The long Covid remains shrouded in mystery. The mechanisms involved continue to intrigue scientists and doctors. The precise number of patients affected, the duration and severity of their symptoms, as well as the risk factors remain unclear. But in this ocean of uncertainties, good news seems to be emerging. Several recently published studies have confirmed the impressions that came from caregivers in the field: the risk of having persistent symptoms – fatigue, pain, shortness of breath, difficulty concentrating… – after an infection has decreased in recent months. An additional thinning on the front of the Covid, while the most recent waves are less and less intense.
“The figures are not very precise, they vary according to the publications, but all point in the same direction: the rate of Covid long after contamination would have been divided by three or four. The proportion of people affected by these prolonged symptoms would have increased from around 20% of infected subjects to 5%”, notes Professor Antoine Flahault, director of the Institute of Global Health at the University of Geneva (Switzerland).
A study of nearly 3,000 employees of the Swiss healthcare system, published a few days ago, showed that three months after an infection with Omicron, almost all of the infected people had regained a state of health similar to that of the non-infected. . On the contrary, those affected by the Wuhan virus, then by Alpha or Delta, were still suffering from symptoms, for some for more than eighteen months!
Same trend for the most fragile
In the United States, a team of washington post, aided by scientists and the services of a health organization, delved into the medical records of 5 million patients infected during the pandemic. It appears from their analyzes that one patient in 16 would suffer from prolonged symptoms after an infection with Omicron, against one in 12 with the previous variants.
And the trend is just as positive for vulnerable populations, especially those with cancer. A study published in The Lancet Oncology, conducted in 37 healthcare centers in the United Kingdom, Spain, Italy, France, Belgium and Germany showed that in these patients, the risk of developing long-term Covid fell from 17% in 2021 to 6 % more recently. These data confirm the very first publication on the subject, published last summer in the United Kingdom, which already showed, out of 97,000 vaccinated people, a risk of long-term Covid halved between an infection during the waves caused by Delta and those related to Omicron.
But is it related to the variants themselves, or to the increasing immunization of the population, through vaccinations and multiple reinfections? Or to yet other causes? Scientists are struggling to answer this question with precision. “Omicron giving fewer symptoms overall, it is quite possible that there will then be fewer prolonged forms, but this has not yet been clearly demonstrated”, notes Dr Olivier Robineau, infectious disease specialist at Tourcoing hospital and coordinator of the long Covid action of the ANRS-MIE (National Agency for Research on AIDS and Emerging Infectious Diseases).
Paxlovid, also effective against covid long
The role of vaccines could be just as important. A systematic literature review scientific put online on March 23 by the jama (journal of the american medical association) found a 43% reduction in the risk of developing long Covid in people who were doubly vaccinated, compared to those who received no dose. “Several articles show that the more Covid vaccine reminders you have had, the more you are protected from persistent symptoms. This is very much in favor of a causal link”, notes Professor Antoine Flahault.
Treatments could also play a role, and in particular the antiviral Paxlovid, developed by the Pfizer laboratory. This drug already limits serious forms in patients at risk. According to a study conducted on the American Veterans Health Database, it could also reduce the occurrence of prolonged forms of Covid by a quarter. “It is important to note that this benefit was found regardless of the vaccination status of individuals, or their risk factors”, underlined the influential American scientist Eric Topol in his newsletter. The context, less anxiety-provoking than at the start of the pandemic, could also play a role: “We know that the psychological variable can have an impact on the persistence of symptoms. Anxiety and depression are among the risk factors for long Covid” , says Dr. Robineau.
The effect of reinfections is not yet decided. Also from the US Veterans database, an analysis published in naturemedicine last November appeared to show that reinfection increases the risk of death, hospitalization and also persistent symptoms. But according to data released at the end of February by the Office for National Statistics of the United Kingdom, the rate of long Covid would drop from 2.8% after a first infection to 1.6% after a second contamination. “Overall, we still have the impression that when we have been immunized, whether by vaccination or by Covid, we are also protected from these prolonged symptoms. But this remains to be formally demonstrated”, underlines Dr. Robineau.
Anyway, the risk of developing a long Covid does not return to zero. “As there are still many more infections with Omicron, we could have, in absolute value, still many patients with these prolonged symptoms, perhaps even more than during previous periods”, worries the Pr Flahault. How much exactly? Hard to say there too. Public Health France published only one survey on this subject, last June, which reported some two million people affected in the first quarter of 2022. A new survey was carried out at the end of last year, but its results will not be known for several weeks. “Some of the patients end up curing after a few months. But others unfortunately keep symptoms for more than a year and remain very handicapped in their daily life”, notes Dr. Robineau.
These “very long Covids”, as the authors called them from a recent study, will they also be less frequent in the future? It is too early to tell. But it is to be hoped, because today, medicine still lacks answers for these patients.