Why is it taking so long to develop a vaccine against COVID19? What are all these phases and clinical trials?
Many scientists and researchers have hypothesized that the COVID19 pandemic will end or at least have a global downward trend when we are finally able to produce a vaccine.
Vaccination with enough coverage would reduce the number of cases and help prevent the ongoing spread of COVID19. With enough coverage, even those who can’t get vaccinated would be protected through #herdimmunity (see our post here)
At the time of writing, 10 vaccine candidates have made it to phase 1 and one candidate into phase 2 of clinical trials and over 115 candidates are in the preclinical evaluation stage. Vaccine candidates are being developed by universities and businesses such as pharmaceutical companies.
So what do the phases of a vaccine clinical trial mean?
Pre-clinical development – this stage occurs in laboratories where researchers create the vaccine concept and then evaluate if that concept will produce the desirable effect in test tubes and in animals.
The new vaccine then has to meet some basic criteria in safety, purity, potency and efficacy and is sent for evaluation to a regulatory agency for medicine and healthcare products, for example the Food and Drug Administration (FDA) in the United States or the European Medicines Agency (EMA) for European Union countries.
Clinical Development is broken into four main progressive phases.
Phase 1 of clinical trials (where five of the COVID19 vaccine candidates currently stand) is the first stage. It involves small scale trials on 5 – 50 healthy volunteers to check if the vaccine is safe to humans and if it induces immune responses.
Phase 2. If the vaccine is deemed safe after phase 1, it moves on to phase 2, where a larger number of volunteers, normally in the hundreds, are given the vaccine. Volunteers at this stage can be recruited among people with higher risk of contracting the infection, such as healthcare workers. This stage aims to evaluate efficacy of the vaccine – a fancy word to see if the vaccine produces the desired and intended result. Vaccine safety, side effects and the immune response of the volunteers, also continue to be assessed. Vaccine dosage and route of administration can also be investigated.
Phase 3. If a vaccine candidate proves its efficacy in phase 2, it moves on to phase 3, which is the most expensive and lengthy of the phases. The main aim of phase 3 is to see if the vaccine confers protection in “natural” conditions in larger groups of people of different ages and conditions and living in different contexts. Thus, it is normally a “multi-centered” trial, e.g. it happens in more than one country, hospital or area.
If possible, because of ethical or logistical concerns, it can be conducted in a double or single blind placebo controlled randomised manner. That is, volunteers are allocated to receive the vaccine or a placebo in a random manner (by chance), and neither the volunteers nor the people running the study know who receives what until the trial is over (blinded study).
The safety and immune responses to the vaccine continue to be assessed.
Licensing. Once all the data from Phase 3 is collected it can be sent to the regulatory body for licensing – licensing is given once it is proven that the vaccine is effective and safe and the benefits outweigh the risks.
The vaccine can now be rolled out to the public.
Phase 4 – The work is not over once the vaccine is rolled out to the public. Phase 4 is “post-marketing surveillance”. It aims to detect and share information about rare adverse effects that may still occur as more and more people receive the vaccine, and that weren’t captured in the first three phases. It also continues to assess the long term efficacy of the vaccine.
So when does the average person get the vaccine?
That’s a hard question to answer at the moment – scientists have been interviewed saying that they are 80% confident that they will have a vaccine ready by September and other sources believe it will take 18 months or 2 years.
While this may seem like a very long time, ever before in history has vaccine development progressed so quickly. The World Health Organisation Director General Dr. Tedros Adhanom Ghebreyesus announced on March 18 that ‘the first vaccine trial has begun, just 60 days after the genetic sequence of the virus was shared by China.’ This is truly a fantastic achievement. There is high hope that a vaccine against COVID19 virus can be developed much faster than ever before.
If you wanted to stay up to date with the vaccine trials as they advance through the phases the London School of Hygiene and Tropical Medicine has a great vaccine progress tracker.
Bill Gates has an excellent article explaining, among other things, the challenges to roll out a vaccine globally once one candidate has been licensed.
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