Promise and challenges in the development of COVID-19 vaccines.

The pandemic outbreak of COVID-19, caused by coronavirus SARS-CoV-2, created an unprecedented challenge to global public health system and biomedical community. Vaccination is an effective way to prevent viral infection, stop its transmission, and develop herd immunity. Rapid progress and advances have been made to date in the development of COVID-19 vaccines. Currently, more than 115 vaccine candidates have been developed from different technology platforms with several of them in clinical trials. Most of those vaccine candidates are developed based on the experience with other coronaviruses with an aim to induce neutralizing antibodies against the viral spike protein or its different receptor binding domains. Here, we discuss the promise, potential scientific challenges, and future directions for the development of a safe and effective COVID-19 vaccine. We also emphasize the importance of a better understanding of the infection pathogenesis and host defense mechanisms against SARS-CoV-2 infection.