A 31-year-old woman, vaccinated with booster against Covid, tested positive for the Omicron variant of Sars-CoV-2 just 20 days after getting Delta infection. For the researchers who described the case in Spain, this is the shortest interval known so far between two Covid infections. The protagonist of the double record contagion is a health worker. The woman, according to a note from the European Congress of Clinical Microbiology and Infectious Diseases (Eccmid 2022, scheduled in Lisbon in Portugal from 23 to 26 April), during which the case is presented, has contracted Covid-19 twice in 3 weeks. She first tested positive on December 20, 2021, in a PCR test (the classic molecular swab) during the screening of personnel in the workplace. She had received the booster 12 days earlier and did not develop any symptoms. She isolated herself for 10 days before returning to work. And on January 10, 2022, just 20 days after testing positive for the first time, she developed a cough, fever, general malaise. You ran another PCR test. This was also positive. Whole viral genome sequencing revealed that the patient was infected with two different Sars-CoV-2 strains. The first infection, in December, was with the Delta variant. The second, in January, with the Omicron variant which had been classified as a variant of concern by the World Health Organization just over a month earlier, on November 26, 2021.Omicron has quickly become the dominant variant worldwide, is much more contagious than Delta and can evade immunity from previous infections and vaccination, explain the experts who dealt with the case of ultra-rapid reinfection. A case that, underlines one of the authors of the study, Gemma Recio, of the Institut Català de Salut of Tarragona in Spain, “highlights the potential of the Omicron variant to circumvent the previous immunity acquired from a natural infection with other variants or from vaccines. “People who have had Covid – he continues – cannot assume that they are protected from reinfection, even if they have been fully vaccinated. However, both previous infection with other variants and vaccination appear to partially protect against serious illness and hospitalization “with Omicron. For Recio, close double contagion also shows” the need for genomic surveillance of viruses in infections affecting fully vaccinated people. and in cases of reinfection in cured people. This monitoring will help detect variants with the ability to partially evade the immune response. “