Establishing serum pathogen neutralization approaches for assaying the induced immune replies remain the yellow metal standard. in recipients not really contaminated with SARS-CoV-2 previously, it appears that mRNA vaccine of Pfizer/BioNTech shows a higher efficiency in comparison to inactivated pathogen vaccines. COVID-19 convalescent individuals have generated poor antibody responses. Nevertheless, when they are vaccinated with any brand of the COVID-19 vaccines, many of them mounted an exponential increase of the induced immune responses, qualified as a hybrid vigor immunity. Our developed in-house ELISA seems to be very efficient in evaluating the effectiveness of anti-COVID-19 vaccination. Platforms based on mRNA vaccine are better performing than those based on inactivated virus. values lower than 0.05 are significant at the 95% confidence interval and higher than that are not significant. We have used the USA-Food and Drug Administration (FDA) calculator available on its website to calculate the positive and negative predictive values, on the basis of a prevalence arbitrary fixed by this calculator at 5%. For the calibration accuracy from plate to plate, 100 samples were assayed twice. The means were compared by the paired sample t-test using MedCalc Software. The null hypothesis is that the average of the differences between the paired observations in the two samples is zero. If the calculated value is less than 0.05, the conclusion is that, statistically, the mean difference between the paired observations is significantly different from 0. Results Validation of an in-house ELISA We have estimated the qualitative (seropositive or seronegative) performances of our in-house ELISA using several COVID-19 RT-PCR positive samples. ROC analysis (Fig.?2) gave us very satisfactory performances, the overall sensitivity was 96%, CI95% [91.5C98.5%] and the sensitivity after D14 is 95.9%, CI95% [89.8C98.9%] (93 true positive out of 97 patients sampled after D14). For the specificity calculation, we have used 116 pre-pandemic sera collected in 2017 as true negative sera. The specificity of our in-house ELISA was 97.5%, CI95% [92.8C99.5%]. The accuracy of the test was very high 0.968, CI95% [0.939C0.985] and the positive and negative predictive values were 66.7%, CI95% [39.6C85.9%] and 99.8%, CI95% [99.4C99.9%], respectively. The calibration accuracy was guaranteed by using a positive control, a negative Dodecanoylcarnitine control as well as 2 calibrators. In addition, the paired sample t-test gave a value of 0.3562, far higher than 0.05. Therefore, the mean difference between the paired observations is not significantly different from 0 and the accuracy of the given results from plate to plate are robust. The comparison of our qualitative results to those of the Vidas anti-RBD and Elecsys anti-N showed better performances than the former (AUC 0.841, CI95% [0.727C0.883], value? ?0.05) but similar performances with the latter (0.885, CI95% [0.808C0.938], value? ?0.05) (Fig.?3). Therefore, our developed in-house ELISA is at least as good as the commercial techniques. Open in a separate window Figure 2 ROC curve for the in-house ELISA using optical density values. Open in a separate window Figure 3 Comparison between the in-house ELISA qualitative results and those of the automated tests Vidas SARS-CoV-2 IgG anti-RBD Biomrieux and Elecsys Anti-Nucleocapsid of SARS-CoV-2 Roche. Next, we compared the quantitative results of our in-house ELISA to those of the Mef2c commercial cPass GenScript FDA-EUA. Correlation between anti-S titers and percentage of inhibition by the surrogate sero-neutralization ELISA showed a strong correlation (r?=?0.5, CI95% [0.236C0.696], value? ?0.05) (Fig.?4). Open in a separate window Figure 4 Correlation between the antibody titers (BAU/ml) of the in-house ELISA and the inhibition percentage by the surrogate neutralization ELISA (cPass GenScript). According to the cPass a cut-off of 30% is recommended Dodecanoylcarnitine by the manufacturer as an indicator of the presence of virus neutralizing antibodies. In extrapolation of our in-house test, this corresponds to serums with titers of 59?BAU/ml. Evaluation of the Dodecanoylcarnitine humoral immune responses induced by different COVID-19 vaccines The in-house validated ELISA for COVID-19 serology seems to be efficient in assessing the immune responses induced by the different vaccines used in the National Vaccination Program of Tunisia. We have analyzed 115 recipients of.