Transforming a vaccine concept into a real vaccine product is a complicated process and includes finding suitable antigens and regulatory, technical, and manufacturing obstacles. A relevant issue within this scope is the clinical trial process. Monitoring and ensuring the integrity of trial data using the traditional system is not always feasible. The search for a vaccine against the coronavirus SARS-CoV-2 illustrates this situation. The scientific credibility of findings from several vaccines' clinical trials contributed to distorted perceptions concerning the benefits and risks of the drug. This scenario is ideal for applying technologies such as Blockchain and Smart Contracts in healthcare issues. This paper proposes a protocol based on Smart Contracts, named VaccSC, to enable transparency, accounting, and confidentiality to Phase III of vaccine experiments. The protocol was implemented in Solidity language, and results show that the VaccSC enables double-blindness, randomization, and the auditability of clinical data, even in the presence of dishonest participants.