This analysis provides a clear answer to a simple question: what is the effect of co-infection with common viruses on top of Covid? We compared outcomes across people who tested positive for three different viruses (influenza (flu) virus, adenovirus, and RSV) and found that co-infection with the flu virus was associated a higher chance of critical illness and death. This has direct implications for the NHS, suggesting that we should test patients more often for flu. It also provides another reason to vaccinate people more widely against both flu and Covid, particularly as flu is expected to make a comeback in 2022. As with much of our work, this was discussed immediately at the UK government advisory group, SAGE, and has already influenced the thinking around policy.
