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How do vaccines work?
Vaccines work! They have transformed the biosciences and the fight against illness, worldwide.
The Lancet reported, in 2021, that vaccines administered against ten specific diseases had saved more than 37 million lives, globally, between 2000 and 2019. They predicted that number would rise to 69 million lives by 2030 and, of course, that figure couldn’t factor in the extraordinary success of the COVID-19 vaccines during 2021 and ’22.
As we discussed in this article, ALLpaQ is proud to be a critical supplier to various vaccine manufacturers around the world, supporting scientists in the crucial work they do.
It’s a never-ending battle and the scientists and engineers working in the biosciences, developing, manufacturing and delivering these life-saving vaccines, they’re big pharma’s SWAT troops and, when it comes to bacteria and viruses, they’re taking no prisoners!
But, despite widespread knowledge of the benefits of vaccines – especially in response to the unprecedented global pandemic – there’s still a lot of confusion, in the public, about how vaccines work.
So, let’s break it into bite-size, easy-to-digest chunks
A brief history of vaccines
For thousands of years, human civilisation was at the mercy of infectious disease. In the 1340s, for example, a bubonic plague wiped out up to half the population of Europe and Asia.
By the 1700s, physicians began to notice that those who survived certain infections, such as smallpox, became immune to further infection.
Scientists began to. But, how to use this knowledge medicinally, without running the risk of killing the patient?
In the 1790s, the British physician, Edward Jenner, noted that milkmaids were getting infected with cowpox, which was making them immune to the frequent smallpox infections that would blight the community.
He understood that the body can learn to defend itself against some illnesses, once it has experienced them.
From this, he developed the world’s first vaccine, when he successfully infected people with a fairly benign, cowpox virus to help immunise them against the far more deadly smallpox.
To this day, we still use the word ‘vaccine’, which derives from the Latin for cow.
Almost a hundred years after Jenner, Louis Pasteur took the cowpox idea – of introducing one type of pathogen into the system, to produce a reaction that would protect the body against a related pathogen – and applied it to rabies.
Thus the science of immunology was born.
How does our immune system work?
But, why did that whole cowpox/smallpox thing work?
Brace yourself – here comes the science bit:
Vaccines work because our body’s defences can learn from experience! Vaccines essentially train our immune system like a Regimental Sergeant Major to identify pathogens and attack them.
Our Adaptive Immune System is a crack unit of specialist cells – which work together to combat invading pathogens.
Firstly, they recognise a new virus or bacterium that has entered the system by mapping its molecular markers – called antigens.
Next, they produce antibodies to bind with and destroy the antigen on the pathogen. Phagocytes can then come along and consume the damaged pathogen and that’s how our adaptive immune system troops confront and overwhelm an invading illness.
Each antibody is designed to recognize just one specific antigen. A healthy immune system has innumerable different bespoke antibodies in its armoury and (as the US Deptartment of Health states here) there can be as many as one quintillion – that’s one million trillion – individual antibodies floating around inside us at any one time.
Once the immune system has responded to an antigen, it also produces an army of long-lived Memory Cells, which remain alive in the system, ready to produce the antibodies again if the pathogen reappears.
It is these Memory Cells that give us our immunity.
So, how do vaccines work with our immune system?
Vaccines work with this system by activating our Adaptive Immune System and making them believe an infection has happened, so they go through the motions and produce the all-important protective antibodies.
Vaccination is a safe method of introducing antigens into the system for the immune system to practice on and, therefore, prepare for the arrival of the real thing.
There are several different types of vaccines already in use, with many new technologies in development – such as Attenuated Live Vaccines which produce a response by introducing a deliberately-weakened version of the pathogen into the system. This is, as the name suggests, a live pathogen – which will produce a strong immune response from the body but is not typically strong enough to create actual illness.
Alternatively, Recombinant or Subunit Vaccines are engineered to use select parts of the pathogen – the antigen – to activate the immune response. These vaccines are safer to use, even for people with weakened immune systems.
Genetically engineered vaccines, like these, are increasingly the way forward for the technology!
The future of vaccines?
As you might expect, the future of vaccines is genetically engineered. For example…
Nucleic Acid-Based Vaccines – or ‘DNA Vaccines’ – isolate the genes which go into the specific antigens needed to create an immune response. These genes leave out any of the harmful parts of the pathogen and can create a stronger immune response – armour-plating the body against any future threats.
Similarly, RNA Vaccines use Messenger RNA molecules, which tell cells to build very specific antigens. An mRNA vaccine can be produced rapidly and more cheaply than traditional equivalents, making them an appealing solution. Also, like DNA Vaccines, they don’t use the infectious elements of the pathogen, so can be safer for vulnerable patients.
If you want to know how these work in practice – both the Pfizer-BioNTech and the Moderna COVID-19 vaccines use mRNA.
But, beyond creating better and safer vaccines, there are various restricting factors when it comes to delivering those vaccines which have already been successfully developed – such as in countries which have poor healthcare infrastructure, which simply can’t afford to buy-in existing vaccines, or for which maintaining a cold-chain is problematic.
Therefore, there is a drive to find cheaper, safer, more effective and more easily administered vaccines.
Getting away from the needle
Inhaling a vaccine through a nasal spray, for example, is a method already in use, in some places, for Influenza.
Administering vaccines through a patch – either microneedle patches or non-needle patches – is also an exciting development because, unlike anything involving syringes, this wouldn’t require the presence of a trained medical professional.
This would also help overcome an additional obstruction to uptake of vaccines – particularly in the developed world – a growing fear of needles. This affects between 25% and 65% of children and continues to affect 10% of adults. So, clearly, there would be medicinal benefits for any delivery method which avoided needles.
There you have it, then. That’s how vaccines are working, inside you, right now!
