How we know vaccines are safe
Опубликованно 02.09.2020 09:57
There are 31 vaccine candidates being trialled around the world, all in different phases, according to the World Health Organisation.
There are a further 142 in preclinical evaluation, including one at the University of Queensland.
With talks of COVID-19’s vaccine becoming mandatory in Australia, many are questioning its safety. So how does a vaccine clinical trial work?
Brisbane’s Mater Health Services infectious diseases director Paul Griffin said trials were conducted in four phases to ensure the safety of participants and that the process was cost-effective.
Data from each phase was analysed and must show safety and effectiveness before progressing to the next.
“While most vaccine studies are relatively long clinical trials, often around six to 12 months, safety and efficacy can often be established earlier than the end of the study,” Associate Professor Griffin said.
“The later assessments are then used to demonstrate how long the protection from the vaccine is likely to last.”
Associate Professor Griffin said clinical trials typically took many years, mainly because of the cost associated with each step and that the time and money for each phase was not invested until the previous stage was complete and proved the desired safety and efficacy.
“In the case of COVID-19, we have been fortunate to see sufficient investment that has enabled planning for all phases of clinical trials to take place at the beginning, allowing the next phase of clinical trials to commence quickly,” he said.
“This has meant that we are seeing vaccine development happen at a rate much faster than ever before without compromising at all on any of the usual processes required to be certain about the vaccine’s safety, as well as how well it is likely to work.”
Associate Professor Griffin and the Australian Science Media Centre have broken down what happens in each phase:
PRE-CLINICAL
Strong evidence from labs and animal studies is looked at before a vaccine is considered for human trials.
This is so investigators and an independent ethics committees can be confident it is very likely to be both safe and effective.
PHASE 1
These are relatively small trials with about 100 volunteers to confirm the safety already strongly expected from the animal trials.
Blood tests are collected to test the vaccine’s effectiveness in the lab and give an indication if the vaccine has generated an immune response. Although this information is useful, it doesn’t guarantee it’s going to work.
Multiple doses are often used to try determine the ideal amount to take into the next phase.
PHASE 2
While this phase still mostly focuses on safety, the number of subjects increases by 1000 or 2000.
Studies look more closely at the protection from the pathogen in question.
While giving the first look at protection here, the subject size is not large enough to confirm if the vaccine protects people from the infection.
PHASE 3
This is the final phase before a vaccine is approved for widespread use.
These trials primarily demonstrate if those who have received the vaccine have significantly lower rates of infection than those that don’t.
This phase typically needs tens of thousands of volunteers. The number depends on a range of factors, including how widespread the infection in question is.
While vaccines can fail to show effect and not progress to further stages, phase three is where a number of trails prove unsuccessful for failing to provide sufficient protection.
PHASE 4
Once the vaccine is in widespread use, data is collected on its safety and how well it has worked and is continued to be collected.
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