What are the challenges to developing a vaccine?
The virus that causes Covid-19, SARS-CoV-2, is new. Scientists still do not fully understand it. Key questions to be answered include:
- Does the presence of Covid-19 antibodies in the immune system protect against future infection?
- Can a person be infected for a second time with Covid-19? If so, is the second infection different from the first?
- How long will Covid-19 immunity last?
A summary of studies published in medical journal The Lancet states that 90% of hospitalised patients develop antibodies within the first two weeks of symptomatic infection. However, the summary also notes that data from non-hospitalised individuals with either mild or non-existent symptoms is much less readily available. Considering the data that has been gathered, the authors state that:
“It seems likely that natural exposure during this pandemic might, in the short to medium term, not deliver the required level of herd immunity and there will be a substantial need for mass vaccination programmes.”
Vaccines usually take years to develop, manufacture and deliver to a population. The urgent need for a mass vaccination programme for Covid-19 presents major challenges, including:
- Uncertainty around antibody-dependent enhancement, which occurs when antibodies intended to fight an infection actually worsen it;
- Global supply chain issues damaged by lockdown measures; and
- Risk involved in scaling up production capacity sooner than vaccine producers are accustomed to.
What are the current vaccine candidates?
According to the London School of Hygiene and Tropical Medicine’s vaccine tracker, as of 22 June there are 195 candidates for a Covid-19 vaccine. The World Health Organisation (WHO) publishes a regularly updated landscape of the progress of these projects. As of 22 June, 13 vaccine candidates have reached the clinical evaluation state of development.
University of Oxford/AstraZeneca
According to the WHO, the vaccine in development at the University of Oxford, in partnership with the pharmaceutical company AstraZeneca, is the candidate currently in the furthest stage of development. The vaccine is made using a weakened version of the adenovirus known as ChAdOx1. To ensure that no prior immunity to the vaccine exists, a strain isolated from chimpanzees that does not circulate in humans is used.
Human trials for this vaccine are already underway. Over 1000 people took part in the phase one clinical trial, receiving either the full vaccine or an active control (a meningitis vaccine called MenACWY). Phase one vaccinations were completed on 29 April. Phase two will involve testing the vaccine on a small number of older adults and young children. Phase three will expand the scale of the testing significantly and will involve around 10,000 participants of all ages. Both phases were due to take place throughout May and June.
Pascal Soriot, chief executive of AstraZeneca, has stated that he expects the vaccine to provide “about a year” of immunity from Covid-19. Soriot added that “if all goes well, we will have the results of the clinical trials in August or September”.
Moderna/National Institute of Allergy and Infectious Diseases
American biotech company Moderna’s vaccine candidate entered phase one clinical trials on 16 March. Phase two trials, with 600 people, began in late May, with phase three expanding to 30,000 people expected to begin in July.
The company has partnered with the US National Institute of Allergy and Infectious Diseases, one of the institutes of the National Institutes of Health, to develop the vaccine. Lonza, a Swiss biotech company, has signed a ten-year contract to develop and manufacture the Moderna vaccine, with the aim of producing one billion doses per year.
Unlike the Oxford vaccine, the Moderna candidate uses the messenger RNA (mRNA) technique for producing a vaccine. These new types of vaccine use a synthetic mRNA molecule to trick the body into developing the natural viral proteins that spread an infection. The immune system detects these proteins and triggers a defence response.
Scientists have claimed that mRNA vaccines are faster, safer and cheaper to produce than traditional vaccines, where a small amount of the inactivated virus is given to the patient in order to trigger an immune response. Use of mRNA in human vaccines is still new and relatively untested, with uncertainties remaining around the strength of the immune defence provided, and how much synthetic mRNA is needed.
The vaccine in development at Imperial College London also uses mRNA techniques.
What is the Government doing?
The Government announced an initial £20 million of research funding for a vaccine in February. The first projects to benefit from this funding were announced on 23 March. This included the Oxford vaccine. An additional £84 million of funding was announced on 17 May.
The Government launched the vaccines taskforce on 17 April. Kate Bingham, chair of the taskforce, has stated that:
Our immediate aim on vaccines is two-fold: to ensure everyone in the UK that needs to be vaccinated against Covid-19 can be as soon as practicable. Second, to ensure adequate global distribution of vaccines to bring the quickest possible end to the pandemic and the economic and social damage it causes.
The Government has announced £210 million of support for the Coalition for Epidemic Preparedness Innovations, the global coalition coordinating the international vaccine response to Covid-19.
The Joint Committee on Vaccination and Immunisation published interim guidance on priority groups for vaccination on 18 June. It advises that frontline health and social care workers and “those at increased risk from Covid-19 infection, stratified according to age and risk factors” should be prioritised once a vaccine is successfully manufactured.
On 14 July 2020, Baroness Sheehan (Liberal Democrat) is to ask the Government what plans it has “to ensure that a COVID-19 vaccine, if developed, is (1) available to, and (2) affordable for, low- and middle-income countries”.
- Norbert Pardi, Michael J Hogan, Frederick W Porter and Drew Weissman, ‘mRNA vaccines—a new era in vaccinology’, Nature Reviews Drug Discovery, 12 January 2018
- Parliamentary Office of Science and Technology, ‘Vaccines for Covid-19’, 22 April 2020
- Qasim Rafiq and Martina Micheletti, ‘Coronavirus vaccine search: how we’re preparing to make enough for the whole world’, The Conversation, 13 May 2020
Image by PixxlTeufel from Pixabay.