Effectiveness of first and second boost COVID-19 vaccination in healthy adults during BA.5.2/BF.7 surge in China.

With the development of the SARS-CoV-2 pandemic, there have been doubts about the necessity of vaccine boosters for healthy adults. However, due to the lack of relevant evidence, current research is unable to provide reliable medical advice for COVID-19 boost in healthy adults. We conducted a retrospective observational study to evaluate the effectiveness of different COVID-19 vaccination regimens by investigating the SARS-CoV-2 infection status of healthy donors in Southeast China. From December 2022 to February 2023, 737 healthy adult blood donors were analyzed. Results showed that any COVID-19 vaccine boosts reduced the risk of Omicron BA.5.2/BF.7 infection compared to only receiving prime vaccination (rVE = 16%, 95%CI = 4, 27%). The second boost further enhanced vaccine effectiveness compared to the received first booster (rVE = 39%, 95%CI = 16, 55%). Through retrospective observation of healthy adults during the BA.5.2/BF.7 surge in China, we found that boost vaccinations significantly reduce the risk of SARS-CoV-2 infection and disease. Findings show healthy adults benefit from boost vaccinations, even if not at high-risk for severe COVID-19.

The duration and breadth of antibody responses to 3-dose of inactivated COVID-19 vaccinations in healthy blood donors: An observational study.

Objectives: We aimed to evaluate the duration and breadth of antibodies elicited by inactivated COVID-19 vaccinations in healthy blood donors. Methods: We performed serological tests on 1,417 samples from 658 blood donors who received two (n=357), or three (n=301) doses of COVID-19 inactivated vaccine. We also accessed the change in antibody response before and after booster vaccination in 94 participants and their neutralization breadth to the current variants after the booster. Results: Following vaccination, for either the 2- or 3-dose, the neutralizing antibodies (nAbs) peaked with about 97% seropositivity approximately within one month but subsequently decreased over time. Of plasmas collected 6-8 months after the last immunization, the nAb seropositivities were 37% and 85% in populations with 2-dose and 3-dose vaccinations, respectively. The nAbs of plasma samples (collected between 2-6 weeks after the 3rd dose) from triple-vaccinated donors (n=94) showed a geometric mean titer of 145.3 (95% CI: 117.2 to 180.1) against the ancestral B.1, slightly reduced by 1.7-fold against Delta variant, but markedly decreased by 4-6 fold in neutralizing Omicron variants, including the sub-lineages of BA.1 (5.6-fold), BA.1.1 (6.0-fold), BA.2 (4.2-fold), B.2.12.1 (6.2-fold) and BA.4/5 (6.5-fold). Conclusion: These findings suggested that the 3rd dose of inactivated COVID-19 vaccine prolongs the antibody duration in healthy populations, but the elicited-nAbs are less efficient in neutralizing circulating Omicron variants.

Influence of sodium-modified Ni/SiO2 catalysts on the tunable selectivity of CO2 hydrogenation: Effect of the CH4 selectivity, reaction pathway and mechanism on the catalytic reaction.

CO2 hydrogenation over Ni/SiO2 catalysts with and without Na additives was investigated in terms of the catalytic activity, selectivity of CO2 methanation and reaction mechanism. Na additives could cause the formation of Na2O species that might deposit on the Ni surface of Ni/SiO2 (NiNax/SiO2). When the Ni metal is partially covered with Na2O species, a highly positive charge on the Ni metal could occur compared to the original Ni/SiO2 catalyst. The addition of Na to the Ni/SiO2 catalyst could influence selectivity toward CO formation. The adsorbed formic acid is the major intermediate on the Ni/SiO2 catalyst during CO2 hydrogenation. The formic acid species might decompose into adsorbed CO complexes in the forms of linear CO, bridged CO and multibonded CO. CH4 formation should be ascribed to the hydrogenation of these adsorbed CO complexes. The Ni/SiO2 catalyst with the Na additive might have very weak ability for H2 and CO adsorption, thus making it difficult for CO methanation to occur. The hydrogen carbonate species adsorbed on the NiNax/SiO2 catalysts were proposed to be the key intermediate, and they might decompose to CO or be hydrogenated to form CH4.

Tiny Ni particles dispersed in platelet SBA-15 materials induce high efficiency for CO2 methanation.

In this study, short-channel SBA-15 with a platelet morphology (p-SBA-15) is used to support Ni to effectively enhance catalytic activity and CH4 selectivity during CO2 hydrogenation. The use of p-SBA-15 as a support can result in smaller Ni particle sizes than Ni particles on typical SBA-15 supports because p-SBA-15 possesses a larger surface area and a greater ability to provide metal-support interactions. The Ni/p-SBA-15 materials with tiny Ni particles exhibit enhanced catalytic activity toward CO2 hydrogenation and CH4 formation during CO2 hydrogenation compared to the same Ni loading on a SBA-15 support. The presence of metal-support interaction on the Ni/p-SBA-15 catalyst may increase the possibility of abundance of strongly adsorbing sites for CO and CO2, thus resulting in high reaction rates for CO2 and CO hydrogenation. The reaction kinetics, reaction pathway and active sites were studied and correlated to the high catalytic activity for CO2 hydrogenation to form CH4.

Synthesis of sub-nanosized Pt particles on mesoporous SBA-15 material and its application to the CO oxidation reaction.

In this work, we show that the size and shape of Pt nanoparticles in SBA-15 can be controlled through vacuum and air calcination. The vacuum-calcination/H2-reduction process is used to thermally treat a 0.2 wt% Pt(4+)/SBA-15 sample to obtain small 2D clusters and single atoms that can significantly increase Pt dispersion in SBA-15. Compared with thermal treatments involving air-calcination/H2-reduction, which result in ∼4.6 nm rod-like Pt particles, vacuum-calcination/H2-reduction can dramatically reduce the size of the Pt species to approximately 0.5-0.8 nm. The Pt particles undergoing air-calcination/H2-reduction have poor conversion efficiency because the fraction of terrace sites, the major sites for CO oxidation, on the rod-like Pt particles is small. In contrast, a large amount of low-coordinated Pt sites associated with 2D Pt species and single Pt atoms in SBA-15 is effectively generated through the vacuum-calcination/H2-reduction process, which may facilitate CO adsorption and induce strong reactivity toward CO oxidation. We investigated the effect of vacuum-calcination/H2-reduction on the formation of tiny 2D clusters and single atoms by characterizing the particles, elucidating the mechanism of formation, determining the active sites for CO oxidation and measuring the heat of CO adsorption.