The current COVID-19 vaccine trials in South Africa revealed that far more people are infected but asymptomatic than previously thought.
This is feedback from Professor Shabir Mahdi from the University of Witwatersrand, who is leading South Africa’s first COVID-19 vaccine trial.
Speaking to CNBC Africa, Mahdi said they faced an unexpected challenge because of the rapid rate at which the COVID-19 virus is spreading in areas where the trials are conducted.
Part of the enrollment process for the COVID-19 vaccine trial involves the screening of individuals to see if they are infected or have previously been infected with the virus.
To their surprise, the researchers identified a much higher-than-anticipated percentage of people who have been infected by the virus but who were asymptomatic.
He said between 50% and 66% of adults who are infected with COVID-19 are completely asymptomatic.
In children, this is even higher – around 80% of all children who are infected are asymptomatic.
“The majority of COVID-19 infections are going unnoticed,” Mahdi said, adding that only around 10% of all COVID-19 cases are officially reported.
He said they have now tailored their enrollment process to include stricter screening to ensure people who participate in the study did not have the virus.
This is needed to accurately assess the effectiveness of the vaccine which is aimed at people who have never had COVID-19.
COVID-19 vaccine trial in South Africa
Mahdi explained in an article that the study in South Africa is for a non-replicating vector base COVID-19 vaccine that was developed by the Jenner Institute at the University of Oxford.
Pre-clinical studies of this vaccine candidate have demonstrated initial evidence of its safety, as well as its ability to protect against COVID-19 disease.
Madhi reached out to the University of Oxford to include South Africa as part of the clinical development plan of the vaccine, and they agreed.
They are now busy with the enrollment process, and he highlighted that participation in the vaccine trial is completely voluntary.
“We’ve just reached the 200 mark out of the 2,000 participants that we plan to enrol. We expect to have completed enrollment of all the volunteers over the next three to four weeks,” he said.
After eligible participants are identified they are randomly allocated to one of two groups. Half will receive the vaccine, and the other half a control substance, which in this case, is a placebo.
This methodology allows the researchers to provide robust data in terms of the safety profile of the vaccine.
The control group also makes it possible to determine whether the vaccine actually does have any impact on protecting against COVID-19.
The next steps
After the enrollment process, the vaccine will be given to half of the participants and the researchers will then keep in touch with all of the participants at least every two weeks.
This is done to determine whether or not experiencing any signs or symptoms of COVID-19. If they are, they will be asked to come in to be investigated to determine whether they are infected or not.
The endgame of the study is twofold. One is to evaluate the safety of the vaccine, which is something that is ongoing almost on a daily basis.
The second part is to do an analysis to determine whether the vaccine actually does protect against COVID-19.
“Specifically, we will be testing if the vaccine efficacy is at least 60% – that is by being vaccinated your risk for developing COVID-19 will be reduced by at least 60% if not more,” he said.
Madhi said they will probably be able to provide an answer as to whether this vaccine works and protects against COVID-19 by the end of November this year.
In the worst-case scenario, it might take us a bit longer – probably into the second quarter of next year.
Madhi cautioned that the fact that they’re embarking on a clinical trial doesn’t mean that they’re going to have a vaccine that’s going to protect against COVID-19.
Only about 10% of vaccines that go into clinical trials are eventually licensed for use.
“Right now there’ are approximately 200 vaccines that are being developed for COVID-19,” he said.
“It would be a huge accomplishment if, over the next 12 to 18 months, we are successful showing that even one out of every 20 of the vaccines that go into human studies are safe and provide some protection against COVID-19.”
He said at least for the next 12 months the only tools that we’ve got available to us to try to protect people is the non-pharmaceutical interventions which are widely publicised.