The immune changes in COVID-19 across different severity groups is very complex. A group of scientists led by Prof Kenneth Smith, and including Dr Hélène Ruffieux and Prof Sylvia Richardson at the MRC Biostatistics Unit, have carried out new research into how the immune system is affected in different ways for those who have contracted COVID-19.

Using detailed clinical and immune phenotyping datasets, extracted from blood samples collected in 207 patients with COVID-19 during the first peak of the pandemic, the scientists analysed infected individuals with a range of disease severities over 12 weeks from symptom onset.

The new research, published in Immunity, finds that an early robust bystander CD8 T cell immune response, without systemic inflammation, is characteristic of asymptomatic or mild disease. Patients presented to hospital had delayed bystander responses and systemic inflammation already evident near symptom onset. Such early evidence of inflammation suggests immunopathology may be inevitable in some individuals, or that preventative intervention might be needed very early in the disease course. Viral load does not correlate with the development of this pathological response, but does with its subsequent severity.

Dr Hélène Ruffieux, one of the scientists involved in this new work, says:

The clinical and cellular data collected in Cambridge from COVID-19 patients and healthcare workers constitute a very rich basis for studying the immune cell dynamics. Using longitudinal and latent factor modelling, our team could gain new insight into the different types of immune responses to infection, and their relation to clinical severity and recovery.

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