Video: How do we know vaccines work?
And how do we know some medicines don’t?
We have produced our first animated video, which explains how medicines and vaccines are tested. Please feel free to distribute.
And here is a video by our partner organisation Community Media Trust encouraging vaccination. It is part of a series aimed at overcoming vaccine hesitation.
How do we know if medicines work?
Long ago doctors used to prescribe bloodletting to cure illness.
But no one had bothered to test it. The first American president, George Washington, probably died from bloodletting when he was ill.
You may have heard of the thalidomide scandal. Thalidomide was a drug marketed to treat anxiety and morning sickness. But it wasn’t properly tested. In the 1950s and 60s thousands of babies in many countries were born with deformities after pregnant women took thalidomide.
The thalidomide scandal led to much stricter tests for new medicines.
So, how do we know a medicine works, and that it’s safe?
We test them.
Before a medicine is used by people, it has to go through laboratory and animal tests to see if it has a good chance of being safe and effective against an illness.
Then there are usually three phases of clinical trials carried out by scientists. These trials involve human volunteers.
The scientists have to get the trial approved by an ethics committee.
They also register the trial on a website so that anyone can see what the trial is trying to do.
Then the medicine is given to about a dozen healthy volunteers to make sure it’s safe. This is a Phase 1 trial.
If all goes well, the scientists can move to phase 2. Here they give the medicine to many more people, and different types of people, at different doses. If it’s a vaccine they want to see what safe dosage makes people’s immune systems respond best.
If this goes well the scientists can move to phase 3. Here the medicine is tested in a Randomised Controlled Double Blind Trial.
It’s simpler than it sounds.
Let’s consider a vaccine against the coronavirus.
Thousands of volunteers are recruited.
By controlled we mean the scientists want to see what happens to people who get the vaccine compared to people who don’t.
The group that does not get the vaccine is called the control group. Instead, they get a placebo: a harmless substance that does nothing.
If the scientists only gave healthy people the vaccine and unhealthy people the placebo, of course the vaccine would do better. This is where randomisation comes in. To prevent the trial from giving biased or unfair results, the volunteers are randomly chosen to either be in the vaccine group or the control group.
Ideally, the trial is also double-blinded: Neither the volunteers nor the scientists know which volunteers belong to which group. This reduces the risk of people who get the vaccine being treated differently to those who don’t. It helps make the trial fair.
Then the volunteers are monitored over time.
A group of experts known as the Data Safety Monitoring Board frequently checks how the two groups are doing against each other. If the trial is double-blinded, only they can see the data. They also check for safety concerns.
At the end of the trial, if there were no big differences in the number of Covid infections or hospitalisations in each group, the vaccine is ineffective and it won’t be used.
But if there are a lot fewer infections or hospitalisations in the vaccine group, then the scientists can be confident it’s effective. Statisticians check to see if the difference between the two groups is unlikely to be due to chance. That’s what is called a statistically significant difference between the vaccine and control groups.
Because of randomised controlled trials we have medicines called antiretrovirals that help people with HIV to live normal, healthy and long lives. We also have vaccines that reduce Covid infections and deaths.
Trials also tell us when medicines do not work. For example, hydroxychloroquine and ivermectin have been proclaimed as wonder drugs against Covid-19. But trials have shown that they don’t work.
So there you have it: that’s how medicines are tested.
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