If cases of reinfection with COVID at the beginning of the epidemic were rather rare, the picture has changed dramatically with the advent of the Omicron variant.
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Spanish researchers have found that a 31-year-old Spanish healthcare worker contracted COVID twice in 20 days, the shortest case ever documented again.
Tests showed the woman contracted two different types of COVID: via Delta at the end of December and Omicron in January.
According to the researchers, this example shows that a person infected with the COVID virus or who has been vaccinated is not necessarily immune, according to the BBC.
In the UK, authorities are asking for a 90-day period between two positive tests for re-infection.
Based on this definition, health officials say nearly 900,000 people are likely to be re-infected by April 2022.
The Spaniard showed no symptoms after her first positive test, but less than three weeks later she developed a cough and fever which prompted her to take another test.
When the tests were analyzed in more detail, they showed that the patient had contracted two different strains of coronavirus.
In a presentation to the European Conference on Clinical Microbiology and Infectious Diseases, study author Dr. Gemma Risio said the case showed that Omicron can “escape pre-acquired immunity either from natural infection with other variants, or from vaccines.”
In other words, people who have contracted Covid-19 cannot assume that they are protected from reinfection, even if they have been fully vaccinated.
“However, it appears that previous infection with other variants and vaccination partially protects against severe illness and hospitalization in people with omicrons,” the doctor added.
COVID infections increased sharply in December 2021 after the appearance of the most infectious variant of Omicron, also due to BA.2, which appeared in early March.
Before Omicron, 1% of all registered cases in the UK were classified as a second infection – but that number has now risen to 11%.
Most are likely to be people infected with alpha or delta variants and then re-infected with the more infectious omicron.
Scientists believe that everyone will eventually get COVID twice, and likely several times in their lifetime.
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