An Overview of the COVID-19 Vaccines Following the publication of the genetic sequence of the severe acute respiratory syndrome virus 2 (SARS-CoV-2) virus in January 2020, pharmaceutical companies worldwide have been racing to develop a safe and effective vaccine, with many reaching clinical trials in record time. Image Credit: Viacheslav Lopatin / Shutterstock.com The method of action and constituents of any particular vaccine may vary wildly, just as the viruses they protect against target different cells and take different routes to infection. SARS-CoV-2 has been well reported to induce a range of immune responses in patients, with some remaining non-symptomatic while others just as heavily infected require hospitalization. This variability makes the development of a long-lasting vaccine that will guarantee immunity throughout the whole population highly challenging.