A 31-year-old woman in Spain caught Covid twice in 20 days, the shortest known difference between infections, scientists say.
Researchers in Spain have given details of a health worker who tested positive a few days before Christmas in December 2021 and again in January 2022. The case is further evidence that the Omicron variant can avoid immunity even from recent previous infections.
The woman, who had been fully vaccinated and had received a booster vaccine 12 days earlier, tested positive on a PCR screening test of staff on 20 December. She developed no symptoms and isolated herself for 10 days before returning to work.
On January 10, 2022, just 20 days after the first positive test, she developed a cough, fever, and generally felt unwell and underwent another PCR test. That was also a positive.
Sequencing of the entire genome showed that the patient was infected with two different variants of Covid. Her first infection was with the Delta variant, and the second was with the Omicron variant, which is known to be more infectious and can avoid immunity from past infections and vaccinations.
Dr Gemma Resio of the Institut Català de la Salut in Tarragona and one of the study’s authors said: “This case highlights the potential of the Omicron variant to avoid previous immunity from either natural infection with other variants or vaccines. ”
She added that the case emphasizes the importance of genomic observation. “Such monitoring will help identify options with the ability to partially evade the immune response,” she said.
Re-infections are registered in the United Kingdom, but require 90 days between positive tests. Official figures show that nearly 900,000 people in England were potentially infected twice with Covid by early April. However, the number is not accurate because only genome sequencing can determine whether infections are caused by different variants and not all infections are reported.
Paul Hunter, a professor of medicine at the University of East Anglia, said: “This case is not very surprising, although the difference between infections is very small. We have known for several months that there will be re-infections. The Omicron variant, with its escape mutations, made recurrences even more likely.
Now that Omicron is the dominant option, previous Omicron infection may make re-infection – especially so fast – less likely. Researchers have previously predicted that as Covid-19 enters an endemic phase, re-infections are likely to occur within three months to five years.
“We can expect new waves of infections, especially in the winter, even without new options,” Hunter said. “Fortunately, the evidence is that immunity to serious diseases is more stable than immunity to infections. So, although re-infections will continue to occur for many years, over time we will see fewer serious illnesses and deaths. “
Professor Lawrence Young, a virologist at the University of Warwick, said: “While it is difficult to extrapolate from a single case, this report highlights the ability of the Omicron variant and its sub-variants to re-infect even those who are fully vaccinated. “That explains the extremely high levels of infection we’ve experienced in the UK.”
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