How is a vaccine created, broadly speaking?
Vaccines go through extensive testing and trials before they’re anywhere close to being used on people - so even after they’re created there’s a lot of work done behind the scenes before we ever get a jab.
Broadly speaking, a vaccine is created by isolating a weakened form of a pathogen (disease causing nasty) or a component of it so that our immune system gets a safe intro. This introduction might be in the form of a vaccine containing a small amount of a weakened (what we call ‘attenuated’) living virus or bacteria, such as the vaccine for Measles. With other vaccines however this immune style handshake is to a small part of the disease causing bug or some genetic coding to let the body produce one - these can be a specific protein or component found on or within a virus, for example. Either option means our immune system learns to recognise a specific pathogen safety and it’s thus geared up to knock it back if we get exposed to the real deal in future.
Alongside the necessary immune triggering component, vaccines might also include a variable number of compounds that help stabilise & assist the vaccine itself. Just like the star of the show (the pathogen component), these are all tested extensively for safety and use.
After a vaccine has been created, the next vital stage is trailing it to ensure it’s safety and effectiveness is all there. Like all medicines, this occurs through a number of rigorous steps and stages that seek to test whether a vaccine works, what any common side effects are and (of course) whether it’s safe.
Phase 1 trials occur when the vaccine is given to a small number of (usually) healthy young adults to test that it creates the required immune response and that it’s safe.
Phase 2 trials then step things up to a larger number of people, which can include those for whom the medicine or vaccine is ideally intended for and a group who get an inactive substance to compare. A large number of stages occur in phase 2, and it’s about trialing safety and effect. Stage 3 trials include a much larger (thousands) number of people across multiple groups and countries, where fine tuning of results and outcomes is analysed.
What happens when you are injected?
Broadly speaking, being injected with a vaccine is akin to a bit of a 'first date' for the immune system. When we get a jab, it’s about introducing a small amount of a disease causing pathogen (i.e. the virus or bacteria) to our body so that we can generate an immune response to fight it in a safe way.
In all cases, the goal here is letting our body get a primer so it’s ready if and when the main event occurs. When we receive a vaccine our body is triggered into an immune response against the foreign item - in weeks to days it gets to work creating factors (you’ve probably heard terms like ‘antibodies’) to fight the real deal if we ever come into contact. That all means we’re either much less likely to catch an illness in the first place, and/or an infection is much less severe if we do.
It’s the reason why we also might feel a bit worse for wear or briefly unwell after we get a vaccine - symptoms like a headache, feeling tired or getting mild fevers/sweats aren’t because the vaccine is doing us harm, they’re side effects to our immune system doing it’s thing and generating a response.
An effective vaccine is one that leaves our body with a game plan for knowing how to recognise, raise the alarm and then fight off a specific type of virus or bacteria. Once you’re injected this process begins near immediately, but it can take some time (up to several weeks) for the body to do it’s thing and be ready.
In essence it means we’re primed to hit back on a disease causing agent if and when we meet it in the real world. Some vaccines mean we can then knock it back before it ever takes hold (thus don’t catch it), while others mean if we are infected the outcome is much less severe.
Can you actually get sick from a vaccine?
For individuals with normal healthy immune systems, the broad answer here is no. The foundation of a vaccine to begin with is that it primes our immune system to recognise and attack a bug, without actually causing or giving us the disease.
Vaccines that contain live but weakened forms of virus or bacteria (such as the Measles vaccine) generate an immune response without actually being able to infect us or make us sick like the real thing. They can in rare instances (such as in those who have a weakened immunity) get out of hand and cause illness, but it’s why they’re not used on those with these risks.
For vaccines like those for COVID-19 or Influenza, there is no chance of these actually causing illness, making us sick or giving us the Flu as some might claim. The science means this is basically impossible as we’re not being jabbed with the virus itself.
Many people have questioned this online because they’ve noted feeling briefly ill after their COVID vaccine. Feeling off colour or a bit sick after a vaccine isn’t because you’ve been given the disease, it’s because things like headaches, tiredness, fevers and tummy upset can be side effects of our immune system responding and doing its thing.
Can you still get the illness you are vaccinated against? Why?
This one’s a bit complicated as whether we can still become infected by something after a vaccine depends on the bug itself, the vaccine & on individual factors that might impact how our immune system responds. In a nutshell though, it’s a yes and a no.
The gold standard for any vaccine is that it prevents infection full stop. When a vaccine does this it’s termed ’Sterilising Immunity’ and it stops bugs dead in their tracks. The Smallpox vaccine works this way, and it’s why the disease has basically been eliminated worldwide.
For most vaccines however, being vaccinated does still mean there’s a risk of infection yes. The type of immune response we generate to a vaccine and how effective it is influences this, and so many pathogens can still infect us even if the immune system then mounts the attack from there. Bugs that change their form or mutate (i.e. the flu) are also ones where risk of infection even after a vaccine might occur.
Even if a vaccine doesn’t fully stop people picking up an illness it doesn’t mean it’s not still absolutely worth while. Just as we’ve seen for COVID-19, those who are vaccinated are often far less likely to suffer a severe or life threatening form of the illness, and data shows that many vaccinations like this help make passing it on to someone else much less likely too.