Previous studies have found a link between low vitamin D levels and susceptibility to acute respiratory tract infections.
Dr Lee Smith, who took part in the new research at Anglia Ruskin University, said: “We found a significant crude relationship between average vitamin D levels and the number Covid-19 cases, and particularly Covid-19 mortality rates per head of population across the 20 European countries.
“Vitamin D has been shown to protect against acute respiratory infections, and older adults – the group most deficient in vitamin D – are also the ones most seriously affected by Covid-19.
“A previous study found that 75 per cent of people in institutions, such as hospitals and care homes, were severely deficient in vitamin D.”
Public Health England (PHE) standing advice is for people to consider taking vitamin D supplements during the autumn and winter months, when many are deficient.
Last month, PHE advised people to continue taking the supplements into the summer to avoid Vitamin D deficiency as a result of poor sun exposure due to the lockdown.
As of Thursday, Italy had recorded 29,684 deaths and Spain 25,857, according to data from Johns Hopkins University. However, both figures are likely to be a significant understatement of the true toll.
The new study, which had the participation of the NHS, is published in Ageing Clinical and Experimental Research.