Teams from Strasbourg University Hospital and the Institut Pasteur carried out a study among hospital staff on the two sites of Strasbourg University Hospital. After observing 160 people with minor forms of COVID-19, the scientists concluded that nearly all the patients developed antibodies within two weeks of being infected. In 98% of the patients, neutralizing antibodies were detected after 28 days. This suggests that even those with minor forms of the disease develop antibodies that could confer immunity for several weeks following infection. The results were presented in a pre-publication on the MedRxiv website.
The immunological response of individuals who contract minor forms of SARS-CoV-2 infection is still poorly characterized.
Teams from Strasbourg University Hospital and the Institut Pasteur studied 160 volunteers, all members of hospital staff from the two sites of Strasbourg University Hospital, who were infected by SARS-CoV-2 (with a positive diagnosis after a PCR test) and developed minor forms of the illness that did not require admission to hospital.
The presence of anti-SARS-CoV-2 antibodies was measured using two techniques, a rapid diagnostic test and a test known as S-Flow developed by the Institut Pasteur. The neutralizing activity of the antibodies was measured with a pseudovirus neutralization assay.
The median time between when the symptoms emerged and the blood samples were taken was 24 days (between 13 and 39 days). The rapid immunodiagnostic test detected antibodies in 153 (95.6%) of the samples and the S-Flow test detected antibodies in 159 (99.4%) of the samples. Neutralizing antibodies (NAbs) were detected in 79%, 92% and 98% of the samples, respectively 13-20, 21-27 and 28-41 days after the emergence of symptoms.
The study demonstrates that SARS-CoV-2 antibodies are present in virtually all hospital staff who previously tested positive by PCR. The neutralizing activity of the antibodies increases over time, suggesting that people are developing potentially protective immunity.
"We knew that individuals with severe forms of the illness were developing antibodies within 15 days of the start of symptoms. We now know that the same is true for those with minor forms, even if the antibody levels are likely to be lower," comments Arnaud Fontanet, one of the authors of the study and Head of the Institut Pasteur's Department of Global Health.
"Our study shows that in most cases, antibody levels are compatible with protection against new infection with SARS-CoV-2 for at least 40 days after the beginning of symptoms. The aim now is to evaluate the long-term persistence of the antibody response and its neutralizing capacity in these healthcare workers," explain Timothée Bruel, a scientist in the Institut Pasteur's Virus and Immunity Unit, and Olivier Schwartz, Head of the Unit.
"The results of this study are very encouraging for people already infected by the virus. Even after developing a mild form of COVID-19, they are capable of generating protective antibodies that are present at least 40 days after the emergence of symptoms. We now need to verify the persistence of these antibodies over time. The results are also good news for future vaccine strategies," concludes Professor Samira Fafi-Kremer, Head of the Virology Department at Strasbourg University Hospital and first author of the study.
Serologic responses to SARS-CoV-2 infection among healthcare workers with mild disease in eastern France, MedRxiv, May 22, 2020
Samira FAFI-KREMER1,2*, Timothée BRUEL3*, Yoann MADEC4, Rebecca GRANT4, Laura TONDEUR4, Ludivine GRZELAK3,5, Isabelle STAROPOLI3, François ANNA6, Philippe SOUQUE7, Catherine SCHMIDTMUTTER8, Nicolas COLLONGUES8, Alexandre BOLLE8, Aurélie VELAY1,2, Nicolas LEFEBVRE9, Marie MIELCAREK10, Nicolas MEYER10,11, David REY12, Pierre CHARNEAU6,7, Bruno HOEN16, Jérôme De SEZE8,17, Olivier SCHWARTZ3** and Arnaud FONTANET4,18**
1 CHU de Strasbourg, Laboratoire de virologie, F-67091 Strasbourg, France
2 Université de Strasbourg, INSERM, IRM UMR_S 1109, Strasbourg, France.
3 Virus & Immunity Unit, Department of Virology, Institut Pasteur, Paris, France, CNRS UMR 3569, Paris, France; Vaccine Research. Institute, Creteil, France
4 Institut Pasteur, Emerging Diseases Epidemiology Unit, Paris, France
5 Université de Paris, Sorbonne Paris Cité, Paris, France
6 Pasteur-TheraVectys joined unit
7 Molecular Virology & Vaccinology Unit, Department of Virology, Institut Pasteur, Paris, France
8 Centre d’investigation Clinique INSERM 1434 Strasbourg, France
9 CHU de Strasbourg, Service des infectieuses et tropicales, F-67091 Strasbourg, France
10 CHU de Strasbourg, Service de santé Publique, GMRC, F-67091 Strasbourg, France
11 Université de Strasbourg, CNRS, iCUBE UMR 7357, Strasbourg, France
12 CHU de Strasbourg, Pôle SMO, le Trait d’Union, F-67091 Strasbourg, France
13 Molecular Genetics of RNA Viruses, Department of Virology, Institut Pasteur CNRS UMR 3569, Université de Paris, Paris, France
14 National Reference Center for Respiratory Viruses, Institut Pasteur, Paris, France
15 Center for Innovation and Technological Research, Institut Pasteur, Paris, France
16 Direction de la recherche médicale, Institut Pasteur, Paris, France
17 CHU de Strasbourg, Service de Neurologie, F-67091 Strasbourg, France
18 Conservatoire National des Arts et Métiers, PACRI Unit, Paris, France
* Co-first authors
** Co-last authors