Vaccines are ultimately the only way to ensure that we beat COVID-19, yet vaccine hesitancy remains a threat to attaining herd immunity and protecting the whole community. In this series, Virologist at Rhodes 老虎机游戏_pt老虎机-平台*官网 and member of the Provincial COVID-19 Expert Panel, Professor Rosemary Dorrington, will address queries, fears, and misinformation that many of our citizens face.
Question: “What are all these different coronavirus variants I keep hearing about? And which ones are affecting South Africa?”
Prof responds:
The nature of viruses is that they mutate over time – they evolve. Most changes don’t make too much of an impact on the viral lifecycle, but sometimes a change will often affect the properties of the virus enough to cause concern. These affected properties could impact disease severity, virus transmissibility and potentially the performance of vaccines.
The coronavirus that causes COVID-19, called SARS-CoV-2, started showing mutations that posed an increased risk to global public health during late 2020, and this prompted characterisation of specific “Variants of Interest” (VOIs) and “Variants of Concern” (VOCs) so that they could be monitored accordingly.
To assist with public discussions of variants, the World Health Organization (WHO) convened a group of scientists from its Virus Evolution Working Group, who recommended using letters of the Greek Alphabet, such as Alpha, Beta, Gamma, and Delta, to make it easier and more practical for the variants to be discussed by non-scientific audiences.
Variants of Interest and Variants of Concern
Now that we understand what virus variants are and how the SARS-CoV-2 naming variants work, we can look at the difference between VOIs and VOCs.
A SARS-CoV-2 VOI is one that causes significant community transmission in multiple countries (WHO). The currently circulating VOIs are Eta, Iota, Kappa and Lambda. None of these variants have been detected in South Africa yet.
A SARS-CoV-2 VOC meets the definition of a VOI but is more dangerous as it also meets at least one of the following criteria:
- Increase in transmissibility or detrimental change in COVID-19 epidemiology;
- Increase in virulence or change in clinical disease presentation;
- Decrease in the effectiveness of public health and social measures or available diagnostics, vaccines, or therapeutics.
The current VOCs include Alpha, Beta, and Delta, all of which have been detected in South Africa.
The Alpha Variant
This variant was first detected in the United Kingdom in September 2020 and was classified as a VOC on 18 December 2020.
It has an increased transmissibility of between 43 to 90% and has been shown to increase the COVID-19-related death toll from 2.5 to 4.1 deaths per 1 000 detected cases.
Although this variant did make its way into South Africa in January 2021, a relatively low number of cases were detected.
The Beta Variant
This variant was first detected in South Africa in August 2020 and was classified as a VOC on 18 December 2020.
Compared to earlier versions, the Beta variant spreads faster from person to person and has an increased chance to evade some of the body’s natural defences from previous infection or vaccination. The AstraZeneca vaccine was rejected for use in South Africa in February 2021 after trials showed it was ineffective in preventing Beta variant infection.
Some data shows that the Beta variant can cause more severe cases of COVID-19 in people who have been hospitalised.
It was the dominant variant in South Africa from November 2020 until recently, when the Delta variant took over.
The Delta Variant
This variant was first detected in India in October 2020 and was classified as a VOC on 11 May 2021. This variant made its way to South Africa in May 2021 is currently the most dominant variant in South Africa.
People infected with the Delta variant produce up to 1000 x more virus in their nasal passages than the original SARS-CoV-2 virus, and therefore this variant can spread even faster from person to person than Beta, and it has an increased risk of severe disease and hospitalisation for those infected. The symptoms of this variant include a runny nose, sneezing, sore throat and headaches (sacoronavirus.co.za). And unlike other variants, Delta now readily infects and causes significant illness in younger people, including children 18 years and younger.
Of concern is data released in the past week by the US Centres for Disease Control that shows Delta can cause breakthrough infections in vaccinated people who are then infectious and can spread the virus to others. This said, it is really important to know that the vaccines are still more than 95% effective at preventing severe disease and hospitalisation. And in America, 99% of COVID-related deaths were amongst the unvaccinated population.
Additional sources:
https://www.nicd.ac.za/covid-19-update-new-variants-detected-in-south-africa/
https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/
