Fully Vaccinated Woman Infected With Omicron Just 21 Days After Delta Infection

THURSDAY, April 21, 2022 (HealthDay News) -- A fully vaccinated health care worker got COVID-19 twice in less than a month — the shortest known time between infections, Spanish researchers report.

The 31-year-old was infected with the Omicron variant just 21 days after catching the Delta variant.

"This case highlights the potential of the Omicron variant to evade the previous immunity acquired either from a natural infection with other variants or from vaccines," said study author Gemma Recio, a researcher at Catalan Institute of Health in Tarragona, Spain.

The woman first tested positive for COVID-19 on Dec. 20, 2021, during a staff screening at her workplace. She had received a booster shot 12 days earlier. She self-isolated for 10 days before returning to work and did not develop any symptoms.

But on Jan. 10, 2022, she developed a cough, fever and felt unwell in general. She went for another PCR test, and it, too, was positive.

Whole genome sequencing showed that the first infection was caused by the Delta variant and the second by Omicron, according to a case study presented Wednesday at a meeting of the European Congress of Clinical Microbiology & Infectious Diseases in Lisbon, Portugal. Research presented at meetings is typically considered preliminary until published in a peer-reviewed journal.

"People who have had COVID-19 cannot assume they are protected against reinfection, even if they have been fully vaccinated," Recio said in a meeting news release.

"Nevertheless, both previous infection with other variants and vaccination do seem to partially protect against severe disease and hospitalization in those with Omicron," she noted.

Recio said the case also underscores the need for genomic surveillance of viruses in infections and reinfections of fully vaccinated patients.

"Such monitoring will help detect variants with the ability to partially evade the immune response," Recio said.

The World Health Organization flagged Omicron as a variant of concern on Nov. 26, 2021, and it has since become the dominant variant worldwide.

Omicron is much more infectious than Delta and, as this case study shows, can evade immunity from past infections and vaccination.

More information

For more on Omicron, visit the U.S. Centers for Disease Control and Prevention.

SOURCE: European Congress of Clinical Microbiology & Infectious Diseases, news release, April 20, 2022