The higher prevalence of common cold viruses in Africa may have helped the continent experience relatively lower death rates from Covid-19, a study of people in Zimbabwe suggests.
Many people in Africa may have built up antibodies that protected them from Covid-19 before the pandemic hit by coming into regular contact with other coronaviruses such as those that cause the common cold, researchers say.
Africa accounts for more than one third of global deaths from respiratory infections, suggesting coronaviruses and other pathogens circulate at higher levels there compared to the rest of the world.
The study suggests pre-existing cross immunity from the antibodies – which can last for one year or longer – may partly explain why Africa’s Covid-19 death toll has been lower than expected.
However, more studies are needed to determine the antibodies’ effects on Covid-19 infections, illness and deaths in African populations, the team says.
Despite Covid-19 infection rates in Africa being very high, the number of deaths has been comparatively low. Possible explanations include the continent’s lifestyle and climate, and its relatively youthful population.
A team led by researchers from the University of Edinburgh investigated another possible reason – whether antibodies produced in response to exposure to the six other types of common coronaviruses that infect humans react with the Covid-19 virus.
In 339 pre-pandemic blood samples collected between 2000 and 2019 from people in Zimbabwe – where flu and pneumonia cause almost one in 10 deaths – the team detected antibodies against Covid-19 in 32 per cent of the population.
Detailed molecular and computational analysis of the antibodies’ targets indicates many were produced by immune responses to infection with one of the six other types of coronavirus, including common cold viruses. Some also appeared to have been produced to fight other pathogens, included flu viruses and parasites that cause malaria and sleeping sickness.
The antibodies detected included those targeting parts of the Covid-19 virus – for example, the spike protein – used in some vaccines to induce protective immunity.
Some studies in Europe have found Covid-19 antibodies in blood samples taken before the first cases were detected. However, these cases have been attributed to early, undetected spread of the virus before the pandemic was declared. This is not the case in Zimbabwe because the team identified antibodies in archived samples collected from as early as 2000.
The study, published in The Lancet Microbe journal, was supported by the Scottish Funding Council and National Institute for Health Research (NIHR). It also involved researchers from the University of Zimbabwe, the Tackling Infections to Benefit Africa (TIBA) partnership and biotechnology company, PEPperPRINT.
Professor Francisca Mutapi, of the University of Edinburgh’s School of Biological Sciences, who led the study, said: “The world has a lot to learn from researching reasons underlying the way the pandemic unfolded in Africa. Only through studies such as this one can we derive actionable knowledge to better prepare for the next pandemic.”