What is a vaccine?

A vaccine is a type of medicine which helps the body’s immune system to recognize and fight an infectious disease it has not come into contact with before. Vaccines are one of the most effective methods to prevent infectious diseases, and they have been estimated to prevent up to 3 million deaths a year globally. We currently have vaccines against more than 25 serious and potentially life-threatening diseases.

How do vaccines work?

When the immune system is exposed to a new disease-causing organism such as a virus or bacteria, as it fights it off, it also learns to recognise that organism. This means that if the person is exposed to the same organism again, the immune system can quickly make antibodies to attack it, and protect the person from getting sick and spreading the disease.

Vaccines take advantage of this, and “train” the immune system using small amounts of the weakened or dead virus or bacteria, their proteins or genetic material, that cannot make you sick.

How are vaccines made and tested?

Vaccines must go through several stages of testing to make sure they are safe and work well. The main stages are:

  • “Discovery and pre-clinical” phase – at this stage researchers work out how best to make a vaccine for the organism, and test it in the laboratory and on animals.
  • “Clinical phase” – if the vaccine gives promising results at the pre-clinical phase, it can go on to be tested in people, but there are still multiple stages the vaccine needs to pass:
    • Phase 1 – the vaccine is first tested on a small number of healthy people (10-50) who are monitored very closely to check that the vaccine is safe and to test whether it causes an immune response
    • Phase 2 – the vaccine is then tested on more people (hundreds) and the immune response is studied in more detail; researchers continue to monitor for any adverse effects
    • Phase 3 – the vaccine is tested in thousands of people to see if it protects them from catching the disease; researchers continue to monitor for any adverse effects

Vaccines normally need to successfully pass each phase before they can pass on to the next, and many vaccines fall at one of these hurdles. Once the vaccine passes the initial stages, the makers also need to make sure they can make large quantities of the vaccine to very high standards.

If all these trials suggest that a vaccine works and is safe, the data must be independently assessed, and the vaccine approved for sale by each country’s medicines regulatory body.

From start to finish, this process can take more than a decade to complete and cost hundreds of millions of dollars. Even after a vaccine is launched, the manufacturers and regulator monitor in case there are rare side effects.

What’s different about coronavirus vaccine development?

Because of the huge adverse impact, the COVID-19 pandemic continues to have globally, it is hoped that a vaccine against the novel coronavirus could be developed in 6-18 months.

This will mean carrying out some of the different testing stages at the same time, rather than one after the other. Some pre-clinical studies might also be skipped if this can be done without compromising safety.

Funders are also trying to fund different research groups trying to develop vaccines using different approaches, to increase the chances that at least one of these will work. Manufacturing sites will also need to be developed early, and in sites around the world, so that if we get a successful vaccine, it can be produced and distributed rapidly, to protect as many people as possible.

Developing the vaccine in this rapid way will require billions of dollars in investment.

What stage has coronavirus vaccine development reached?

On the 30th of May, according to the World Health Organization (WHO) there were:

  • 10 potential COVID-19 vaccines in the clinical phase of testing
  • 121 potential COVID-19 vaccines in the pre-clinical phase of testing

Potential vaccines are being developed worldwide, with 46% being developed in North America, 18% in Europe, 18% in Asia and Australia and 18% in China.

The vaccine in the most advanced stage is being developed by the University of Oxford, in collaboration with AstraZeneca. Initial studies in animals suggested that the vaccine was safe enough to be tested in humans. The vaccine started phase 1 testing in late April, which involved more than 1,000 healthy adults being given the vaccine.

The researchers are now moving on to phase 2/3 testing, and are aiming to recruit over 10,000 volunteers. The first part of the study (phase 2) will include small numbers of children and older adults, who were not included in phase 1 testing, to see how they respond. The phase 3 part of the study will be the larger part of the study and only assess adults. Vaccinations for phase 2/3 started in May.

The researchers may get the first signs on whether the vaccine works by mid-June this year. However, if transmission of the virus in the UK slows, getting results from the phase 2/3 trial could take up to 6 months.

The Oxford team stated that they expect to produce a million doses of the experimental vaccine as early as September. This is to ensure that if the trials do show that the vaccine works, there will be doses of it ready to be used.

Analysis by EIU Healthcare, supported by Reckitt Benckiser


Reading list

  1. Health topics: Vaccines. https://www.who.int/topics/vaccines/en/ (Accessed 1 June 2020)
  2. Draft landscape of COVID-19 candidate vaccines. 30 May 2020. Available from: https://www.who.int/who-documents-detail/draft-landscape-of-covid-19-candidate-vaccines (Accessed 1 June 2020)
  3. US CDC. https://www.cdc.gov/vaccines/vpd/vpd-vac-basics.html
  4. Vaccine knowledge project. University of Oxford. https://vk.ovg.ox.ac.uk/vk/how-do-vaccines-work
  5. US Department of Health & Human Services. Vaccines.gov https://www.vaccines.gov/basics (Accessed 1 June 2020)
  6. NHS UK. Why vaccination is safe and important https://www.nhs.uk/conditions/vaccinations/why-vaccination-is-safe-and-important/
  7. BBC Newsnight. Coronavirus: The race to develop a vaccine. 15 May 2020. Available at: https://www.youtube.com/watch?v=V8jhlaep0Ww&t=369s
  8. How can we develop a COVID-19 vaccine quickly? 22 April 2020 https://wellcome.ac.uk/news/how-can-we-develop-covid-19-vaccine-quickly (Accessed 1 June 2020)
  9. The Telegraph. University of Oxford coronavirus vaccine: everything we know so far. 1 June 2020 Available at: https://www.telegraph.co.uk/global-health/science-and-disease/oxford-trial-covid-19-coronavirus-vaccine/ (Accessed 1 June 2020)
  10. Oxford University. Oxford COVID-19 vaccine to begin phase II/III human trials. 22 May 2020. http://www.ox.ac.uk/news/2020-05-22-oxford-covid-19-vaccine-begin-phase-iiiii-human-trials (Accessed 1 June 2020)