mRNA (Pfizer, Moderna) vax dose sizes

[EPguy]

I've looked deeper into mRNA dose sizes, as it has been an ongoing subject of confusion, esp in our UK cohort. To help any member seeking clear info here are some unusually clear results:

The extra simple answer is, the half dose Moderna shot *always* has a higher dose than the Pfizer vax. Of course if they change the dosings (hasn't happened so far) this could change.

If you want the largest mRNA dose and are allowed to select it, choose any Moderna over Pfizer. Not to say pfizer is not good, I got Pfizer, but I would have selected Moderna 3rd dose if I had been allowed.

The confusion is using volume of vax rather than weight of it. Weight is the correct measure.

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Here are the long details to check my findings:

I used largely UK sites for reference to keep it most relevant for UK.

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gov.uk/government/publicati...

Moderna Booster is 50mcg, regular dose is 100mcg.

<<... the booster dose (0.25 mL, 50 micrograms) ... one dose of Spikevax (Moderna's shot) (0.5 mL, 100 micrograms) ... second dose of Spikevax (0.5 mL, 100 micrograms) to complete the primary vaccination course.>>

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Some of the confusing numbers relate to the liquid volume vs active weight <<0.25 mL, containing 50 micrograms mRNA.>> It's like "how much weight of sugar is in your cup of tea" where the sugar is the drug and how full the cup is doesn't matter.

It seems that the ml (volume of liquid) gets confused with mcg, (weight of mRNA vax) A totally reasonable confusion. It's actually the weight, mcg of vax, that matters as it measures the actual amount of mRNA vax.

If there is contra evidence it is always helpful to know but all the studies I've seen use mcg to define the dose. In the link below <<The mRNA-1273.211 vaccine ... is being studied at both the 50µg (N=300) and 100µg (N=584) dose levels. >> weight in *mcg* (µg) is used to define the dose.

cancertherapyadvisor.com/ho...

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Pfizer is 30mcg for all adult doses.

<<One dose (0.3 mL) contains 30 micrograms of tozinameran, a COVID-19 mRNA Vaccine (embedded in lipid nanoparticles).>>

medicines.org.uk/emc/produc...

There may be a benefit for the larger doses, see

healthunlocked.com/mpnvoice...

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In summary it appears US and UK use the same measures, in mcg Pf= 30, Mod = 50 or 100.

[EmeraldA]

Thanks for posting ET guy!

[souplover]

Yes, but do we know, is it better for us to ask for the full dosage? Is there a downside?

[EPguy in reply to souplover]

You may want to discuss with your Dr. Broadly the Moderna shots tend to cause more side effects, the "flu like" symptoms we hear about, presumably from the larger dose. But as they say, everyone is different. I'm not aware of differences in the very rare serious effects, but as always they learn more each month.

Of course it's a lot better to get any size booster than get "vaxed" by catching Covid.

In this post, I noted the fairly direct relation between booster dose and antibody response, where antibody level has been correlated to protection.

healthunlocked.com/mpnvoice...