Covid-19 vaccines and vaccinations

~90% effective in whom?

Efficacy figures that aren't based on randomised clinical trials and where there are significant differences in demographics aren't comparable (for example claims that the AZ vaccine has over 70%+ efficacy against symptomatic disease, when those subgroups where that was found were younger/healthier). Also note the short-term followups. In the long term, there is a tendency for regression to the mean and I'd expect lower figures simply for that reason.

The raw figures in the study you linked was 75% in the second week, but note that this was in healthy health-care workers. The efficacy in the elderly and the most vulnerable is always lower. So while the overall efficacy (against symptomatic disease) for two doses versus one may look like it is only a few higher percent overall, the gap is likely to be significantly higher in the most vulnerable. We won't really ever know for sure exactly how much difference as there will never be larger randomised trials.

 

Vaccine dosing and spacing (video includes David Strain):

https://www.youtube.com/watch?v=x5R5hZ5do3M

This appears to be the data they are discussing:

https://assets.publishing.service.g...estimated-efficacy-of-single-vaccine-dose.pdf

 

Not sure if this link has been posted here:

https://www.gov.uk/government/publi...professionals-on-covid-19-vaccine-astrazeneca

https://www.gov.uk/government/publi...are-professionals-on-covid-19-vaccine-moderna

https://www.gov.uk/government/publi...roval-of-pfizer-biontech-vaccine-for-covid-19

 

I just want to point out that the video is not publically listed and they (MDBriefCase) claim that it is only for medical professionals. I have read the transcript and it seems none of those speaking were experts in the immunology of vaccines and they did not discuss the underlying reasons (eg germinal centre kinetics) that play a role in how well the antibodies are able to neutralise the antigen, nor the relationship between booster timing and the subsequent antibody titre (nor any understanding of long term antibody titre kinetics).

 

May have missed it, but I am wondering exactly what, say, a 90% efficacy means. Is it 90% of people have immunity but 10% don't? Or does an individual have a 90% chance of not getting sick if they meet the virus?

 

The efficacy refers to efficacy against symptomatic infection. In a large scale vaccine trial, it is impossible to really say who has really been exposed to the virus or not, so efficacy is calculated as:

Efficacy = (incidence of symptomatic infection in unvaccinated people - incidence of symptomatic infection in vaccinated people)/incidence of symptomatic infection in people

(and usually expressed as a percentage)

The incidence period can vary between different trials and longer incidence periods may give some variation in the efficacy calculations, not only based on the accumulation of exposure over time for the participants, but also potentially any subtle variations in immunity over time. There is of course an expectation over time of 'regression to the mean'.

 

Thanks, it's nice to have knowledgeable people on this forum. Sounded too good to be true I thought.

 

There have been several reports of hypersensitivity reactions to the mRNA vaccines (Pfizer and Moderna). Some people suspect one of the ingredients in the lipid layer encapsulating the mRNA called polyethylene glycol (PEG) could be implicated. These reactions are extremely rare and, if they happen, the staff are trained how to deal with it.

https://www.sciencemag.org/news/202...id-19-vaccine-trigger-rare-allergic-reactions

 

So, basically, lots of information but nothing that tells you what you want to know

I find weather forecasts to be much the same!

Thank you.

 

Yes, the form I had to fill in asked about PEG, I think.

 

I had the AZ vaccine this week due to being in Category 6. The first day I just had soreness at the injection site and a bad headache. I woke up that night with chills and then intermittent fever and the 2nd day I've had muscle weakness, fever, nausea and a really bad headache. I felt like I was too tired to do anything except rest in bed. I tried taking extra steroids (I'm steroid dependent) to see if it would help but the symptoms persisted. Paracetamol helps a bit. I'm hoping it will be better tomorrow.

Does anyone know....

1) Would having stronger "side effects" indicate that you are mounting a stronger immune response and making more antibodies or is there no correlation. My parents had the same vaccine (AZ) a few weeks ago and one had just a sore arm and the other just felt tired for a day. They think their immune systems are weaker due to being older.

2) What exactly is your immune system doing that causes you to have a headache, nausea, muscle weakness. I mean what are the biological mechanisms at work? When I look it up on the NHS website it just says you get side effects because your immune system is responding to the vaccine which is very vague. I'm curious to understand what is going on inside your body that ends up giving you those kinds of symptoms.

@Sly Saint
I was worried about having the vaccine as I've had some bad drug responses in the past (face swelled up, hives, bronchospasm) but I didn't get any kind of immediate bad reaction like that to the AZ vaccine.

 

The answer is no clear association. Antibodies aren't being produced 2 days after the inoculation. In the first few days after the first dose primarily the innate immune response contributing to the symptoms. In principle, if the innate response is too strong and effectively clears out the antigen then you will get poorer quality antibodies. The B-cells slowly improve their B-cell receptors over 2-3 weeks after forming germinal centres in the lymph and undergoing the somatic hypermutation process. Long term efficacy is more related to neutralising quality, rather than the quantity of antibodies.

I will however note that it is after the second dose that most people report symptoms, rather than the first. After the second dose, the leukocyte are now primed with circulating antibodies and this leads to rapid clonal expansion of memory B-cells. In principle, if the circulating antibodies are effective in neutralising the antigen, then far less B-cell germinal centre activity will result as there won't be enough antigen to sustain this process. If the antibodies are partly effective, then some B-cell germinal centre activity will result, but this won't necessarily be enough to improve the neutralising quality by much. (this is what leads to the 'original antigenic sin' effect)

Stimulation of the respective afferent nerves. I'd suggest this is due to cellular or viral debris. There is also suggestion that vascular damage, such as that caused by cytotoxic T cells initiating inflammatory cascades that damage nearby endothelial cells leading to greater vascular permeability and thus nerve afferent stimulation.

For fever:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4870994/
For nausea:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3893663/
For fatigue:
https://www.sciencedirect.com/science/article/abs/pii/S1566070214001738

For headaches (non-migraine), it is a big vague, but I suspect this is also vascular in nature.

 

I wonder how many people know all of the things they are allergic to or intolerant of. I've had eczema most of my life, and although I know some things which can trigger a bad episode I do get flares of the condition that I can't explain or attribute to anything.

Edit : I don't know whether polyethylene glycol is something I react to.

 

me neither, but I do react to phenoxyethanol (can be found in ultrasound gels, not severely but will produce a rash), which is also a glycol, and propylene glycol is also a well known allergen for some but I don't know how they relate to each other.

 

Just a quick update to say that I was able to get the Pfizer vaccine after turning down my first invitation for Oxford/AstraZeneca a couple of weeks ago (my GP surgery had its first delivery of Pfizer this week since the first week of January!). I was a bit worried about asking for a specific vaccine because the public health message in the UK seems to be that there is no choice and that you should take the first vaccine you are offered. However there were no issues with my GP surgery in asking - they are running separate clinics for the different vaccines and were very happy to book me in for the vaccine of my choice.

So I had my first dose of Pfizer vaccine on Thursday. I’ve never had any allergic reactions but I can be sensitive to medications so I was a little anxious beforehand. I was a bit wiped out for the following two days but that could probably be explained by the exertion of getting to the GP surgery and back. I didn’t otherwise notice any side effects apart from a very slight headache and a sore arm. Overall I’m just feeling happy and relieved to have received my first dose of vaccine.

 

That's good to know @JaneL . Sorry if you've covered this previously, but can I ask why you wanted the Pfizer rather than AZ?

I'm trying to decide whether to call my GP and request I be considered for group 6 or not. I feel like if it's going to give me a relapse there's no point in trying to get is sooner. On the other hand, if it didn't cause a relapse it would make my life a lot easier to have it now.

Do people think it's too early to be getting a general sense of how common ME relapses after the vaccine are?

 

this is from a week ago
Covid Vaccinations and ME/CFS: Community Feedback!
https://meassociation.org.uk/2021/02/covid-vaccinations-and-me-cfs-community-feedback/

 

Hi Tia. It was because the clinical trials showed that the efficacy (the percentage reduction of disease in the vaccinated group of people compared to the unvaccinated group) is considerably better for the Pfizer vaccine than for AZ.

Personally I decided that the risk of relapse would be much greater from getting covid than from the vaccine (but I don’t suffer from allergy and I’ve never had a bad reaction to a vaccine so that made the decision a lot easier)

My overwhelming impression is that severe relapses are much more common in people with ME after getting covid than after getting the vaccine (I realise that’s not quite the question you were asking but important to bear in mind)...

 

It varies. My parents were both sent letters with an appointment time, date and place (a vaccination centre). The letter did not state which vaccine they would be given and there was no contact number so no way of finding out. They didn’t know what they were getting until they arrived for their appointments (they both got AZ).

On the other hand my GP surgery contacted me to arrange my appointment so I was able to ask which vaccine I was being offered. As my GP surgery are doing separate clinics for the different vaccines I was able to book into the clinic of my choice (so yes I knew beforehand which vaccine I was getting). But I have no idea if other GP practices are managing things in the same way as mine.

 

@JaneL thank you for your reply, that's helpful to know. I also feel that my risk of relapse from covid itself is greater than the risk of relapsing from the jab. I'm shielding until I get the vaccine, just wondering if I'm brave enough to ask my GP if I can have the vaccine now. I'm erring on the side of trying I think.

@Sly Saint thanks for that link. I'd looked at the me association website but hadn't found this page!