A 31-year-old woman in Spain caught the Omicron infection just 20 days after the Delta variant, in what is claimed to be the shortest known gap between infections, according to researchers.
However, in a similar case, a rare breakthrough infection was reported in a vaccinated 61-year-old Delhi doctor in 2021, who contracted the Alpha and Delta variants within 19 days.
The Spanish woman, who was a healthcare worker, first tested positive for the infection on December 20, 2021, in a PCR test during staff screening at her place of work.
She was fully vaccinated and had received a booster shot 12 days earlier.
The patient, who didn’t develop any symptoms, self-isolated for 10 days before returning to work.
On January 10, 2022, just 20 days after first testing positive, she developed a cough, and fever and felt generally unwell, and had undergone another PCR test which was also positive.
Whole-genome sequencing showed that the patient had been infected by two different strains of SARS-CoV-2 — in December it was the Delta variant, and the second in January was the Omicron 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 Gemma Recio, of Institut Catala de Salut, Tarragona, Spain.
In other words, people who have had Covid-19 cannot assume they are protected against reinfection, even if they have been fully vaccinated, Recio added.
However, she said together the previous infection and vaccination partially protect the patient against severe disease and hospitalisation.
“This case also underscores the need to carry out genomic surveillance of viruses in infections in those who are fully vaccinated and in reinfections. Such monitoring will help detect variants with the ability to partially evade the immune response,” Recio noted.
The case report will be presented at this year’s European Congress of Clinical Microbiology and Infectious Diseases to be held in Lisbon, Portugal, from April 23-26.
A Delhi doctor, Veena Aggarwal was thrice infected with Covid-19 — contracting both the Alpha and Delta variants after vaccination.
Aggarwal first tested positive on August 16, 2020, and was asymptomatic. She received her first dose of the Covishield vaccine on February 1, 2021, followed by the second dose on March 15, 2021.
On April 12, she tested positive for the second time and had symptoms such as acute abdominal pain, fever, myalgia, and fatigue. Within 19 days, on May 3, she tested positive for the third time.
The infection resulted in hypoxia, hospitalization, and illness lasting seven weeks. Whole-genome sequencing showed the second infection was caused by the Alpha variant and the third by the Delta variant.
Her case reported in the peer-reviewed medical journal Frontiers in Medicine identified a rare breakthrough infection in 19 days and also confirmed it as reinfection, presenting the first such documented case of two reinfections and two breakthrough infections.