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Covid update: What reduces risk of catching the virus? Antibodies, immune defenders & more

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Coronavirus is known to affect some more severely than others. This often comes down to a variety of factors including age and underlying health issues such as diabetes, high blood pressure and high cholesterol. Much confusion still lies as to why some countries have had less cases of death from COVID-19 than others. Could an immune defender be the reason to this?

The immune system’s memory of the new coronavirus lingers for at least six months in most people, it has been reported.

Although SARS-CoV-2 can be deadly, it has mild-mannered cousins called seasonal coronaviruses that are among the causes of the common cold.

Some scientists have suggested people might be shielded from SARS-CoV-2 infection if they have recently been infected by a seasonal coronavirus.

Researchers have found participants’ immune responses varied widely.

Persistent immune defenders were memory B cells, which jump-start antibody production when a pathogen is re-encountered, and two important classes of T cells.

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In a study published in MedRxiv, seasonal human coronavirus antibodies after an infection was further investigated. 

The team found all of the study participants had pre-pandemic antibodies that could recognise the seasonal coronavirus OC43.

One-quarter of participants also had antibodies that could recognize SARS-CoV-2, which probably developed in response to infection with a common-cold coronavirus.

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Scientists have found antibodies that recognize SARS-CoV-2 in the blood of people who have never caught the virus.

Children are particularly likely to harbour such antibodies, which might explain why most infected children have either mild illness or none at all.

Researchers from the Francis Crick Institute in London found that roughly 5 percent of 302 uninfected adult participants had antibodies that recognize SARS-CoV-2 while younger individuals aged between six and sixteen had 60 percent

It has been unclear whether previous infection with one of the ‘seasonal’ coronaviruses which cause the common cold wards off SARS-CoV-2 or its severe symptoms.

Why some countries are less affected by COVID-19 than others

One of the first large SARS-CoV-2 antibody studies in Africa suggests that by mid-2020, the virus had infected only four percent of people in Kenya.

Sophie Uyoga at the KEMRI-Wellcome Trust Research Programme in Kifili, Kenya, and her colleagues searched for such antibodies in samples of blood donated in Kenya between late April and mid-June.

Their research found that of those samples, the researchers estimate 4.3 percent of Kenya’s people had a history of SARS-CoV-2 infection.

The team’s estimate of antibody prevalence in Kenya is similar to an earlier estimate for the level in Spain.

However, Spain had more than 28,000 death cases by early July, whereas Kenya had lost 341 by the end of the same month.

The authors write the “sharp contrast” between Kenya’s antibody prevalence and its COVID-19 deaths hints that the coronavirus’s effects are dampened in Africa.

The reason for the lower death rates could include several factors, including age distribution, underlying chronic disease levels, and immune system priming, as to why the spread and severity of COVID-19 in much of Africa is different than that observed in Europe or the Americas, as reported in the study published in Science entitled COVID-19 in Africa: Dampening the storm.

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