Recent studies have reported protective efficacy of both natural immunity and vaccine-induced immunity against SARS-CoV-2 challenge in Rhesus macaques. However, the importance of humoral and cellular immunity for protection against SARS-CoV-2 infection remains to be determined. In this article, the authors show that adoptive transfer of purified IgG from convalescent macaques protects naïve recipient Rhesus macaques against SARS-CoV-2 challenge in a dose dependent fashion. Depletion of CD8+ T cells in convalescent animals partially abrogated the protective efficacy of natural immunity against SARS-CoV-2 re-challenge, suggesting the importance of cellular immunity in the context of waning or subprotective antibody titres. These data demonstrate that relatively low antibody titres are sufficient for protection against SARS-CoV-2 in Rhesus macaques, and that cellular immune responses may also contribute to protection if antibody responses are suboptimal. They also show that higher antibody titres are required for therapy of SARS-CoV-2 infection in macaques. The authors concluded that these findings have important implications for the development of SARS-CoV-2 vaccines and immune-based therapeutics.