This study is about testing a new cancer treatment called **BNT113** with another drug called **pembrolizumab**. It's for people with a certain type of head and neck cancer that has a virus called **HPV16** and shows a protein called **PD-L1**. The trial has two parts: Part A checks if BNT113 is safe to use with pembrolizumab. Part B compares the effects of using both drugs together versus just pembrolizumab alone. - **Length**: Treatment lasts up to 24 months. - **Visits**: Regular follow-ups are necessary. - **Risks**: Some medical conditions and previous treatments may exclude participation. The study is for patients without prior systemic therapy for this cancer type, and they must provide a sample of their tumor. If you have a different type of cancer or have taken certain treatments, you might not qualify. Participants will help researchers understand if the new combination is better than the existing treatment.