ChAdOx1 nCoV-19 most likely means very little to you at present, but one day, hopefully in the not too distant future, it may have the ability to give you immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the agent that causes Covid19.
This vaccine, ChAdOx1 nCoV-19, is currently being developed by the University of Oxford, and their early stage results were published this month in The Lancet medical journal.
The preliminary report of the team’s combined Phase 1 and 2 trials of the vaccine showed that it was safe, caused minimal side effects and induced a strong immune response, with no serious adverse events noted. Phase 3 trials are due to start in Brazil soon.
Lead researcher, Andrew Pollard described the results as “encouraging” and said it was “a really important milestone on the path to the development of the vaccine.” However, Sarah Gilbert, another member of the team and professor of vaccinology at Oxford cautioned that there was still a long way to go before they could confirm that the vaccine would protect against developing COVID-19.
In a global pandemic that has infected more than 16 million people and claimed the lives of over 600,000, much of the world has pinned its hopes on a vaccine as a way out.
There are now more than 140 candidate vaccines tracked by the WHO as researchers around the world are racing to develop this eagerly anticipated vaccine. Notwithstanding the fact that they are attempting to do this within 12 to 18 months for a process that usually requires years of testing and additional time for large scale production.
Clinical trials that test new treatments are conducted in different phases that build on one another. In the pre-clinical stage of testing, researchers give the vaccine to animals to see if it triggers an immune response.
After this, there are Phase 1 clinical trials in which the vaccine is given to a small group of people to determine whether it is safe and to learn about the immune response it provokes.
In Phase 2, the vaccine is given to hundreds of people so scientists can learn more about its safety and correct dosage. In Phase 3, it is given to thousands of people to confirm its safety—including rare side effects—and effectiveness. These trials usually involve a control group which is given a placebo.
As of July 23, there were 142 vaccines in the preclinical testing stage, seventeen in Phase 1, thirteen in Phase 2, five in Phase 3 and none yet approved for general use.
In addition to the Oxford group, an American team is due to start their Phase 3 trials next week. This vaccine is being developed by the Vaccine Research Centre at the National Institutes of Health’s National Institute of Allergy and Infectious Diseases, in partnership with US biotechnology company Moderna.
Their initial results have also now been published this month in the New England Journal of Medicine and were promising as an immune response was demonstrated in those who received the vaccine. The most commonly reported side effects were fatigue, chills, headache, muscle pains and pain at the injection site.
Other teams who have carried out Phase 1 and 2 trials were Chinese researchers from institutes in both Wuhan and Beijing while the Murdoch Children’s Research Institute in Australia is conducting a phase 3 trial using a nearly 100-year-old tuberculosis vaccine. The vaccine is not thought to protect directly against COVID-19 but might boost the body’s non-specific immune response.
Which of these potential vaccines will eventually emerge as the most successful frontrunner is impossible to know until more clinical trial data become available.
After all, an ideal vaccine against SARS-CoV-2 would be able to confer immunity after one or two vaccinations; would protect target populations, such as those in older age groups and those with medical problems, including those with compromised immune systems; would offer protection for at least 6 months and reduce onward transmission of the virus to other contacts.
Of course, there are many hurdles to face—obtaining millions of dollars in funding, convincing regulators to approve human testing while demonstrating the vaccine’s safety and prove its effectiveness to the general population, many of whom are sceptical about the potential for mishaps in what may be perceived as a rushed job.
In addition to the concerns about safety given the accelerated pace of development, the anti-vaccination movement has gained traction in recent years.
Some people now reject vaccines outright (the “anti-vaxxers”) while others are “vaccine-hesitant.” This may be due to safety fears or mistrust of pharmaceutical companies and their motives, and many other “conspiracy theories,” despite no real or proven scientific basis.
The WHO currently lists vaccine hesitancy as a “Top 10 Threat to Global Health” where it shares a place alongside other health concerns such as antibiotic resistance, climate change and Ebola.
It is crucial to remember however, once the rules of good science apply, and are at the forefront of any potential vaccine, as well as a combination of safety and effectiveness, only then can it be expected to have a wide acceptance and uptake.
Most experts now feel a vaccine is likely to become widely available by mid-2021, about 12-18 months after COVID-19 first emerged. This in itself would be a remarkable scientific feat for which there is no precedent.