[COVID-19 - The vaccine miracle must include strictness and caution]

Outside of SARS-CoV-2 vaccines, there is little positive outlook for the control of Covid-19 epidemic. Schematically, two antagonistic and extreme strategies have been proposed, zero-covid and herd immunity. Between the two, often oscillating measures, based on medical but also societal and political considerations, have been taken without any major effect on the course of the epidemic. Vaccines are a game-changer by providing a real opportunity to sustainably protect everyone against infection and eliminate the circulation of the virus. The Pfizer, Moderna and AstraZeneca vaccines, the three currently authorized in France, overall induce remarkable protection rates of 95 %, 94 % and 70 % respectively. The surprise came from that this efficacy was obtained after a rapid development, by targeting only the viral protein S as antigen, and by using the administration of expression vectors innovative in vaccinology, consisting of either messenger RNA or recombinant adenovirus. However, bringing the epidemic under control requires a well-organized mass vaccination campaign. It also requires careful monitoring of many parameters such as the occurrence of adverse events, duration of induced immunity, vaccine efficacy against emerging variants of SARS-CoV-2, interest or not of vaccinating people already infected, vaccination of immunocompromised patients. Vaccination must be accompanied by the maintenance of barrier measures and gestures and an amplification of clinical and biological investigations both to validate its effectiveness on the Covid-19 epidemic and to prepare for future developments in vaccinology.