South Africa has not been left behind in the the race to find a vaccine for the virus that is holding the whole world hostage. In June 2020, South African medical researchers began vaccine trials for the Ox1Cov-19 vaccine, joining 75 other countries already involved in fast-tracked vaccine research.
The South African team is led by Shabir Madhi, Professor of Vaccinology at the University of the Witwatersrand, Johannesburg and Director of the South African Medical Research Council Vaccines and Infectious Diseases Analytics Research Unit. Their trial has a name – The Ox1Cov-19 Vaccine VIDA Trial.
Currently there is no cure for Covid-19, and the best we can do is simply to manage the outbreak by implementing lockdowns and non-pharmaceutical interventions like physical distancing and the wearing of facemasks. These practices have been enormously helpful, and have been credited with enabling most countries to bring down the potential number of Covid-19 cases, according to Madhi.
‘However,’ says Prof Madhi, ‘With the lifting of total lockdowns in a number of countries, including Spain, Italy, China (Beijing), South Korea and many states in North America, and due to non-adherence to non-pharmaceutical interventions, we have seen a recent upsurge in the number of Covid-19 cases.’
To manage outbreaks, Madhi explains that it is important to manage the virus’s effective reproductive rate, which means that, on average, every person who has Covid-19 should not infect any other person.
‘The effective reproductive rate for this particular virus is about 2.5, which means that in a population that is susceptible, on average, two to three people will be infected by every new case that is infected, and they will go on to infect another two to three people,’ explains Madhi.
To sustain low cases, the effective reproductive rate needs to be brought down to less than 1.
‘After South Africa went into lockdown in March, the number of Covid-19 cases waned, but the effective reproductive rate did not go under 1, and community transmissions were ongoing,’ says Madhi. ‘With the easing of lockdown, we had a rebound of cases, as expected. The magnitude of this will depend on how effective we are at abiding to and sustaining the non-pharmaceutical interventions.’
He compares the Covid-19 virus’s course to the course of the 1918 Spanish flu virus.
Spanish flu
‘With the Spanish flu, there were at least three to four waves of the outbreak before it became more of a seasonal virus. At that stage a large percentage of the population had already been infected, making transmission between people less efficient,’ says Madhi. ‘With the Spanish flu, the second wave was much more severe than the first wave, in part because the virus was mutating, which fortunately doesn’t seem to be the case with Covid-19.’
Not much is yet known about natural exposure to the Covid-19 virus. We don’t know, for instance, how long immunity lasts following a natural infection, the robustness of the immune responses, or the extent to which naturally induced immunity will actually protect a person against subsequent infections, especially those later in life.
The Ox1Cov-19 vaccine, developed and sponsored by the Jenner Institute at the University of Oxford, aims to create a more controlled and predictable manner of inducing a long-lasting immune response than might occur naturally.
How will the vaccine work?
The Ox1Cov-19 vaccine makes use of a new technology called viral vector vaccines. Viral vector vaccines use a weakened virus to help stimulate an immune response.
‘This type of technology has previously been used to design an Ebola vaccine, as well as experimental vaccines,’ says Madhi. ‘This vaccine makes use of a viral vector known as an adenovirus vector. Adenoviruses are very common in humans and usually cause a very mild illness. The adenovirus used in this particular vaccine doesn’t cause infection in humans and has been genetically engineered not to be able to replicate in the body, which would occur in the case of a live virus.
‘This particular non-replicating adenovirus contains spike proteins which are inserted into the adenovirus. The spike protein is found on the surface of the coronavirus, and is believed to be important in terms of the virulence of the organism to invade human cells. When this particular material is injected into your body, your immune system processes it and developes antibodies, so that when you are exposed to the natural virus, your body then has the antibodies to fight it off.’
Currently there are 178 Covid-19 vaccines under development, but Madhi says we would be extremely fortunate if even 5% of these are eventually licensed as vaccines.
Madhi’s team enrolled 2000 healthy individuals between 18 and 65 years of age to undergo the tests, including 50 individuals with HIV. The participants will be assessed fortnightly for 12 months to assess for respiratory illness and any other adverse events.
The vaccine, in development since March 2020, might be ready in early 2021.
‘If this is achieved, it will be a major milestone,’ says Madhi. ‘It will require fast tracking steps, with different evaluations being done concurrently. The unique circumstances do not permit business as usual.’
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