Sars-CoV-2 is a coronavirus with a lipid envelope, studded with various proteins, including the spike (S) glycoprotein (1,2). This glycoprotein has an essential role in the virus's ability to enter cells (1-3). As of early 2021, the immune response elicited during Sars-CoV-2 infection is partially understood. The spike glycoprotein is considered an important antigenic determinant, capable of inducing humoral immunity, including the production of neutralising antibodies, i.e. antibodies that prevent the virus from binding to and therefore entering cells (1,2). The spike glycoprotein also triggers a cellular immune response by activating T cells (1,2). As of early 2021, the vaccines developed against Sars-CoV-2 have mainly been designed to trigger an immune response to the spike glycoprotein (2). Many vaccines to prevent covid-19 have been under development in various countries since this epidemic began, including messenger ribonucleic acid (mRNA) vaccines, viral vector vaccines, inactivated or attenuated Sars-CoV-2 vaccines, and protein-based vaccines (containing Sars-CoV-2 purified proteins) (1,2,4). Some types of vaccine have already been in human use for a long time, such as live attenuated vaccines, used to prevent measles for example. Others are more recent, such as viral vector vaccines, used against Ebola virus disease for example (2,5,6).
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