similar to other vaccines on the market: pain at injection site, fatigue, mild fever


1. Age recommendations – Pfizer’s vaccine was granted EUA for 16+; Moderna’s vaccine (if approved) is for 18+

2. Storage – Pfizer’s has to be stored below North Pole temps (Happy Holidays, everyone) at -112 to -76 degrees Fahrenheit; Moderna’s vaccine does not require as cold of temperatures (-13 to -5 degrees Fahrenheit).

3. Vaccine stability – We know that mRNA is unstable at room temperatures, which is why we need the super-cold temps for storage (and a fat bubble – see #4). Once taken out of the fridge, the Pfizer vaccine is stable for about 5 days and Moderna is about 30 days.

4. Lipid nanoparticles – Think of these as little fat bubbles that help encase the mRNA and keep it from degrading. They are a bit different between the vaccines, and Moderna’s looks to be more stable. This is also thought to be the reason why Moderna’s trial did not have any severe allergic reactions.

5. Severe allergic reactions (anaphylaxis): These were RARE in Pfizer’s trial and none reported in Moderna’s.


1. Do the vaccines prevent transmission? We know from the data that both vaccines prevent symptomatic disease. What we do not know yet is if you can still be infected BUT you do not have symptoms. This is still good because that means you don’t get really sick with crazy symptoms that can land you in the hospital or last a long time like we see in long-haulers. But, this also means you need to still wear a mask if you get a vaccine until we know more.

2. Do the vaccines last longer than natural immunity? We think this is a strong yes (see my post from yesterday).

3. What about certain populations (pregnancy, children, etc)? This data is being collected and worked on. But, it will be a while before we have data from these studies to hear recommendations. For now, keep wearing your masks, distancing, washing hands, etc – even after the vaccine!

I’ll update this post if final EUA approval is granted for Moderna on any differences in recommendations, ingredients, or guidelines. I’ll also update with the final factsheets for healthcare providers (this contains detailed recommendations for sub-groups with certain conditions) and us in the general population. Then you can have all of that info in one-stop-shop. I also want to link to this great, short video explaining the differences (the picture is a screenshot of the video).


-Friendly neighbor epidemiologist

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