After the declaration of a public health emergency of international importance, hospitals have become a benchmark in the response to the pandemic. It is important to assess health professionals' response capacity to the COVID-19 pandemic at a referral hospital in Pernambuco, in northeastern Brazil. This study deals with qualitative evaluative research, of the case study type. Three methods were used to identify critical events: interviews with 18 healthcare professionals who had worked on the "front line" of care for people with COVID-19; direct observation in the sectors of this hospital; and literature review. The interviews were transcribed and analyzed using MaxQDA Analytics pro 2020® software, using the Actor-Network Theory for analysis; and to interpret the critical events the categories of resilience: absorption, adaptation and transformation. It was found that the response capacity of professionals was influenced by five critical events: the arrival of cases, new ways to connect the patients with their social support network, social and personal impact on the daily life of professionals, insufficient supplies, essential equipment and confirmatory tests, and shortage and illness of professionals. In everyday experiences, the response capacity of professionals has led to a process of priority adaptation, which can accelerate important changes in the health system.