The COVID-19 pandemic has created significant barriers to the treatment of cancer patients requiring regular hospitalisation, as coronavirus infection significantly increases the risk of serious and even fatal complications. In our case report, a middle-aged patient with advanced melanoma has developed immune-mediated pancreatitis after more than a year of pembrolizumab treatment. After changing the therapy, the patient was diagnosed with coronavirus infection, which led to nearly a month of hospitalisation and rehabilitation, thus suspending active oncotherapeutical treatment. Thanks to professional medical care, our patient successfully recovered from the severe COVID-19 pneumonia caused by the infection, even in the absence of a coronavirus vaccine. After recovery, he received two Pfizer- BioNTech vaccines in August and September 2021, and a follow-up CT scan showed almost complete remission. Given the patient's lack of complaints and the absence of tumours other than two residual pulmonary nodules, he was observed afterwards. Our patient was in a serious condition before the vaccines were introduced, but has recovered thanks to professional medical care.