The time of the day could be an important factor in the risk of getting an infection, according to researchers in the US.
They showed how a protein in the immune system was affected by changes in the chemistry of the body through the day.
The findings, published in the journal Immunity, showed the time of an infection changed its severity.
An expert said drugs were likely to take advantage of the body clock in the near future.
Read More: Body clock ‘alters’ immune system