SARS-CoV-2 vaccine development: where are we?

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has proved to be one of the most challenging infectious diseases in the modern era, and despite several countermeasures to lessen its impact, the spread of the virus is still affecting most countries. This renders the goal of active immunization of the population through vaccination a worldwide public health priority. In fact, only when efficient vaccination programs will be successfully implemented, a return to pre-pandemic normality can be considered. The scientific community has made a tremendous effort to blow the lid off the pathogenesis of the disease, and unprecedented efforts are ongoing with governments, private organizations, and academics working together to expeditiously develop safe and efficacious vaccines. Previous research efforts in the development of vaccines for other coronaviruses (Severe Acute Respiratory Syndrome Coronavirus 1 and Middle East Respiratory Syndrome Coronavirus) as well other emerging viruses have opened the door for exploiting several strategies to design a new vaccine against the pandemic virus. Indeed, in a few months, a stunning number of vaccines have been proposed, and almost 50 putative vaccine candidates have entered clinical trials. The different vaccine candidates use different vaccine development platforms, from inactivated whole virus vaccine to subunit vaccine, nucleic acid, and vectored vaccines. In this review, we describe strengths, flaws, and potential pitfalls of each approach to understand their chances of success.