Full dose booster?

February 8, 2022 1:18 AM

Is there any danger in my taking a full 100 mcg dose of Moderna as a booster even though the boosters are typically 50 mcg? I was double vaccinated with Pfizer in the US (last dose in June 2021). I'm now in a country with limited vaccine availability, and the booster size dose doesn't seem to be available.
posted by matkline to Health & Fitness (14 answers total)

Response by poster: And, to follow up, is it possible to tell the person administering the shot that I just want a half dose?
posted by matkline at 1:41 AM on February 8, 2022 [1 favorite]

Anecdotally, my brother got three full doses and was fine (other than he still got the rona and was sick as a dog from that).
posted by joycehealy at 4:18 AM on February 8, 2022 [2 favorites]

IANYD but I don't believe there is any medical reason that receiving a full dose instead of a booster would be harmful. Anecdotally, I have several physician friends who did exactly what you are considering (full dose of Moderna after 2 doses of Pfizer) because boosters weren't yet available and they were being exposed to COVID every day at work. No one had any ill effects.
posted by purplemonkie at 5:35 AM on February 8, 2022 [1 favorite]

I got JNJ last spring and did a two-round dose of Moderna in November/December. (Relatively healthy forty something with regular exposure to college students.)
posted by noloveforned at 5:37 AM on February 8, 2022

I did what you are doing (full third dose) and the third shot left me slightly feverish, tired, and achy for six days, so prepare yourself for that possibility.
posted by eleslie at 6:38 AM on February 8, 2022

Tangential, but the Pfizer booster is the same dosage as the original Pfizer series. So there is (massive) precedent for an mRNA booster at the same dosage as the primary two-shot series.
posted by heatherlogan at 7:46 AM on February 8, 2022 [1 favorite]

I also had three full Moderna doses. I had a much stronger reaction (felt moderately sick with fever, chills, aches, tiredness) for two days after the third shot but otherwise no ill effects. So yes, plan for the side effects but I am not aware that there is any danger to a third full shot.
posted by Preserver at 8:38 AM on February 8, 2022 [2 favorites]

I also got three full Moderna doses in August, and the third one packed a much stronger reaction. Since there no fourth doses in the US, I'm wondering what's next for me.
posted by answergrape at 10:46 AM on February 8, 2022

I'm severely immune compromised and have had 4 full doses. The day after is miserable. Other than that it's been fine.
posted by jeszac at 10:54 AM on February 8, 2022 [1 favorite]

I'm also seriously immune compromised and have had four full doses of Pfizer. The third dose really knocked me out, but didn't feel anything after my fourth shot at all.
posted by twelve cent archie at 11:25 AM on February 8, 2022

I was double vaccinated Pfizer and got Moderna as a booster. The nurse explained that it would be a full dose. I was fine with it (the more vaccines the better!). I can't recall exactly what she said, something about since I hadn't gotten Moderna before that a full dose was better.

It was a bit rough for about 48 hours (body aches, fatigue) but I was able to work (from home) through it.
posted by mephisjo at 6:56 PM on February 8, 2022

My impression is that all the vaccines come in vials, and are filled in syringes per person. I don't think there is anything stopping the person drawing the dose from taking half the normal quantity. That's what happened with our Pfizer boosters, each person was asked whether they were there for a regular or booster and the syringe filled appropriately.
posted by wnissen at 7:00 PM on February 8, 2022

I give vaccines in a local pharmacy in the US. For the Moderna booster we give a full dose if this is the 3rd shot for a person who is immunocompromised, but a half dose for a typical 3rd dose booster, so there is leeway for individual circomstances. The syringes are not prefilled, and I decide whether to give 0.25 ml or 0.5 ml dose. The vials are multidose, and each syringe has to be individually filled.

Can you talk to the person who administers your booster and discuss which category you might fit in? It has gotten much more complicated as we consider J&J and the mRNA vaccines. And I have no idea about what happens after Astra Zeneca, though I've boosted a few who got the Chinese vaccine. In their case I think the patients went with Pfizer, which has boosters at the same dose as the first two, so much less confusion.

If your health professional insists on giving a full Moderna dose I think the downside would be in more side effects rather than less protection.
posted by citygirl at 8:29 PM on February 8, 2022 [1 favorite]

My impression is that all the vaccines come in vials, and are filled in syringes per person.


That might vary by local circumstances. When I got my full dose, the tech had to go get it from somewhere else as all their syringes had been pre-filled with the booster dose. But that was in a somewhat busy popup vaccination clinic.
posted by Preserver at 6:29 AM on February 9, 2022 [2 favorites]