Exploring the humoral immunity response to SARS-CoV-2 post vaccination and post infection
ASSAID N. 1,2, ARICH S. 2, AKARID K. 1, CHAROUTE H. 2, EZZIKOURI S. 2, MAAROUFI A. 2
1 Health and Environment Laboratory, Molecular Genetics and Immunophysiopathology Research Team, Aïn Chock Faculty of Sciences, University of Hassan II Casablanca (UH2C, Casablanca, Morocco; 2 Service de Parasitologie et des Maladies Vectorielles, Institut Pasteur du Maroc, Casablanca, Morocco
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses serious global public health problems. Characterization of humoral response, is important for establishing vaccine strategies. First, we assessed kinetics of anti-SARS-CoV-2 antibodies against spike protein for 3 months following symptom onset, in a cohort of COVID-19 patients. Secondly, we studied the level of IgG antibodies against SARS-CoV-2 five months after complete vaccination with Covishield or BBIBP-CorV, in Moroccan healthcare workers. We enrolled patients at two regional hospitals in Casablanca, Morocco. In parallel, we collected samples from 82 participants who were fully vaccinated with ChAdOx1 nCoV-19 or BBIBP-CorV. Blood samples were collected and N-specific IgM and S-specific IgG levels were measured by ELISA. IgM antibodies were assessed 2–5(D00), 9–12(D07), 17–20(D15), and 32–37(D30) days after symptom onset. IgG antibodies were assessed at these time points plus 60 (D60) and 90 (D90) days after symptom onset. We found that at 3 months after symptom onset, 79% of patients had detectable SARS-CoV-2-specific IgG, whereas their IgM seropositivity was 19% by 1 month after symptom onset. The IgM level decreased at 1 month after symptom onset, whereas the IgG level peaked at D30 and remained almost stable at D90 (2.95; IQR 1.52–5.19). IgG levels were significantly higher in patients older than 50 years at all follow-up time points (P < 0.05). No significant difference were reported based on gender or comorbidities. Of the 82 participants, we report that 65.85% and 86.59% were positive for IgG by ELISA and Abbott Architect™ tests, respectively. The median level of anti-S1 antibodies reported for the two vaccines was almost similar according to the two tests. No significant differences were reported between the positivity rates of those vaccinated, either for sex or for age. Our study provides information on the longevity of anti-SARS-CoV-2 antibodies after infection or vaccination.