Compared to the Delta variant, Omicron reinfects more. The latest study to certify it is from Imperial College London, according to which two thirds of the people who fell ill with this latest variant had already had Covid in the past.
I study
Researchers from the Real-time Assessment of Community Transmission (REACT) project gathered around 100,000 volunteers across the UK providing them with a molecular test and questionnaire. Of the more than 3,500 people with a positive swab, between 5 and 20 January, 64.5% declared that they had already fallen ill in the past. A further 7.5% say they have probably already had the virus but have never tested themselves to be sure. The number of reinfected is very high, but in part it could have been determined by a flaw in the form of research. As the author himself admits, Professor Paul Elliott, President of Epidemiology and Public Health at Imperial College: “It will take further study to determine how many of these reinfections are genuine and how many are bogus, because it is possible that the swab showed residues of an old infection, possibly from the previous month. We do not know, in fact, when the volunteers contracted Covid for the first time “.
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Omicron beats Delta
The latest data on reinfections in the UK, provided by the Health Security Agency, was of 11%, but with the spread of Omicron the percentage could have risen exponentially. In a previous study, Imperial College had already established that reinfections with Omicron are 5 times more frequent than with Delta. “This research reaffirms what we had already observed in general for other coronaviruses, which is that they do not provide long-term protection from the disease, a bit like the flu,” he says. Fabrizio Pregliasco, virologist of the University of Milan and medical director of Irccs Galeazzi – let’s not forget, then, that this is almost another virus compared to the original Wuhan strain, from which it differs with 32 mutations. It’s like he’s disguised himself with a fake mustache and wig. In this way the immune system does not recognize it immediately, it lets it in and allows reinfection “.
Young people are most affected
“Children and young people were” clean “, because the original Sars-Cov-2 had not affected them much – continues Pregliasco – Today, therefore, they arrive susceptible to infection and Omicron, very contagious, is making them sick, fortunately in most part of the cases with very mild symptoms. Can they reinfect with the same variant? Probably yes, but not before 6-8 months “.
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The dates Iss
From 24 August to 9 January, almost 109,000 cases of people who have recovered from illness were reported in Italy, about 2.7% of the total, according to data from the report of the Istituto Superiore di Sanità. But in the last week considered, the percentage has risen to 3.2. Most people in the age group between 20 and 39 years old, healthcare workers and those who are not vaccinated fall back into the disease. The percentages are low but not very low, so even those who have had a recent infection should not let their guard down (or rather the masks). This is also because the infected person cannot know which variant they were affected by, except in cases where sequencing takes place.
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Omicron, more reinfections
“From the data collected so far,” he emphasizes Claudio Mastroianni, president of the Italian Society of Infectious and Tropical Diseases (Simit) and Professor of Infectious Diseases at Sapienza University of Rome “with the omicron variant the percentage of reinfections is increased up to 5-10 times”. The elements underlying the phenomenon are two. “The first is the presence of numerous mutations that make the variant very different, while the second is its ability to more easily evade the immune system response – although the dose booster has been shown to restore high levels of protection.”
Another ingredient, not to be underestimated, is the increased circulation of the virus in the last period. But the good news is: the second infection generally occurs with less pronounced symptoms, especially if the person is vaccinated. “According to the data”, continues the expert, “those who contracted Sars-Cov-2 with the alpha variant or with the delta are susceptible to omicron, but, if vaccinated, reinfection is generally without symptoms or with mild or moderate “. If the new infection occurs in unvaccinated people, the situation could be a little different, although some scientists speculate that the new disease may still be less serious. “In general – adds Mastroianni – it is good that even those who are cured get vaccinated, according to the timing indicated by the health authorities, to maintain and renew protection”.
When and why reinfection occurs
The new coronavirus is not like other viruses, for example the one responsible for measles, which, unlike Sars-Cov-2, changes little and provides permanent immunity (for which there is no re-inflammation). “Reinfections are associated with different variants,” he explains Mario Clerici, immunologist at the State University of Milan and the Don Carlo Gnocchi Onlus Foundation, “while a second infection with the same viral form is considered highly unlikely, or for example delta-delta or omicron-omicron”. The timing to talk about reinfection is not very clear to date. “Given the coexistence of different variants, such as delta and omicron, in theory a new contagion is possible even in a rather short period”, Clerici clarifies. “We remember that, although omicron is now the most widespread, delta is still present even if in a very limited way”. Delta was dominant until the end of December 2021, so many people infected in this wave contracted the form linked to this variant. In short, those who took delta could in theory recontact themselves with omicron (in rare cases, the opposite could also have happened).
In certain situations, instead of a new contagion, we could find ourselves facing a persistent form. “If the person stops having symptoms and these then reappear after a short time, such as 1 week or 10 days – adds the expert – the initial infection could still be present. In rare cases, a negative de facto false negativization can occur and this leads to mistakenly thinking about a reinfection.