Mixing Moderna and Pfizer?

[Paul123456]

Does anyone know if you can have a Pfizer 3rd Primary and a Moderna booster?

I’ve had two AZ’s and a Pfizer 3rd. Thinking a Moderna booster would give optimal protection

[EPguy]

We don't have 4th dose yet in US yet. But you're likely familiar that Moderna is a higher dose than Pf at 50 vs 30mcg for the booster and data suggests it may be more effective. I would choose the booster from Moderna if I get the choice.

This post has booster results for dose sizes.

healthunlocked.com/mpnvoice...

[MWxxxx]

I think for our 4th dose we can have either pfizer or moderna. This time the moderna will be a 1/2 dose but Blood Cancer Uk say we can have either. It was just for the 3rd primary dose that we should get pfizer as it was a higher dose, for the booster apparently it doesn't matter. I will be having my booster next week but I'm not sure which one I will get. In my area there seems to be more moderna about than pfizer.

[EPguy in reply to MWxxxx]

If UK is as US, both types of adult doses of Mod are larger than the one type of Pf dose. So if you seek a larger dose, choose Moderna in either adult version available to you. See the link in my reply above.

If UK is different that will be very helpful info to know.

[MWxxxx in reply to EPguy]

I think in the UK Pfizer is 0.3 and Moderna is 0.5 but when you get Moderna as a booster it is a half dose: 0.25, which is why for the 3rd primary dose people were advised to ensure they got Pfizer. The 4th dose recommendation seems to be either Pfizer or Moderna but Moderna will still be a half dose. Sorry for itallics - I've pressed something on my keyboard and it won't go away!

[EPguy in reply to MWxxxx]

It is most confusing so I looked deeper to UK info. From this UK site for Moderna:

gov.uk/government/publicati...

<<... the booster dose (0.25 mL, 50 micrograms) ... Individuals who have received one dose of Spikevax (0.5 mL, 100 micrograms) should receive a second dose of Spikevax (0.5 mL, 100 micrograms) to complete the primary vaccination course.>>

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 Cola syrup concentrate is in your 2 liter bottle."

It seems that the ml (volume of liquid) gets confused with mcg, (weight of mRNA vax) A totally reasonable confusion. It's actually the 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 referenced link above <<The mRNA-1273.211 vaccine ... is being studied at both the 50µg (N=300) and 100µg (N=584) dose levels. >> Note mcg (µg) is used to define the dose.

In summary it appears US and UK use the same measures, in mcg Pf= 30, Mod = 50 or 100. So my note stands that for those seeking a max dose of mRNA, get Moderna in either version if allowed in your area.

[MWxxxx]

Yes, that is definitely getting confusing - especially as I'm reading this late in the evening! In the UK for the boosters we either get a pfizer full dose or a moderna 1/2 dose. We can only get a moderna full dose for 1st and 2nd vaccines and for a 3rd primary dose - not for boosters.

[EleanorPV in reply to MWxxxx]

I’m in the uk and have fought to have my 3rd dose. I can’t have the Pfizer as I had a reaction. I believe I’m getting a full dose of Moderna.

[EPguy in reply to EleanorPV]

Are you sensitive to an ingredient unique to the Pfizer shot? If not the Moderna mRNA shot is similar, just in a higher dose. On average the Moderna shots cause more reaction, usually thought to be from its higher dose. The 100mcg dose you're planning is much more than the Pfizer (3 times more)

If you are concerned about a reaction you should discuss with your Dr first. Some people select the J&J for example if mRNA is a concern.

[EleanorPV in reply to EPguy]

I had a reaction to

Something in the Pfizer shot. No available J&J is Scotland. I’m still waiting on the NHS to decide what is best for me. Fingers cross Omicron doesn’t get me first.

[EPguy in reply to EleanorPV]

Look forward to learning the NHS advice. There should be approval soon for Novavax, which has been quite good in trials and uses a different tech than Pf or Moderna. It seems to be approved already in EU. But likely not soon enough in UK (or US) for Omicron.

[EPguy in reply to MWxxxx]

Please do read it when you're ready. There is confusion when there should not be.

To say again in the simplest form: the current Moderna 1/2 dose is always larger than the current Pfizer adult dose.

[MWxxxx in reply to EPguy]

Hi. Firstly I just wanted to say that I enjoy reading your posts and the information you manage to seek out and share with us all. I always find it really interesting and informative. I cannot argue with your figures, I was just quoting the official guidance here in the UK, which was for people receiving their 3rd primary dose to ensure they got either pfizer or insist they were given a full moderna shot (lots of the vaccination centres were giving only 1/2 dose modernas as part of the booster programme which was happening at the same time). There are lots of people here in the UK who were wrongly given a 1/2 dose moderna as their 3rd primary dose when it should have been a full pfizer or a full moderna shot. Your article will certainly reassure them that they have not missed out. Likewise, I was a bit apprehensive about my booster on Tuesday as I'm not sure if I will get a full pfizer or 1/2 moderna - but after reading your article I am not so concerned. Thank you for sharing.

[EPguy in reply to MWxxxx]

Thanks for checking it out. I agree the UK official info is the problem. I don't know if it's actually wrong or just incomplete. It's frustrating to see members here who are trying to understand what their options are and don't have clear guidance to do so.

I may post this in edited form for a general post, might be helpful.

[MWxxxx in reply to EPguy]

Yes, I think that would be helpful to people. To be honest I wouldn't be a bit surprised if the UK official information is wrong. I agree that it is very frustrating that we have to try and sort it all out ourselves. It's good that we have people like yourself looking out and sharing information when you find it.

[Eadaoin]

I had my 4th jab today after AZx2 and Pfizer for third primary. Was offered a choice of Pfizer or Moderna. Chose the former. This was at a London hospital and the vax was expertly given by a charming Royal Navy helicopter pilot on secondment to the NHS. Just how lucky can a girl get?

[piggie50]

Hi Paul,I’ve had 3 Pfizer and went for my 4th on Thursday, the receptionist went off and checked and said I should have Pfizer again. I was happy with that so went with it.

Slightly sore arm on day of jab and no other side effects.

Judy