Neutralising antibodies were first shown to be a correlate of protection from COVID-19 in early 2021, based the results of Phase III trials of 7 vaccines showing protection against the Wuhan strain. This correlate has been used both in the approval of new vaccines as well as the extension of current vaccines to younger age groups based on non-inferiority of antibody responses. More recently, neutralising antibody responses have also been shown to be predictive of protection against SARS-CoV-2 variants and against severe infection. However, a major question to establish whether antibodies are mechanistic in mediating protection from COVID-19? Here I will discuss evidence from a meta-analysis of trials using passive antibodies in the prevention and treatment of COVID-19. This work demonstrates that the administration of passive antibodies is able to achieve similar levels of protection at similar titres to vaccine-mediated responses. This provides strong evidence for neutralising antibodies as mechanistic mediators of protection from symptomatic and severe COVID-19.