Inhabitants of Swedish-Somali origin are at great risk for covid-19
In Editor’s choice of 19 March Fiona Godlee writes, “With the covid-19 pandemic we have entered extraordinary times, when some things are known but many more are not and where decisions must be made nonetheless.” We fully agree.
Among the first 15 deaths due to covid-19 in Stockholm County, six were reported, by the Swedish-Somali medical society, to be of Somali origin (March 24). Considering that only 0.84% of the Stockholm County population was born in Somalia (n=8,178 by December 2019) this is an astonishing high rate.
Socio-economic factors, e.g. cramped housing accommodation, high rates of smoking and poor understanding of the Swedish language (which in turn leads to poor understanding of health information on covid-19 provided by the authorities) may explain the situation. Another possible explanation is Ethnic benign neutropenia - the most common form of neutropenia worldwide and very common among East African populations.
A risk factor that we want to highlight, however, is the low vitamin D levels found in the Swedish-Somali population. Vitamin D status is strongly related to low sun exposure and dark skin. In two different studies, the great majority of Swedish women of Somali origin had very low levels of S-25(OH)-D (< 25 nmol/l).[3,4] In Finland, Somali women required more than twice the amount of vitamin D in order to maintain recommended vitamin D status.  In addition, vitamin D deficiency was twice as common, regardless of gender, in immigrants from Africa compared with those from the Middle East.
There is evidence that vitamin D is involved in our defence against respiratory tract infections. According to a meta-analysis, vitamin D supplementation (daily-weekly dosage) prevents acute respiratory tract infections, especially in those with 25(OH)-D below 25 nmol/l (NNT = 4). In a randomised trial on individuals with frequent respiratory tract infections, treatment with cholecalciferol 4000 IE/day reduced the need for antibiotic treatment. The mechanism is debated; however, modulation of the renin-angiotensin system has been implicated in animal studies of acute respiratory distress syndrome, and angiotensin-converting enzyme 2 is a well-established receptor for the SARS-CoV virus.
In order to cope with the covid-19 epidemic, preventive measures could be administration of vitamin D to high-risk populations, e.g. dark-skinned adults with low sun-exposure and/or individuals with risk factors for respiratory tract infections. Although it may not always be helpful, it is unlikely to be harmful.
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Competing interests: No competing interests