With the onset of the Covid-19 pandemic, vaccines have been successfully produced some 11 months after the virus was first detected - a process which would normally take up to a decade or two, writes Barry Schoub.
In December 2019, global health authorities were alerted to a cluster of unusual pneumonias in the city of Wuhan in central China.
A year later, 10 December 2020, the ensuing pandemic of the SARS CoV-2 coronavirus had claimed over one and a half million lives and caused illness in close on 70 million people worldwide, some of whom would suffer the debilitating long-term consequences of the illness - the so-called "long Covid".
In the absence of a vaccine or preventive drug, measures to curb the pandemic have relied on modifying and controlling human behaviour - what have been termed non-pharmaceutical interventions (NPI's). While these preventive measures were reasonably successful in China and other Asian countries, on the whole they be much less successful in Europe and North America.
Not since the devastating 1918/1919 Spanish influenza pandemic has the world been battered so severely by a rapidly spreading virus. Unsurprisingly, the public health focus has looked to developing vaccines, which have been so outstandingly effective in controlling many viral epidemics. Combining 21st century science with sophisticated modern technology, vaccines have been successfully produced some 11 months after the virus was first detected - a process which would normally take up to a decade or two to produce an effective vaccine.
Several potential vaccine candidates being investigated
As at 10 December 2020, 273 potential vaccine candidates are being investigated, the majority at the stage of laboratory and animal investigation. Clinical trials in human volunteers have been reached by 58 candidate vaccines, 11 of whom are in phase 3 trials, the final stage of clinical trial investigation, and one vaccine has been licensed for emergency usage in a few countries.
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As novel as the epidemic itself has been, so has vaccination posed unprecedented and unique challenges to public health planning. Most of the vaccines which have reached the final stages of development have employed constructs never before utilised for human vaccines.
The two most effective vaccines to date, have used the mRNA (messenger RNA) coding for the critical spike protein of the virus, to produce the requisite immunogenic protein in order to stimulate an immune response. Other front-runner vaccines have extracted the gene for the spike protein and spliced it into another harmless transporting virus, the adenovirus, to introduce it into the body.
The novelty of these vaccine designs, as well as the unprecedented speed at which these vaccines have been produced, have aroused since discomfort and anxiety about vaccine safety in the minds of a significant number of the general public.
Public health planners will undoubtedly need to address these not unreasonable fears, to avoid vaccine hesitancy growing to the point of threatening the necessary coverage levels needed to achieve herd immunity. Reassurance of the safety of these new vaccines comes from the independent control of the safety of the clinical trials and the rigour and depth of safety monitoring at all stages, from the clinical trials to licensure and post-licensure.
Questions about vaccine development
Many questions about Covid vaccines and their development still linger, despite the unprecedented scramble to pre-purchase vaccines by well-heeled, high-income countries.
Questions such as how durable is the immunity? (Three months down the line there does appear to be solid immunity, both antibody and cellular immunity.) Although remarkably effective in clinical trials, would this translate into similar level of efficacy in the field? While some vaccines did perform well in the small subsection of elderly volunteers, would this effectiveness be seen in the broader population of the elderly and also those with underlying illnesses who are more prone to serious disease?
This remains to be established. Importantly from a control point of view, would the vaccines be effective in stopping transmission of the virus, even if it does effectively prevent illness? Would the virus mutate to escape vaccine-induced immunity? Current knowledge of the virus would indicate that it is unlikely it would behave like the influenza virus.
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Most countries of the world, including South Africa, will need to approach population vaccination in stages.
Initially limited supplies of vaccines will go to priority groups such as frontline healthcare workers and the elderly in care homes.
At a later stage when more vaccines come through the pipeline, universal vaccination of the entire population will be the goal, in order to reach the magical threshold of herd immunity, to control the epidemic.
However, for the next few years at least, even with widespread availability of vaccines, control of the infection will still need to depend on the non-pharmaceutical interventions of masks, physical distancing and avoidance of indoor gatherings, to supplement the contribution of the vaccine.
Very few in the arena of vaccinology and public health will argue with the urgent need to develop and implement widespread vaccination of risk groups and the general population, in order to achieve herd immunity as soon as possible.
However, some concerns have been raised about the unprecedented scramble for vaccines by high income countries, despite the uncertainty of its long-term efficacy. Certainly, time will tell if the very promising results from the clinical trials will be successful in stamping out the pandemic.
However, few thoughtful people will disagree that the risk is worth taking, given the costs of not controlling the epidemic.
- Barry Schoub is chair of the Ministerial Advisory Committee on Covid Vaccines and Professor Emeritus of Virology at Wits.
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