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Original poster

Difference between third dose and booster

35 replies

PinkWednesdays · 31/12/2021 09:19

I’m struggling to understand the difference between a third dose and a booster. Does anyone know

Google tells me a third dose is just that, another dose, whereas a booster is intended to boost the previous doses. That makes sense but what does it actually mean?

Is a booster a smaller dose, or is there something else in the booster?

I’m just curious, as I was having this discussion with my parents who were talking about a third dose and a booster interchangeably, and we realised we didn’t know the difference in practical terms.

OP posts:
ChessieFL · 31/12/2021 09:21

The booster is half the dose of the third dose e.g. 0.25 of the active ingredient instead of 0.5 or whatever.

LaChatte · 31/12/2021 09:22

Not sure about UK but I think here in France the 'booster' dose is the same as the 1st and 2nd jabs.

mynameiscalypso · 31/12/2021 09:23

For Pfizer at least, they're the same dose/injection. The main difference is if you have a third primary dose, you're are eligible for a booster three months later. Basically, some people need three doses to get the same level of protection as two doses give most people. It's generally because they're immune suppressed so won't have such a strong reaction to the vaccine and need a bit extra to get them up to the same level.

mynameiscalypso · 31/12/2021 09:23

@ChessieFL

The booster is half the dose of the third dose e.g. 0.25 of the active ingredient instead of 0.5 or whatever.
I think that is the case for Moderna, for Pfizer, it's exactly the same dose.
dementedpixie · 31/12/2021 09:25

@ChessieFL

The booster is half the dose of the third dose e.g. 0.25 of the active ingredient instead of 0.5 or whatever.
Only the moderna booster is a ½ dose. The pfizer/AZ are a full dose
ChessieFL · 31/12/2021 09:25

Thanks Calypso, didn’t realise it was different for the different types. My booster was Moderna and they had a poster up explaining the difference between booster and third dose.

Mindymomo · 31/12/2021 09:27

You get a third vaccine if you are one of the 500,000 people with health conditions and are immune suppressed. This will be either a full dose of Pfizer or full dose Moderna. These people will then be coffered a booster of full dose Pfizer or half dose Moderna. They will have 4 doses in total.

For the rest of the population, they get full dose of Pfizer and half dose of Moderna as booster. These will have 3 doses in total.

Original poster
PinkWednesdays · 31/12/2021 09:39

I understand all that, but if the booster is the same dose as a dose, then what is the actual difference?

OP posts:
Original poster
PinkWednesdays · 31/12/2021 09:40

For the rest of the population, they get full dose of Pfizer and half dose of Moderna as booster. These will have 3 doses in total

Absolutely everyone I know who has had a booster and I’ve spoken to has had the Pfizer, regardless of whether the first two doses were AZ or Pfizer.

OP posts:
dementedpixie · 31/12/2021 09:41

It helps boost your immune response
Its the same as childhood vaccines. The 2nd MMR is called a booster but is also the same as the 1st dose

Original poster
PinkWednesdays · 31/12/2021 09:46

Right, so it’s just the terminology. So strictly speaking, those who are immunocompromised get four doses and everyone else gets three. There is absolutely no difference in what is actually administered for a third dose or a booster?

I came across a website yesterday that said it’s key that patients know if they’re getting a third dose or a booster, as there have been cases of patients going to get a third dose but actually it’s the booster, and it is important that it’s given in the right order for it to work.

www.myeloma.org.uk/news/patients-could-be-missing-out-on-covid-19-vaccines-as-confusion-grows-over-the-third-jab-and-booster/

If it’s exactly the same, then why does it matter?

Essentially I’m concerned that my mother, who is immuno compromised, got the wrong thing!

OP posts:
Whattodoin2022 · 31/12/2021 09:49

The moderna booster is not a full vaccine dose as previously mentioned so can't be called a vaccine and probably easier to say booster for Pfizer and AZ.

dementedpixie · 31/12/2021 09:50

Moderna is a different dose although it's Pfizer that's given where I am.

Original poster
PinkWednesdays · 31/12/2021 09:52

@Whattodoin2022

The moderna booster is not a full vaccine dose as previously mentioned so can't be called a vaccine and probably easier to say booster for Pfizer and AZ.
Right, ok. That makes sense. So if you have the Pfizer, you’re given exactly the same for a booster or third dose, but if it’s the moderna, it’s half a dose for a booster.

Thank you, I’m not so concerned anymore!

OP posts:
MerryChristmas21 · 31/12/2021 09:52

Do you know what your mum has had for the three she had?

I have read that the third needs to be given before the booster because of the various combinations & strengths. But there are so many variables!

dementedpixie · 31/12/2021 09:53

Sounds like it's how the doses are recorded thats the issue rather than the vaccine itself. If its recorded as a booster rather than 3rd vaccine then that causes issues if that person is supposed to get a 4th dose

Original poster
PinkWednesdays · 31/12/2021 10:00

@MerryChristmas21

Do you know what your mum has had for the three she had?

I have read that the third needs to be given before the booster because of the various combinations & strengths. But there are so many variables!

AZ for the first two doses and Pfizer for the third, but it probably is recorded as a booster instead of a third dose because she got it at a walk in and it sounds like they didn’t ask her.

Thank you everyone, this has been helpful!

OP posts:
mynameiscalypso · 31/12/2021 10:19

If she has a letter from her consultant/treatment team saying she is eligible for a third primary dose, you can apparently just take that to a walk in centre and they'll give you a booster once three months have elapsed. I have yet to try this out so not sure if it will actually work but that's what the NHS page on Covid vaccines says...

How2Help · 31/12/2021 10:20

Vaccination aims to elicit a certain response by the immune system. More than one injection may be needed to get this response. This is called the primary course and for covid this primary course is two jabs. This is what is called priming the immune system.

You can then have boosters. These cause a different response by the immune system. It boosts the immune response and provides longer lasting protection.

So doses given in the primary course and as boosters may be the same (eg with Pfizer) but the purpose of them and the technicalities of the immune response are different.

In some people with weakened immune systems (eg taking medications which reduce the ability of the immune system like chemotherapy) they need three jabs to form the initial primary response. So their third dose is still part of their primary course.

So a third injection may be the third injection in a primary course for some people, or the first booster dose in others.

It needs to be recorded accurately as 1st, 2nd, 3rd or booster dose so that a) you can be called for next dose correctly (eg 3rd jab as a booster may be 12 weeks after second dose but a 3rd jab as a third dose for immunocompromised people may be sooner). It is also important for moderna - someone getting a 3rd jab as a booster gets a half dose, a 3rd jab as part of primary course is a full dose.

For Pfizer it practically makes little difference. Timing wise for all doses it makes little practical difference since they reduced the gap to a booster dose. It is, at this stage, more a technicality and one that immunocompromised people need to be more aware of for various reasons due to how badly the recording of it has been managed.

wonkylegs · 31/12/2021 10:25

@PinkWednesdays in her case (that combination) it will be a recording thing rather than an actual difference with the meds.
If she has a letter saying she was eligible for the 3 jabs and a booster then she may need to take this when she books/attends the 4th session. She may also need to keep track of when that is due because the recall has been a bit patchy.
I'm in the exact same situation (immunosuppressed) , my vaccine record doesn't record them as boosters or other it just gives the batch number, date and manufacturer for each one.

How2Help · 31/12/2021 10:26

What is the nature of your Mum’s immunocompromisation? Has she specifically been told she needed a third primary dose? It is not all immunocompromised people - only the most severely affected. If she is one of those she has had the correct course so far as she had Pfizer, but she may need to sort out how it is recorded on the system to make sure she gets her booster dose (4th injection).

Cookerhood · 31/12/2021 10:27

For the vast majority of people who need 4 doses the third will have been recorded as a booster rather than a third dose as the recording system had no way of distinguishing between the two. I think this has now been fixed as there's a question about whether the person is immunosppressed. Anyone who needs the booster after a third dose should take their letter from their consultant. The only important distinction is if people are having Moderna - the first, second & third dose should be 0.5mL (ie full dose) and the booster, whether it is the 3rd or 4th vaccination should be a half dose (0.25 mL). Pfizer is the same for all.

RevolvingPivot · 31/12/2021 10:32

Please contact your Doctors Practice to bookin your 3rd covid booster jab

I thought the 4th jab was the booster. I received the above text.

RevolvingPivot · 31/12/2021 10:33

I meant to put 3rd not 4th

LadyLazarus40 · 31/12/2021 10:37

@PinkWednesdays

I understand all that, but if the booster is the same dose as a dose, then what is the actual difference?
Nothing but those who are given a 3rd dose will also go on to have a booster so 4 doses in total.
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