Globally, there are a few dozens of people who have been infected by Covid-19 several times. A drop in the ocean when compared to the seven billion humans, but a sufficient number to have scientists worried: if immunity is not guaranteed after being sick, how can a vaccine working in the long run be developed?
A few cases have marked the medical research. There is a patient – reported by the French National Institute for Health and Medical Research (INSERM) – that has been infected twice 142 days apart. He was asymptomatic the second time. Or these two cases reported by l'Express: a female German in her eighties, who died because of reinfection, and a young 25-year-old American male who made it safely despite violent reinfection.
In the first case, an analysis compared with the viral genome held in samples conducted during the first and second infection shown the patient fell sick because of two different layers of SARS-CoV-2.
In other patients, scientists are seeking immune flaw, a patient’s private breach, that could enable to keep hope and see immunity happen in most people. And yet, no bulletproof result has been found.
Searchers also have high hopes in vaccine trials, enabling to study the response of the immune systems when faced with the virus. The INSERM explains these vaccine trials “should lead the way to more precise characterization of the immune response to Covid-19 and the reinfection phenomenon, specifically by identifying the most liable profiles and on what grounds”.
According to Hôpital Saint-Antoine (Paris) head of infectious disease department Karine Lacombe, these reinfection cases are not as rare as we think they are, just a lot harder to spot. In L'Obs, she notices that “currently, all infectious disease specialists are faced with reinfection cases. The phenomenon is not seldom, but it is very difficult to know how many of them there are precisely. All the more so as many of them show no symptom and are not tested”.
How can you know if you caught coronavirus twice? It is difficult and rather counterintuitive. Courrier International explains the process: “for a reinfection to be proven, the patient must have been PCR-tested positive twice, without showing symptoms for at least one month apart the two tests”.
But infectious disease specialist Chantal Reusken from the Dutch National Institute for Public Health and The Environment (RIVM) shows another difficulty, a reality check: it is possible a second screen test turns out positive, not because the patient is sick, but because they keep viral residues in their airways, traces of the virus from the first infection.
