According to Spanish experts, a 31-year-old healthcare worker contracted Covid twice in the span of 20 days, the shortest documented gap between infections.
The woman was infected with two separate strains, Delta in late December and Omicron in January.
According to the researchers, this suggests that even if you have had Covid before, you can get it again even if you have been fully vaccinated. In the United Kingdom, reinfections must wait 90 days between positive tests.
Using that criterion, health officials estimate that over 900,000 people have been infected twice with Covid since the beginning of April. Only whole-genome sequencing can confirm that different strains cause infections, and only a small percentage of positive tests go through this process.
The Spaniard had no symptoms after her initial positive PCR test, but she got a cough and fever less than three weeks later, prompting her to take another test. The tests revealed that two different coronavirus strains had infected the patient.