One patient, three Covid-19 infections: An exception that’s becoming more common in Spain

“I don’t know of another case like mine,” says Bruno Polo, a young Spaniard who tested positive for Covid-19 in an antigen test taken before his planned Christmas Eve dinner. In October 2020 and in the summer of 2021, he also caught the coronavirus. “I must have the record for infections now,” he says. He doesn’t, but he is close. Last week, the Catalan health department reported a person who had been infected four times.

The case of the 21-year-old Polo may be the exception now, but it is likely to become increasingly common. Experts warn that reinfections will increase due to the fact that the antibodies lose effectiveness over time and that the omicron variant of the coronavirus partially evades the protection provided by Covid-19 vaccines.

Polo spent Christmas Eve alone at home, where he lives with his mother and older brother. He felt well, he didn’t have any symptoms and he ate a traditional Italian meal that his father had left by the door. In his head, he wondered if the test result was accurate, especially since the second line that indicated a positive case was only faint. To Polo, who was fully vaccinated and had recovered from two previous infections, it seemed like a bad joke.

His brother, a medical student, put him in contact with a doctor who confirmed the reliability of positive results from antigen tests. “The problem is the false negatives,” the doctor told him. In an antigen test, the brightness of the second line reflects the viral load of the test. In Polo’s case, the faint line indicated that he had a low viral load of the virus. To confirm the result, Polo tried to get a PCR test at a medical center the next day. But he was told that under Spain’s current protocol, these more accurate tests are limited to symptomatic cases in order to reduce the strain on the primary healthcare system. He tried to get tested at a private lab, but he says waiting in line would have taken hours. In the end, he gave up. “I had to accept the third positive and being confined to a room for seven days.”

During the self-isolation period, he occupied himself with books, video games and his studies, but he was still frustrated. This was not the first time he had missed out on festivities due to Covid-19. In October 2020, he tested positive a few days after coming into contact with a coronavirus case, although he had no symptoms. The fact that he was asymptomatic made him question whether Spain is detecting the true spread of the virus. “I have taken tests out of a sense of responsibility and from those, I discovered two out of my three infections,” says Polo. “But there are people who haven’t done this and who will never know if they were infected before.” In the summer of 2021, he had tickets to fly to Milan but was unable to travel after testing positive. “The second case was the worst,” he says. For three days, he had a very high fever of 39.5 degrees Celsius.

There are people who haven’t taken tests and who will never know if they were infected before

Bruno Polo

While cases like Polo’s are still the exception, experts warn they will become increasingly common. The Spanish Health Ministry and most of the regions – which are in charge of their healthcare systems, Covid-19 vaccination drives and coronavirus restrictions – do not offer data on reinfections. In Catalonia, however, the health department estimates that 2% of all detected cases in the region since the beginning of the pandemic have been reinfections. In the sixth wave currently affecting Spain, the figure is even higher: up to 5% among the over-50s and up to 8% among the under-50s.

Pere Domingo, the Covid coordinator at Sant Pau Hospital in Barcelona, says there are two main reasons for reinfections. “Either the virus is mutating or a person’s immunity is falling, and in this wave, the two factors have coincided,” he explains.

Domingo points out that the antibodies gained after recovering from the virus start to drop over time, while the omicron variant is able to partially escape the protection of Covid-19 vaccines during the infectious period. “With these factors, transmissibility increases,” he says. Scientific studies, however, confirm that vaccines continue to prevent serious cases of Covid-19. In Catalonia, the health department estimates that in 2021, vaccines prevented between 10,500 and 13,500 intensive care unit (ICU) admissions and between 7,500 and 10,000 deaths.

While it may seem scientifically sound to assume reinfections are more likely to affect people with a weak immune system, this is not always the case. “When you are infected once, your defenses have a certain specificity for each variant,” says Domingo. “And omicron shows it is more capable of inhibiting these very defenses.” This is supported by data from the Catalan government: of the 28,400 people who have had Covid-19 more than once in the past two years, 15,230 (53%) were reinfected with omicron, which became the dominant strain in Catalonia two weeks ago.

“Reinfection is not solely a question of the immune system, but rather of luck with respect to the relations in our social circle,” says Domingo, who knows of another person in Polo’s situation. “A young woman was also infected three times and there is nothing that justifies this immunologically. That’s why the mutation of the virus carries such weight, because her system was perfect.”