Persistent symptoms after a Covid-19 infection – exhaustion, headaches, muscle aches, depression, etc. -, called “long Covid”, or “post-Covid syndrome”, are still poorly understood. No specific treatment (which would cure the symptoms) is yet available. While waiting for better, doctors offer symptomatic treatments (which act on the symptoms). But one thing is certain, the “long Covid” is a public health problem.
“The epidemiological data remain very variable depending on the source, but if we take the definition of the World Health Organization – symptoms prolonged beyond three months after infection – 10% of infected people would be affected. “, explains Dominique Le Guludec, president of the High Authority for Health. That is, in the long term, nearly 2 million French people… According to the General Directorate of Health (DGS), the patients would already be 1 million, “of which 100,000 would require care in dedicated structures”.
Vaccination would reduce the risk of developing persistent symptoms
Good news is emerging, however: vaccines seem effective against long Covid. Firstly because they reduce the risk of being contaminated and above all because they reduce the severity of the disease. “However, the severity of symptoms during infection is a risk factor for ‘Covid long'”, explains Dr. Olivier Robineau, specialist in infectious diseases at the Center Hospitalier de Tourcoing, which hosts a “Covid long” service. For its part, the General Directorate of Health, questioned by L’Express, estimates that “vaccination reduces the risk of presenting persistent signs by 50%.
A preliminary study (the results of which have not yet been peer-reviewed), published by Israeli researchers on January 17, also demonstrates that people vaccinated (with Pfizer-BioNTech) and infected with Sars-CoV-2 report much fewer persistent symptoms than those who have been infected without being vaccinated. The researchers asked more than 3,388 people – all of whom tested positive for Covid-19 between March 2020 and November 2021 – if they suffered from the most common symptoms of Covid Long several weeks after an infection. They found that people who received two doses were 54% less likely to report headaches, 64% less likely to report fatigue and 68% less likely to report muscle aches than the unvaccinated.
While this pre-study still needs to be validated, it is one of the most comprehensive and accurate to date. It also confirms the results of a British study, published on September 1, 2021 in The Lancet, which indicates that vaccination would halve the risk of developing persistent symptoms. “It is positive to see that different studies come to the same results,” says near Nature Dr Claire Steves, lecturer at King’s College London, who directed this work.
The vaccine as a treatment for Covid-19?
Researchers are also trying to find out if vaccines could be used as a “treatment” for post-Covid symptoms in order to cure or even reduce symptoms. “The data is lacking, but we find that some patients suffering from “Covid Long” may see their signs disappear after vaccination, others in whom they persist and still others for whom the symptoms are exacerbated”, tells us Olivier Schwartz. , head of the Virus and Immunity Unit at the Institut Pasteur.
In a study prepublished in The Lancet September 29, 2020, French and American researchers, for example, suggest that vaccination reduced the intensity and improved the lives of patients with persistent symptoms. In this work, the scientists studied 910 “Covid Long” patients, 455 who received a single dose of vaccine and 455 who were not vaccinated. The results indicate that after 3 months, 16.6% of patients in the vaccinated group report remission of all symptoms of long COVID, compared to 7.5% in the control group. “Vaccination results in improved symptoms in patients with Covid Long. These results support the hypothesis that, for at least some patients, persistent symptoms could be explained by a persistent viral reservoir and/or by fragments of circulating viruses”, indicate the authors of the study.
Of course, it should be emphasized that this study has not yet been published, and should therefore be taken with caution. “Immunological speculations seem risky to me as long as we do not have convincing explanations of the physiopathological mechanisms [NDLR : les mécanismes qui expliqueraient comment le Covid-19 peut provoquer des symptômes persistants], points out for his part Xavier de Lamballerie, professor of medicine, specialist in medical virology at the Public Assistance-Hospitals of Marseille. We can speculate endlessly, but for now the purpose of vaccination is to prevent further infection or at least a severe form, not to cure long Covid, and there is no robust data to suggest opposite”.
An analysis shared by Mathieu Molimard, head of the medical pharmacology department at the Bordeaux University Hospital: “We know that vaccination partly protects against Covid infection and reduces serious forms, so it is quite logical that it allows to reduce the occurrence of long Covid, but can an injection cure the symptoms in those affected? At this stage, we don’t know. Especially since in what is called “long Covid” , there is an association of symptoms that are not necessarily related to the others, the mechanisms explaining them are not necessarily the same, and the treatments may be different.
The vaccine responsible for Covid long?
Another question agitates part of the scientific community, that of the possibility that vaccines can, on very rare occasions (probably less than one case in 100,000), cause persistent symptoms. Review Science approach the subject cautiously in a long article citing the case of a handful of people never infected with Covid-19, but complaining of persistent health problems after being vaccinated. Researchers from the National Institutes of Health (NIH, USA) conducted the survey in January 2021, but their study, which is based on a small number of patients, did not prove a link between vaccination and the occurrence of these symptoms.
Other preclinical and mouse studies suggest that antibodies targeting the Spike protein of Sars-CoV-2, the same protein used by vaccines to trigger a protective immune response, could cause collateral damage. “Researchers have studied monoclonal antibodies which appear when infected or vaccinated and which seem to have a tropism for tissues of the hippocampus [NDLR : dans le cerveau]. They could attack these healthy tissues, which suggests a potential autoimmune effect, which could be linked to certain persistent symptoms”, underlines Hervé Fleury, virologist and professor emeritus at the CNRS and the University of Bordeaux.
The specialist, a strong supporter of vaccination, believes that this preliminary research calls for caution regarding the multiplication of vaccine injections in order to counter new variants. “The results are not worrying, but they must be taken into consideration and not rule out the risk of mechanisms of over-stimulation of the immune system which could favor the appearance of these potential autoimmunity phenomena”, he warns.
If this track remains explored by scientists, they know that they are walking on eggshells. Studying the side effects of vaccines is important, but it can also fuel fears – and antivax delusions – when they are safe, effective and save lives. Above all, even if the vaccines would induce persistent symptoms, they would be extremely rare, while, at the same time, 10% of people infected with Sars-CoV-2 seem to be affected more than three months after infection. “A vaccine can cause side effects which, until proven otherwise, are never different from the negative effects related to infection, except that the side effects of vaccines are always less frequent, less serious and less long-lasting than those of the disease”, recalls Mathieu Molimard.