from delta to omicron variant in just 20 days

It is the shortest known interval for a coronavirus reinfection: 20 days. Spanish researchers have given details of the case of a 31-year-old health worker who was infected with COVID-19 twice in three weeks. The case report will be presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) which will be held from Saturday in Lisbon.

Certainties and unknowns about the omicron variant to start the year

Know more

The woman, a worker in the health sector, tested positive for the first time on December 20, 2021, in a PCR test carried out during the screening of personnel at her workplace, the ECCMID indicates in a press release.

In addition, she was fully vaccinated and had received a booster shot 12 days earlier. The patient, who did not develop any symptoms, self-isolated for ten days before returning to work. On January 10, 2022, just 20 days after first testing positive, she developed a cough, fever, and general malaise, for which she underwent another PCR test. This was also positive.

Whole genome sequencing showed that the patient had been infected by two different strains of SARS-CoV-2. Her first infection, in December, was with the delta variant. The second, in January, was with the omicron variant.

The omicron variant had been identified as a variant of concern by the World Health Organization just over a month earlier, on November 26, 2021. The strain, which has become the dominant variant worldwide, is much more infectious than the delta and can evade immunity from previous infections and from vaccination.

Dr. Gemma Recio, from the Institut Català de Salut in Tarragona, is one of the authors of the study: "This case highlights the potential of the omicron variant to evade previous acquired immunity, either by natural infection with other variants or by the vaccines”.

The vaccine protects against severe disease

“In other words, people who have had COVID-19 cannot take it for granted that they are protected against reinfection, even if they have been fully vaccinated. However, both previous infection with other variants and vaccination seem to partially protect against severe disease and hospitalization in people with omicron”, Recio points out.

In addition, this researcher stresses the need to carry out "genomic surveillance" of the viruses in infections in those who are fully vaccinated, as well as in reinfections. "This surveillance will help detect variants with the ability to partially evade the immune response."