Vaccines and social distancing as weapons to fight COVID-19 in South Africa

In 2020 researchers used mathematical models to estimate just how effective vaccines and social distancing regulations needed to be to have fully stopped the spread of COVID-19 in its first few months in South Africa

Within 3 months of the pandemic, people were already tired of social distancing and other hard lockdown regulations, even though these were helping to stop the spread of the disease. 

They were instead putting their hopes on vaccines. They hoped that if enough people were vaccinated, pandemic-related restrictions could be lifted so that they could continue their lives as usual. Experts were however unsure just how many people had to be vaccinated for this effort to be of any real value.

A team of researchers from Zimbabwe, the UK and South Africa did these calculations. They first needed to understand how severe the disease was in South Africa, and how and when it was transmitted. Then only could they test how effective current efforts against the spread of COVID-19 in South Africa were in the early stages of the pandemic. They also worked out how effective vaccines might have been to stop it then, and in future. 

The research team adapted an existing mathematical model that takes account of the symptoms that someone with COVID-19 would experience. 

The model provided them with possible scenarios about how quickly the virus could reproduce and spread throughout South Africa. They used it along with data from the South African Department of Health to calculate how well social distancing worked in the first few months of the pandemic to stop the spread of COVID-19. 

They then simulated how many people needed to have vaccinations of different strengths for a national vaccine programme to have an impact.

The researchers calculated that COVID-19 had gained enough momentum during the first few weeks of the pandemic in South Africa to rapidly spread to various provinces.

Social distancing regulations on their own during the first few weeks of lockdown helped to reduce COVID-19 infections by at least 80%.

A vaccine that is only 70% effective at protecting someone from contracting the virus could have halted the spread of COVID-19 if at least 94% of South Africans got it. In the case of a vaccine with a 100% success rate, only 66% of South Africans needed to get it. 

The chances of so many South Africans getting vaccinated is always slim. Therefore, the researchers recommended that a vaccine that is as effective as possible must be used in South Africa to help prevent the spread of COVID-19.

Thanks to the research team’s efforts, much needed information from an African perspective was made available as part of the global effort to understand and handle the pandemic.

It confirmed studies from other countries, including China, that showed that in the absence of vaccines methods such as social distancing, quarantining and isolation could have a marked effect on reducing the number of COVID-19 cases being reported.

The researchers caution however that it is unsure if the data used reflect the true number of COVID-19 cases in South Africa. Also, the mathematical model used was only a simple one, and can only provide a rough idea about how COVID-19 spread.

At the time of the study, a potential vaccine that worked reasonably well was still months away from being successfully developed. The researchers noted that once it does become available, lots of logistics and planning would be needed to ensure that enough people receive it.  

Importantly, the study showed that a vaccine with a success rate of between 70% and 100%, along with social distancing measures, can be used together to stop the spread of COVID-19 in South Africa. Having successful vaccines available could therefore support South Africa’s control programmes.

Abstract

The emergence and fast global spread of COVID-19 has presented one of the greatest public health challenges in modern times with no proven cure or vaccine. Africa is still early in this epidemic, therefore the extent of disease severity is not yet clear. We used a mathematical model to fit to the observed cases of COVID-19 in South Africa to estimate the basic reproductive number and critical vaccination coverage to control the disease for different hypothetical vaccine efficacy scenarios. We also estimated the percentage reduction in effective contacts due to the social distancing measures implemented. Early model estimates show that COVID-19 outbreak in South Africa had a basic reproductive number of 2.95 (95% credible interval [CrI] 2.83–3.33). A vaccine with 70% efficacy had the capacity to contain COVID-19 outbreak but at very higher vaccination coverage 94.44% (95% Crl 92.44–99.92%) with a vaccine of 100% efficacy requiring 66.10% (95% Crl 64.72–69.95%) coverage. Social distancing measures put in place have so far reduced the number of social contacts by 80.31% (95% Crl 79.76–80.85%). These findings suggest that a highly efficacious vaccine would have been required to contain COVID-19 in South Africa. Therefore, the current social distancing measures to reduce contacts will remain key in controlling the infection in the absence of vaccines and other therapeutics.

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