  In this paper, we propose a blockchain-based cold chain technology for
vaccine cooling track. The COVID-19 pandemic has caused the death of millions
of people. An important step towards ending the pandemic is vaccination.
Vaccines must be kept under control temperature during the whole process, from
fabrication to the hands of the health professionals who will immunize the
population. However, there are numerous reports of vaccine loss due to
temperature variations, and, currently, people getting vaccinated have no
control if their vaccine was kept safe. Blockchain is a technology solution
that can provide public and verifiable records. We review the World Health
Organization (WHO) cool chain and Blockchain technology. Moreover, we describe
current IoT temperature monitoring devices and propose Blockcoldchain to track
vaccine cold chain using blockchain, thus proving an unalterable vaccine
temperature history. Our experimental results using smart contracts demonstrate
the system's feasibility.
