What can deliberately infecting healthy people tell us about infectious diseases? How is this useful for developing treatments, and how do we manage the risks?
- Who is working on a vaccine to prevent COVID-19 (coronavirus disease)?
- When might a COVID-19 vaccine become available?
- This article was updated on 22 April to include the Government announcement of a new vaccine task force led by the Chief Scientific Adviser.
- The update also includes the announcement of Government support for a candidate RNA vaccine by the Department of Infectious Disease at Imperial College London and a candidate adenovirus vaccine by the Jenner Institute (University of Oxford) and the Oxford Vaccine Group.
- This is part of our rapid response content on COVID-19. You can view all our reporting on this topic under COVID-19.
- This article was originally published on 31 March and will be updated as the research progresses.
Vaccines are widely considered as the most effective public health intervention to protect people against infectious disease. When vaccine coverage in the population is high enough, the spread of infections can be reduced and, in some cases, eliminated.
The development of vaccines to prevent COVID-19 (coronavirus disease) caused by the new strain of coronavirus (severe acute respiratory syndrome coronavirus 2, SARS-CoV-2) is already underway. This involves creating a vaccine that will cause an immune response without leading to the symptoms of the disease, testing its safety and efficacy in people, and developing a manufacturing process. Typically, vaccine discovery and development can take 10 to 15 years. However, this process can be fast-tracked if there is adequate funding and flexible regulatory pathways to facilitate testing and licensing of new vaccines. There are also newer vaccine technologies that use genetic material and that can be developed and manufactured much more rapidly.
How do vaccines work?
Vaccines prime the immune system to respond rapidly to a later exposure to a specific virus or bacterium (pathogens). The immune system does this by recognising unique components of pathogens called antigens. There are several vaccine technologies to introduce antigens into the body to prime the immune system. For example, early vaccines used closely related pathogens that cause less serious disease (e.g. cowpox pathogens as a vaccine for smallpox). More recent approaches include the use of killed or modified virus, and the introduction of isolated viral proteins. One new technique involves the genes of the virus being carried into the body, often by non-pathogenic viruses. These allows for specific antigens to be produced in the body without exposure to the virus in question.
Developing a COVID-19 vaccine
Scientists in China took a sample from a patient with COVID-19 and published the genetic sequence of the virus in January. This genetic recipe gives researchers crucial information about the evolution of the virus, the mechanisms through which it causes infection, and the genetic sequence of antigens that can be used in vaccines to stimulate an immune response. Previous work on vaccines for related viruses, such as Middle East respiratory syndrome coronavirus (MERS-CoV), has given scientists a head start.
The safety and effectiveness of vaccines are thoroughly tested before they can be licensed for general use. Like other new medicines, vaccines are developed in two broad stages:
A discovery stage to identify antigens, create and test vaccine candidates in the laboratory, and to develop manufacturing protocols.
This comprises four stages:
A small group of healthy people (<100) is given the vaccine to make sure there are no safety concerns, to see how well it stimulates an immune response and to work out an effective dose.
The vaccine is tested in a larger group (several hundred people) to see whether the vaccine works consistently, to assess the immune response and to look for side effects.
The vaccine is studied on a much larger scale (several thousand people) under natural disease conditions. This produces enough data to identify rare side effects and to evaluate how well the vaccine works in the real world; does it generate enough immunity to prevent and reduce disease?
Manufacturers apply for a license from regulatory bodies so that their vaccine can be marketed for human use.
After licensing, research continues to monitor any adverse effects and to determine long-term effectiveness.
Vaccine manufacture is a complex biological process. The rate at which doses of a vaccine can be made depends on how quickly the antigen can be made, or the genetic material that triggers antigen production in the body, and how much is needed in each dose. Special techniques can be used to maximise the number of doses from a given quantity. Batches of vaccine must also meet rigorous standards, to ensure consistency and quality.
Delivering vaccination programmes
It is expected that new COVID-19 vaccines will take 12–18 months to become commercially available, although it is likely that they could be made available earlier for emergency use, such as in healthcare workers or at-risk groups. It is also unclear what volume of vaccine could be made, although researchers engaged on current vaccine developments estimate that production for some could be at the million-dose scale by the end of 2020. Decisions about how to prioritise who will receive COVID-19 vaccine(s) are a key consideration. In the UK, this is the role of the Joint Committee on Vaccination and Immunisation (JCVI) which makes recommendations to the UK Government on national immunisation programmes.
The latest COVID-19 vaccine research
On 23 March, the Government pledged £20m to the global Coalition for Epidemic Preparedness Initiative to fast-track vaccine development. This was followed by an announcement of an additional £210m, after the meeting of the G20 Leaders on 26 March. On 17 April the Government announced a new vaccine taskforce led by the Chief Scientific Adviser, with representatives from academia and industry. The taskforce seeks to support the rapid development of a vaccine, by facilitating rapid clinical trials, supporting testing and manufacturing capacity, reviewing regulations where necessary and developing plans for procurement and delivery of any successful vaccines.
Key highlights from UK research include:
- The Jenner Institute (University of Oxford) and the Oxford Vaccine Group has developed a vaccine made from a harmless virus (an adenovirus) altered to produce an antigen – in this case a club-like spike protein – found on the surface of the coronavirus. The vaccine is called ChAdOx1 nCoV-19. The team is recruiting 510 healthy volunteers aged between 18 and 55, for phase I clinical trials. Volunteers will receive an intramuscular injection that contains either the new vaccine or a control injection (in this case a meningitis vaccine, MenACWY). This is a single-blinded study, meaning that the volunteers will not know which injection they have received. The first tests in people are scheduled to begin on 23 April The subsequent plan for testing involves a phase II trial which includes a group of adults aged 55-70 years, then the over 70s. The final phase III trial will involve 5,000 volunteers, half of which will receive the COVID-19 vaccine. Volunteers from earlier phases will be included in this part of the trial. While the best-case scenario is that results from the phase III trial could be available by autumn 2020, this is highly uncertain and subject to change. The Government announced a £20m investment in this project on 21 April.
- Another University of Oxford project seeks to develop manufacturing processes at a large scale (million-dose scale), so that sufficient quantities with which to immunise high risk groups can be produced as quickly as possible.
- Public Health England scientists based at Porton Down have produced synthetic versions of the virus, this will support evaluation and testing of vaccines and treatments for both UK and international projects.
- The Department of Infectious Disease at Imperial College London has developed a candidate RNA vaccine. The vaccine works by instructing cells to make a protein found on the surface of coronavirus, to trigger an immune response. Tests in animals have shown that the vaccine stimulates antibody production. The Government is supporting this project, with a £22.5m investment announced by the Health Secretary on 21 April. The next step is to test the vaccine in people; this is expected to begin in June.
Other international projects are in, or about to enter Phase 1 trials, with many others in preclinical development.
- In the US, the National Institute of Allergy and Infectious Diseases (part of the National Institutes of Health) and the company Moderna have developed a candidate vaccine that uses messenger RNA (mRNA) technology. mRNA is a molecule that instructs individual cells to build specific proteins; in this case one found on the surface of the SARS-CoV-2 virus. The vaccine is in the first phase of testing in people: 45 healthy adults will receive the vaccine with the first results are expected in late April. Initial results will indicate how well the vaccine can induce an immune response, and to evaluate the effect of different doses. While the vaccine is unlikely to be commercially available in the next 12–18 months, there is the possibility that it could be available for emergency use such as in healthcare workers by autumn 2020.
- The US Company Inovio has designed a DNA vaccine (INO-4800) against COVID-19 which has completed pre-clinical development. The vaccine will be tested in more than 30 adults in in the US in mid-April, subject to regulatory approval. Results of human clinical trials are expected in autumn 2020, and the company anticipates that it could produce 1m doses by the end of 2020.
- In Germany, Curevac has announced that is developing COVID-19 vaccine candidates using mRNA technology. They expect to start Phase 1 testing in early summer 2020 and to report initial data 30 days later.
- In China, CanSinoBIO has an adenovirus vaccine (Ad5-nCoV) ready for Phase 1 trials. The vaccine will be tested in 108 adults in April. They are currently recruiting participants.
You can find more content from POST on COVID-19 here.
How do our bodies defend against Covid-19? Read how immune responses differ across people, variants, reinfection, vaccination, and current immunisation strategies.
Research studies involving thousands of people have allowed scientists to test which drugs are effective at treating COVID-19. Several drug therapies are now available to treat people who are in hospital with COVID-19, or to prevent infections in vulnerable people becoming more serious. This briefing explains which drugs are available, the groups of people in which they are used and how they work. It also outlines the importance of monitoring the emergence of new variants and drug resistance.