HomeResourcesVaccines, mutations and data: Reporters, all your COVID-19 questions answered

Vaccines, mutations and data: Reporters, all your COVID-19 questions answered

These health reporters got an expert rundown of what the latest evidence has to say about the new coronavirus. Now you can watch it too.

Resource details:

Publication title: Evidence-informed health media reporting series: COVID-19 Explainer
Author(s): Cochrane South Africa and the South African Medical Research Council
Publication date: 18 September 2020

What the webinar is about:

This is the fourth edition of Cochrane South Africa’s evidence-informed health media reporting webinar series. This session covered a broad range of questions about COVID-19 submitted by members of Bhekisisa and Health-e News Service and was presented by Wolfgang Preiser. Preiser is a virologist and the head of Stellenbosch University’s medical virology division in the faculty of medicine and health sciences. His research interests include the diagnosis, treatment and epidemiology of viral infections such as HIV and the study of viral diseases that move from animals to humans such as COVID-19.  

Key take-aways from the webinar:

COVID-19 and vaccines

  • There is no vaccine available for any of human coronaviruses, including the 2003 Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and the 2012 Middle East Respiratory Syndrome Coronavirus (MERS-CoV). Vaccine efforts were initially underway for these coronaviruses but were abandoned due to a lack of sustained funding. The illness that earlier coronaviruses caused were first considered too mild to require vaccination. Additionally, SARS-CoV didn’t fully establish itself in the human population, while MERS-CoV was largely controlled by vaccinating camels — which prevented its transmission to humans.
  • If a vaccine is developed, scientists aren’t certain how long the immunity it provides will last. It may turn out that people will require regular shots. “It might not be just a question of one or two doses and you’re done for life,” Preiser explains. 
  • There is a strange phenomenon to be cautious of – Antibody Dependent Enhancement (ADE). How does that work? “By vaccinating somebody you may make infection with related but not identical viruses worse,” Preiser says. This has been seen with the dengvaxia vaccine for dengue fever. 
  • It’s a long road from vaccine trials to the shots being licensed, and then finally producing enough doses to go around, Preiser says. He explains: “It will still be a challenge to go into large scale production of a new vaccine in such a short period of time”.

Why do some people get more sick than others? 

  • There are some known risk factors for severe COVID-19 disease. 
  • Age and certain underlying conditions such as diabetes, obesity and hypertension are risk factors for severe COVID-19 disease. HIV and TB are risk factors too, but the degree of risk isn’t as high as was initially feared. 
  • It’s speculated that the amount of virus you’re exposed to when you first get infected — called the inoculum — could also affect how sick you get. But the evidence for this is weak, Preiser says. For example, if somebody with COVID-19 coughs in your face and neither party is wearing a mask, you will be exposed to a lot of SARS-CoV-2 particles, so the virus will replicate faster, Preiser explains. As a result, your immune system may not be able to mount an effective response in time. Wearing masks may reduce the amount of virus to which people are exposed and prevent severe illness, but the evidence for this remains scant, he says. 
  • What about genetic and hereditary factors such as blood groups? “The verdict is still out”. A thorough more systematic look at the available evidence would be required to draw conclusions here. 

Coronavirus mutations 

SARS coronaviruses replicate and mutate relatively slowly when compared to other viruses such HIV, which replicates at a high rate. Because HIV can adapt so quickly, there could be many strains of the virus, and it could potentially become drug-resistant. “[coronaviruses replicate at] a fraction of what you see with HIV,” Preiser explains.

COVID-19 data

  • When looking at COVID-19 death rates and infection tallies from different countries, it’s important to remember that the numbers will differ depending on different nations’ rules about which people qualify for a test and which type of test is used. For example, people older than 55 and healthcare workers being prioritised for testing in South Africa’s City of Cape Town earlier this year. [Note: testing criteria were expanded on October 8 to include “anyone in the Cape Metro and in the rural regions of the province, who is symptomatic”.] 
  • By restricting testing to people who are high risk — or symptomatic people for example — we get partially blind results. Countries’ testing policies may change over time too, Preiser says. Testing policies may change over time too.
  • These factors make this type of data complicated to work with and compare. 

Watch a recording of the webinar here.

[Please note: Information on the new coronavirus is rapidly changing. Please refer to Cochrane South Africa and the South African Medical Research Council’s websites for the latest information. Visit for updates on South Africa’s coronavirus response.]