Abstract Data about the duration of humoral response following COVID-19 vaccines are mandatory to establish appropriate population vaccination strategy. This study reports on the antibody decline observed in a population of COVID-19 naïve and COVID-19 positive individuals having received the two dose regimen of the BNT162b2 vaccine. Six months after vaccination, a significant antibody decline was observed in both COVID-19 naïve and positive individuals. The estimated half-life of total and IgG antibodies differs and ranges from several months for total antibodies to only several weeks for IgG antibodies, explaining the significant proportions of participants with non-detectable levels of neutralizing antibodies at 6 months. Whether this decrease correlates with an equivalent drop in the clinical effectiveness against the virus will require appropriate clinical studies. Nevertheless, these data are already important to support the decision-making on the potential use of a booster dose.
Abstract Evidence about the long‐term persistence of the booster‐mediated immunity against Omicron is mandatory for pandemic management and deployment of vaccination strategies. A total of 155 healthcare professionals (104 COVID‐19 naive and 51 with a history of SARS‐CoV‐2 infection) received a homologous BNT162b2 booster. Binding antibodies against the spike protein and neutralizing antibodies against Omicron were measured at several time points before and up to 6 months after the booster. Geometric mean titers of measured antibodies were correlated to vaccine efficacy (VE) against symptomatic disease. Compared to the highest response, a significant 10.2‐ and 11.5‐fold decrease in neutralizing titers was observed after 6 months in participants with and without history of SARS‐CoV‐2 infection. A corresponding 2.5‐ and 2.9‐fold decrease in binding antibodies was observed. The estimated T 1/2 of neutralizing antibodies in participants with and without history of SARS‐CoV‐2 infection was 42 (95% confidence interval [CI]: 25–137) and 36 days (95% CI: 25–65). Estimated T 1/2 were longer for binding antibodies: 168 (95% CI: 116–303) and 139 days (95% CI: 113–180), respectively. Both binding and neutralizing antibodies were strongly correlated to VE ( r = 0.83 and 0.89). However, binding and neutralizing antibodies were modestly correlated, and a high proportion of subjects (36.7%) with high binding antibody titers (i.e., >8434 BAU/ml) did not have neutralizing activity. A considerable decay of the humoral response was observed 6 months after the booster, and was strongly correlated with VE. Our study also shows that commercial assays available in clinical laboratories might require adaptation to better predict neutralization in the Omicron era.
Abstract Studies about the evaluation of the humoral and cellular response following the bivalent booster administration are still scarce. The aim of this study was to assess the humoral and cellular response in a cohort of healthcare workers that received either the BA.1 or the BA.4/5 bivalent booster.Blood samples from participants were collected before the administration of either the BA.1 or BA.4/5 bivalent booster from Pfizer-BioNTech and after 14, 28, and 90 days. The humoral response was evaluated using neutralizing antibodies against the BA.5 Omicron variant and binding total and IgG antibodies. The cellular response was assessed by measurement of the release of interferon gamma (IFNγ) from T cells in response to an in vitro SARS-CoV-2 stimulation.Although most participants still had a robust cellular response before the booster, a significant increase in the cellular response was observed after 2 weeks, especially in participants presenting lower levels of IFNγ before the booster administration. Levels of IFNγ remained stable at 3 months and contrast sharply with the rapid decrease of BA.5-specific neutralizing antibodies. Binding antibodies were only modestly correlated to the neutralizing capacity. The evolution of the humoral and cellular response was non-significantly different between participants that received the BA.1 or the BA.4/5 bivalent booster. The monitoring of the humoral and cellular response could be useful to identify patients with a poor adapted immunity that would need to benefit first from an additional booster shot.
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(1) Background: The detection of SARS-CoV-2 RNA in nasopharyngeal samples through real-time reverse transcription-polymerase chain reaction (RT-PCR) is considered the standard gold method for the diagnosis of SARS-CoV-2 infection. Antigen detection (AD) tests are more rapid, less laborious, and less expensive alternatives but still require clinical validation. (2) Methods: This study compared the clinical performance of five AD tests, including four rapid AD (RAD) tests (biotical, Panbio, Healgen, and Roche) and one automated AD test (VITROS). For that purpose, 118 (62.8%) symptomatic patients and 70 (37.2%) asymptomatic subjects were tested, and results were compared to RT-PCR. (3) Results: The performance of the RAD tests was modest and allowed us to identify RT-PCR positive patients with higher viral loads. For Ct values ≤25, the sensitivity ranged from 93.1% (95% CI: 83.3–98.1%) to 96.6% (95% CI: 88.1–99.6%), meaning that some samples with high viral loads were missed. Considering the Ct value proposed by the CDC for contagiousness (i.e., Ct values ≤33) sensitivities ranged from 76.2% (95% CI: 65.4–85.1%) to 88.8% (95% CI: 79.7–94.7%) while the specificity ranged from 96.3% (95% CI: 90.8–99.0%) to 99.1% (95% CI: 95.0–100%). The VITROS automated assay showed a 100% (95% CI: 95.5–100%) sensitivity for Ct values ≤33, and had a specificity of 100% (95% CI: 96.6–100%); (4) Conclusions: Compared to RAD tests, the VITROS assay fully aligned with RT-PCR for Ct values up to 33, which might allow a faster, easier and cheaper identification of SARS-CoV-2 contagious patients.
Abstract The diagnostic of SARS-CoV-2 infection relies on reverse transcriptase polymerase chain reactions (RT-PCR) performed on nasopharyngeal (NP) swabs. Nevertheless, false negative results can be obtained with inadequate sampling procedures making the use of other matrices of interest. This study aims at evaluating the kinetic of serum N antigen in severe and non-severe patients and compare the clinical performance of serum antigenic assays with NP RT-PCR. Ninety patients were included and monitored for several days. Disease severity was determined according to the WHO clinical progression scale. The serum N antigen was measured with a chemiluminescent assay (CLIA) and the Single Molecular Array (Simoa). Thresholds for severity were determined. In severe patients, the peak antigen response was observed 7 days after the onset of symptoms followed by a decline. No peak response was observed in non-severe patients. Severity threshold for the Simoa and the CLIA provided positive likelihood ratio of 30.0 and 10.9 for the timeframe between day 2 and day 14, respectively. Compared to NP RT-PCR, antigenic assays were able to discriminate the severity of the disease (p = 0.0174, 0.0310 and p = 0.1551 with the Simoa, the CLIA and the NP RT-PCR, respectively). Sensitive N antigen detection in serum thus provides a valuable new marker for COVID-19 diagnosis and evaluation of disease severity. When assessed during the first 2 weeks since the onset of symptoms, it may help in identifying patients at risk of developing severe COVID-19 to optimize better intensive care utilization.
Vaccines against SARS-CoV-2 were developed during the pandemic including the BNT162b2 the mRNA-1273. We evaluate the levels of binding antibodies against the receptor binding domain and the levels of NAbs in individuals who developed a breakthrough infection after having received three doses of mRNA-1273. A total of 51 participants were included. The breakthrough group was compared to a 1:1 matched-control group. Among the 51 individuals, 18 (35%) developed a breakthrough infection. The GMT of NAbs against the BA.1 in the BK population was 278.1 (95%CI: 168.1–324.1). This titer was significantly lower compared to the matched-control group when considering all data (GMT = 477.4; 95%CI: 316.2–541.0; p = 0.0057). Results were similar for the BA.5 (GMT = 152.0 (95%CI: 76.9–172.9) for breakthrough and 262.0 (95%CI: 171.3–301.8) for control (p = 0.0043)). Our study found that individuals receiving the mRNA-1273 booster and who developed a breakthrough infection presented lower levels of binding antibodies and NAbs before the infection as compared to a matched-control group.
Some studies suggest that the monovalent mRNA-1273 vaccine is more effective than BNT162b2 in producing higher levels of antibodies. However, limited data are available, and the methods used are not directly comparable.
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