To vaccinate or not to vaccinate — that is the question

(TL;DR: vaccinate)

  • *Hazard warning– this post comes with Shakespearean puns**

And so we draw to a close a spectacular week in which we saw Margaret Keenan and William Shakespeare (what’s in a name?) be the first people of thousands to receive a Covid vaccine in the UK. At last there is light at the end of this long tunnel that we have been feeling our way through. The news brings hope to many, but also trepidation — how can these vaccines have been produced so quickly, and how can we know that they are safe?

It’s worthwhile remembering that not every person who is hesitant about getting vaccinated is conspiracy theory spouting anti-vaxxer. Vaccines are marvellous things but it’s a legitimate worry to be injecting a new drug into your healthy body without a great understanding of what it is, how it works, or how safe it is. So I’m going to try to address some of those questions now. Note that I’m a field epidemiologist — which means I’m not a vaccinologist, nor an immunologist, nor the type of epidemiologist who works on clinical trials. However, I’ve studied enough of those topics to be fairly conversant in them, and hope to be able to share some useful information to help you in your decision: to vaccine, or not to vaccine? I’m going to focus on the two vaccines currently most pertinent to the UK: the Pfizer vaccine, and the Oxford vaccine.

These are complex topics at the edge of my sphere of expertise, so I’ve included a few links for more info and would like to apologise to any immunologists or vaccinologists reading this post who are cringing as I murder their disciplines with over-simplifications — I’ll likely end up with more blood on my hands than Lady Macbeth.

Again, it’s a long post so feel free to jump to the bits that interest you specifically.


The immune system works by recognizing shapes — proteins. Every living thing is made up of various different formations of various different proteins, and the way those proteins hang together give each organism a unique shape. That can be at different scales — e.g. the shape of my face is unique to me, but so is my fingerprint. When the immune system comes into contact with a foreign protein, i.e. a shape it doesn’t recognise, something that doesn’t belong, it chunders into action to create an immune response. This involves a whole host of actions to beat the infection, including the production of antibodies that are tailored to recognise the specific shape of that pathogen. Once the infection is cleared, your immune system remembers that shape. If that same pathogen is then encountered again one day, the system can kick off the immune response without delay, giving you a headstart on clearing the infection before it can cause too much damage.

Vaccines work to imitate a shape that is unique to the pathogen in question , in order to trick the immune system into thinking that pathogen is around and trigger it to produce an immune response unique to that pathogen. Covid vaccines concentrate on the spike protein on the surface of SARS-CoV2 (the virus that causes Covid), which is the protein that the virus uses to get into our cells. The Oxford and Pfizer vaccines do this using different mechanisms.

The Pfizer vaccine is a mRNA vaccine, which is the first of its kind. Messenger RNA (mRNA) is essentially a little bit of nucleic acid code that tells our cells what proteins to make. Essentially, it’s like injecting a recipe for the SARS-CoV2 spike protein into your cells, and then your cells get busy making that protein. Once the recipe has been used, the cell destroys it, and you are left with a little bit of spike protein floating about in your cells, which is sufficient to trick your body into launching an immune response. This means that in future, if ever any bona fide, real life SARS-CoV2 comes along with its spike proteins ready to claw into your cells, your immune system will be ready to see it off.

This article from the CDC has a really nice description of mRNA vaccines.

The Oxford vaccine is an innocuous virus (an “adenovirus”) that can infect human cells but doesn’t cause disease, but that has been adjusted to have the SARS-CoV2 spike protein on its surface. This innocuous virus carries the spike protein into your cells, causing your immune system to trigger a response, and leaving you ready for the occasion of encountering the real-life SARS-CoV2 one day.

Professor Sarah Gilbert, who heads up the Oxford team, talks more about the extraordinary journey of developing this vaccine on this fab radio programme:


You’ll perhaps have heard various reports in the media of Pfizer being 90% effective, and Oxford being 70% or maybe 90% depending on dosing regimen, but in reality, the answer to this question is: it depends. The figures at the moment are about vaccine efficacy — how well the vaccines perform in the controlled experimental environment of clinical trials. What we really need to know is what the performance will be in real-life — the so called “vaccine effectiveness”, of these vaccines (that’s where the field epidemiologists, like me, come in — to study performance “in the field” rather than in an experiment). And there are still many questions that remain to be answered for each vaccine — how long will immunity last, what’s logistically more feasible to roll out at scale, which works best in different population groups, how well do they work to limit transmission as well as to limit severe illness etc. It’s likely we will end up having several Covid vaccines in use, each suitable for different population groups and settings — as is currently the case for influenza vaccines.

Still, the vaccine efficacy figures are encouragingly high for both vaccines. If you want to dip into the figures beyond the headlines, both Pfizer and Oxford have now published their trial results for your leisure and pleasure.

Pfizer —

Oxford —


I hold my hand up and say, I was firmly in the “there’s no way there’ll be a vaccine by the end of the year” camp; these vaccines have been developed at a truly phenomenal speed and is testament to what humans can collectively achieve if we set our minds to it. Necessity is the mother of invention. It’s no surprise, however, that some will find this speed unsettling. Here are some of the top reasons that explain why we now see people being vaccinated against a disease which has only existed for a year or so.

*Staff were redeployed

When Covid arrived on the scene, loads of scientists and allied professionals downed tools on their normal work and pivoted to Covid instead. This meant there was an unprecedented number of brains and hands working on Covid vaccines which cut the time needed to develop them. Imagine you want your house decorated. One painter might take ten days to get it done. Bring in ten painters, and it’d take one day. Similar story here.

*They were expedited

There’s a lot of stages to vaccine development and each phase usually follows another sequentially, with a lot of slow paperwork in between. For Covid, things have been run in parallel wherever possible and the associated paperwork sent to the top of the pile for completion. No steps have been missed, it’s all just been hurried along — like driving through a city where every traffic light is green.

*The vaccines were already in development

This is a big reason: we talk about work on Covid vaccines having been started the moment the virus arrived on the scene, but actually it had started way before that. We’d had coronavirus pandemic dress rehearsals before in the guise of SARS and MERS; mRNA technologies were already in development; and international protocols had already been established for “Disease X” — the name for whatever next pathogen was inevitably going to cause the next pandemic. So in fact, when Covid reared its head, a lot of the groundwork had already been laid to get a vaccine in production quickly.

*There were loads of volunteers

It can sometimes take a while to recruit to clinical trials, as not many people are up for getting novel drugs tested on them. Not so for Covid vaccines: people volunteered in their tens of thousands. To each and every one of those people: may I say thank you. We owe you a debt of gratitude.


All the usual trials have been conducted that would normally be conducted before a new vaccine goes onto market, amongst large study populations. As described above, the processes were expedited so that the whole end-to-end process was quicker, but safety was incorporated into each and every single step, as it normal procedure when developing any new drug or therapy. So these vaccines are as safe as any new vaccine that comes on the market in non-pandemic times. Both vaccine trials report excellent safety records, available in the links posted above.

Here’s a longer twitter thread dedicated to the topic of Covid vaccine safety:

Take home message: yes, the anti-vaxxers do protest too much, and yes, you can believe the nurse when they say “Tis but a scratch”.


This is where the Joint Committee on Vaccination and Immunisation (JCVI) comes in. The JCVI (not a very sexy acronym) is an independent expert group that advises the government on what vaccines should be included in the national vaccination programme and when they should be given. When I say independent, I mean they are independent *both* of pharma *and* of government. The committee is largely comprised of infectious disease specialists (academic and clinical), health economists, etc. They also have a lay member to represent the general public. Membership of the committee is *not* paid — they receive no funding either from pharma or government to be on the committee, although travel expenses and childcare are reimbursed by the Department of Health. All of their discussions and decisions are recorded in meeting minutes that are freely available to the public on the web.


It’s still too early to say. This will be the greatest vaccination programme we have ever embarked upon, and the roll out will bring huge logistical challenges. By starting with the most vulnerable groups, we will hopefully start to see the numbers of deaths beginning to fall and the pressures on the health service caused by severe Covid beginning to ease off, but it will still be some time before we see vaccination at high enough levels in the wider community that herd immunity would allow transmission rates to fall. So to paraphrase TS Eliott (rather than Mr Shakespeare this time): the pandemic will “end” not with a bang, but a whimper — and in fact, I would wager that Covid may always be with us, haunting our vulnerable in winter time, much like flu does.

Given the above, it is likely that we will have to continue with restrictions and altered behaviours for some months yet (altogether now: hands, face, space, limit contacts; meet outdoors/ventilate; hands-face-space; test-trace-isolate). Limiting spread over the festive period where we all tend to mix more is a particular concern — I wrote an article recently about celebrating safely if you’re looking for advice:

If the thought of continued restrictions is disappointing to you, think of it this way: a couple of weeks ago, we were in that dark tunnel, feeling our way along, with no end in sight. Now there is light; it may be a pinprick just at this moment — but we’re no longer feeling our way along blindly. We are now walking towards something. That is a different feeling entirely.

The BBC has published a great article on just this topic:


In a heartbeat. I am champing at the bit and have already begun to fantasise about hugging my parents the moment we are protected and it’s safe to do so. I literally cannot wait until the day I get a Covid vaccine, I could not be more excited by the prospect.


This has already been a very long post and yet I’m sure it’s only answered a few of your questions. These two podcasts are excellent in addressing some of the questions that we all have on our lips at the moment, I highly recommend a listen.

ZOE Covid app —

Dear Pandemic —

That’s all folks! Let’s all look forward to the day where there’ll be a plague on none of our households!! In the meantime — stay safe, and stay well xx.



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Georgia Ladbury

Georgia Ladbury

I’m an infectious disease epidemiologist with special interest in zoonoses, new & emerging infectious, One Health, and interdisciplinary public health research