The COVID-19 pandemic has had a major impact across the world over the last 2 years. In the UK, patients of South Asian origin have higher mortality from COVID-19 than most other ethnic groups, of which patients of white ethnic origin are lowest. This, even after adjusting for underlying health conditions. The coronavirus responsible mainly infects the lining of the mouth, nose, throat and lungs, leading to potentially severe respiratory infections. These sites have their own community of fungi, bacteria and viruses (microbiome) which helps to protect against infections. The role of immunity at these sites (mucosal immunity) or of previous oral disease in COVID resistance, susceptibility or severity is currently unknown.

Early in COVID-19 infection, there are extremely high amounts of COVID virus in the saliva and mouth. Accompanying this, are high levels of different factors involved in immune responses – some of which protect against the infection, whilst some damage the mouth and lungs. The microbiome in the mouth had been closely linked to respiratory disease in general, and upsetting the normal, healthy balance of different microbes in these communities is possibly a factor in how severe the disease becomes, and what the long-term effects are.