Covid-19's known unknowns.

Competing Interests: Competing interests: We have read and understood BMJ policy on declaration of interests and declare that all three authors have been wrong about covid-19. MM and MB initially believed substantial undocumented transmission meant that a large proportion of the UK population was infected during the first wave. Subsequent seroprevalence surveys indicated that this was not the case. GDS thought that SARS-CoV-2 would be amplified through children and substantial mortality displacement would be observed. Neither has been the case. Provenance and peer review: Commissioned; not externally peer reviewed.