There are all sorts of vaccines
for lots of different diseases but conventional vaccines
all share some common ingredients.
So, other than water, what are they made of?
I asked professor Adam Finn to explain.
He was involved in the Oxford AstraZeneca vaccine work
and he knows a lot about vaccines.
There's nearly always a little bit of
or maybe even all of a microbe that would normally
cause an infection to make you sick
but this time it's just going to make the immune response
without making you sick.
The part that is most commonly used is the protein on the outside of a microbe
which is called an antigen.
So what else is there?
So there'll be some kind of a preservative
in there that basically stops the vaccine from containing
something you really don't want to get
and the other thing that might be in there is something to just tweak your immune system
into action.
So it just kind of triggers things off
and makes you get that protective response.
Those last things he mentioned are called adjuvants.
Not all vaccines have or need adjuvants
but when they are sometimes present,
they can help a vaccine achieve the best efficacy possible.
In many cases, without an adjuvant, the vaccine simply just doesn't work,
it doesn't give you protection so the body just ignores it,
it doesn't see it as a threat and nothing happens.
The other point is that you can actually use less of the antigen that you need to put in
there by putting in the adjuvant and if there's a shortage,
it means that you can spread it over
a much larger number of people and get more people immunised
for the same amount of vaccine.
Those are the main elements of a vaccine.
Antigens, preservatives and adjuvants.
But then you've also got your stabilisers to keep the antigen from changing
and there's also something called residuals which are basically just the things left
over from the manufacturing process.
But these are only present in vanishingly small traces.
That's what's inside a vaccine.
But what happens when you put all these things inside your body?
How does it react?
Cells in your body that are trained really to look for foreign material
in places where it shouldn't be.
They're scouting around looking for that foreign material
and they scoop it up and then they carry it off to areas called lymph nodes
and that's where the immune
response starts to happen
and your body responds to that and it builds up cells and antibodies
that will neutralise that foreign material
and that will protect you if you then subsequently
get exposed to that infection whether it's a virus or a bacterium
and your whole body will be prepared
to react to that when it arrives and the way that it wouldn't have been if you
hadn't had the vaccine.
So what about the Covid jabs?
Do they work like conventional vaccines?
There are a few different ones around and they work in different ways.
So we're just going to focus on the covid vaccines
that have already got approval in the UK.
That's the Oxford AstraZeneca vaccine which involves DNA,
then there's the Moderna vaccine and the Pfizer/BioNTech vaccine
which both involve mRNA.
But I'll let Adam explain how that works.
So these vaccines are also different in the sense that you're not giving little bits of the
microbe or even the whole microbe
what we're doing instead is we're giving the genetic code for one
part of the virus and then letting our own cells make the bits of virus that we then respond to
by giving them the code to do that.
So the ones we're using right now, those ones don't have adjuvants,
they don't have preservatives in and they do need to get used pretty quickly after you
take them out the fridge for that reason.
These three covid jabs just don't need a lot of the ingredients
that we've mentioned because like Adam says, these vaccines are not delivering
a covid microbe into the body.
Instead, they're helping our own cells make something that looks the same as
a covid viral spike protein so that our immune system can respond to it.
The only ingredients they do share with other more common vaccines
are salt water and sugar,
so does this mean they're safer?
Old-fashioned vaccines are things that we use for a very long time
when we know a lot about them
whereas these new ones, they're new.
They're pretty straightforward, they seem to
work much better than any of us expected them to
and we've gone in the last couple of months from
a few tens of thousands of people and not seen any problem to many millions of people now in
this country and in some of the other countries around the world
and again no problems so far.
They are no less safe than conventional vaccines
but they are much more straightforward
in the sense that they require fewer ingredients to work effectively
which is a credit to the scientific work that made them possible
but they're also new and like all new thing in science,
it takes time to accumulate data
to better understand how well they work.