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Background: Understanding the neutralizing antibody (NAb) titer against COVID-19 over time is important to provide information for vaccine implementation. The longitudinal NAb titer over one year after SARS-CoV-2 infection is still unclear. The purposes of this study are to evaluate the duration of the neutralizing NAb titers in COVID-19 convalescents and factors associated with the titer positive duration., Methods: A cohort study followed COVID-19 individuals diagnosed between 2020 and 2021 May 15th from the COVID-19 database from the Taiwan Centers for Disease Control. We analyzed NAb titers from convalescent SARS-CoV-2 individuals. We used generalized estimating equations (GEE) and a Cox regression model to summarize the factors associated with NAb titers against COVID-19 decaying in the vaccine-free population., Results: A total of 203 convalescent subjects with 297 analytic samples were followed for a period of up to 588 days. Our study suggests that convalescent COVID-19 in individuals after more than a year and four months pertains to only 25% of positive titers. The GEE model indicates that longer follow-up duration was associated with a significantly lower NAb titer. The Cox regression model indicated the disease severity with advanced condition was associated with maintaining NAb titers (adjusted hazard ratio: 2.01, 95% CI: 1.11-3.63) and that smoking was also associated with higher risk of negative NAb titers (adjusted hazard ratio: 0.55, 95% CI: 0.33-0.92)., Conclusions: Neutralizing antibody titers diminished after more than a year. The antibody titer response against SARS-CoV-2 in naturally convalescent individuals provides a reference for vaccinations., Competing Interests: Declaration of competing interest The authors have no conflicts of interest., (Copyright © 2023. Published by Elsevier B.V.)

Background: MVC-COV1901, a recombinant protein vaccine containing pre-fusion-stabilised spike protein S-2P adjuvanted with CpG 1018 and aluminium hydroxide, has been shown to be well tolerated with a good safety profile in healthy adults aged 20-49 years in a phase 1 trial, and provided a good cellular and humoral immune responses. We present the interim safety, tolerability, and immunogenicity results of a phase 2 clinical trial of the MVC-COV1901 vaccine in Taiwan., Methods: This is a large-scale, double-blind, randomised, placebo-controlled phase 2 trial done at ten medical centres and one regional hospital in Taiwan. Individuals aged 20 years or older who were generally healthy or had stable pre-existing medical conditions were eligible for enrolment. Exclusion criteria included (but were not limited to) travel overseas within 14 days of screening, intention to travel overseas within 6 months of the screening visit, and the absence of prespecified medical conditions, including immunosuppressive illness, a history of autoimmune disease, malignancy with risk to recur, a bleeding disorder, uncontrolled HIV infection, uncontrolled hepatitis B and C virus infections, SARS-CoV-1 or SARS-CoV-2 infections, an allergy to any vaccine, or a serious medical condition that could interfere with the study. Study participants were randomly assigned (6:1) to receive two doses of either MVC-COV1901 or placebo, administered via intramuscular injection on day 1 and day 29. MVC-COV1901 contained 15 μg of S-2P protein adjuvanted with 750 μg CpG 1018 and 375 μg aluminium hydroxide in a 0·5 mL aqueous solution, and the placebo contained the same volume of saline. Randomisation was done centrally by use of an interactive web response system, stratified by age (≥20 to <65 years and ≥65 years). Participants and investigators were masked to group assignment. The primary outcomes were to evaluate the safety, tolerability, and immunogenicity of MVC-COV1901 from day 1 (the day of the first dose) to day 57 (28 days after the second dose). Safety was assessed in all participants who received at least one dose. Immunogenicity was assessed by measuring geometric mean titres (GMTs) and seroconversion rates of neutralising antibody and antigen-specific IgG in the per-protocol population. This study is registered with ClinicalTrials.gov, NCT04695652., Findings: Of 4173 individuals screened between Dec 30, 2020, and April 2, 2021, 3854 were enrolled and randomly assigned: 3304 to the MVC-COV1901 group and 550 to the placebo group. A total of 3844 participants (3295 in the MVC-COV1901 group and 549 in the placebo group) were included in the safety analysis set, and 1053 participants (903 and 150) had received both doses and were included in the per-protocol immunogenicity analysis set. From the start of this phase 2 trial to the time of interim analysis, no vaccine-related serious adverse events were recorded. The most common solicited adverse events in all study participants were pain at the injection site (2346 [71·2%] of 3295 in the MVC-COV1901 group and 128 [23·3%] of 549 in the placebo group), and malaise or fatigue (1186 [36·0%] and 163 [29·7%]). Fever was rarely reported (23 [0·7%] and two [0·4%]). At 28 days after the second dose of MVC-COV1901, the wild-type SARS-CoV-2 neutralising antibody GMT was 662·3 (95% CI 628·7-697·8; 408·5 IU/mL), the GMT ratio (geometric mean fold increase in titres at day 57 vs baseline) was 163·2 (155·0-171·9), and the seroconversion rate was 99·8% (95% CI 99·2-100·0)., Interpretation: MVC-COV1901 has a good safety profile and elicits promising immunogenicity responses. These data support MVC-COV1901 to enter phase 3 efficacy trials., Funding: Medigen Vaccine Biologics and Taiwan Centres for Disease Control, Ministry of Health and Welfare., Competing Interests: Declaration of interests CC, CEL, and I-CT are employees of Medigen Vaccine Biologics (Taipei, Taiwan) and they report receiving grants from Taiwan Centres for Disease Control, Ministry of Health and Welfare, during the conduct of the study. CC also has a patent pending relating to the MVC-COV1901 vaccine against SARS-CoV-2 (US17/351,363). All other authors declare no competing interests., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The annual average concentration of fine particles (PM 2.5 ) in Taiwan has been decreasing yearly. However, ambient haze has not abated and visibility is still poor. This study proposes a method for quantifying the source apportionment of ambient haze from various constituents, namely measured PM 2.5 , moisture, and secondary organic aerosols (SOA, represented by the sum of measured O 3 and NO 2 levels). This study's model-based demisting technology integrated image haze extracting technology with air quality monitoring data. The images for haze extraction were from the instant cameras of the Taiwan Environmental Protection Agency's air quality monitoring stations (AQMSs). Results indicate that haze constituents with the product of light extinction and scene depth have very high correlation (R 2  ≥ 0.8452), which demonstrate that this quantification approach was successful. The contributions of ambient haze from various constituents had quarterly and regional variations in the eastern, northern, central, and southern regions of Taiwan, which are slightly, lowly, moderately, and heavily contaminated areas, respectively. Each area was assigned a selected representative AQMS to represent its ambient haze characteristics. Cases where the dominant contributors to haze were PM 2.5 , moisture, and SOA were studied, in addition to the event days of PM 2.5 and ozone. We detail the limits of this approach, especially with regard to the use of images. This approach can help administrators understand the composition of ambient haze to generate effective haze strategies and policies. Residents can use this method to determine the health effects of daily haze., (Copyright © 2020. Published by Elsevier Inc.)

This study integrated the results of photochemical grid modeling and assessment monitoring to quantify the impact of the offshore petrochemical industrial park (OPIP), with area of 26.03 km 2 , on ambient ozone in a coastal region of Taiwan. A highly repetitive ozone-spreading phenomenon in the adjacent OPIP area was observed, which shows that ozone spreading follows a clear cycle between offshore and inland areas during the prevailing periods of ozone events (≥ 120 ppb). The incremental ratio of ambient ozone for the OPIP on ozone event days during the southwest and northeast monsoons in 2011-2016 ranged from 1.05 to 1.25 (average = 1.15) and 1.04-1.27 (average = 1.17), respectively. Data from ten photochemical assessment monitoring stations surrounding the OPIP in 2016 showed that the ratio of monthly average concentrations of volatile organic compounds (VOCs) during the northeast monsoon to the southwest monsoon was approximately 1.5. The ratio of the monthly latent incremental amount of ozone to the total volatile organic amount in the same month during the northeast and southwest monsoons was in the ranges of approximately 0.84-0.97 and 1.01-1.12, respectively. Moreover, the latent incremental amount of ozone during the daytime was greater than that at night. The results indicate that the observed ozone concentration increases as the latent incremental amount of ozone or ambient VOCs decreases.

This study integrated estimated oxidation ratio of sulfur (SOR) and oxidation ratio of nitrogen (NOR) with source-receptor modeling results to identify the effects of terrain and monsoons on ambient aerosols in an urban area (north basin) and a rural area (south basin) of the Taichung Basin. The estimated results indicate that the conversion of sulfur mainly occurs in fine particles (PM₂.₅), whereas the conversion of nitrogen occurs in approximately equal quantities of PM₂.₅ and coarse particles (PM₂.₅-₁₀). The results show a direct relationship for PM₂.₅ between the modeling results with SOR and NOR. The high PM₂.₅ SOR, NOR, and secondary aerosol values all occurred in the upwind area during both monsoons; this shows that the photochemical reaction and the terrain effect on the pollutant transmission were significant in the basin. Additionally, the urban heat island effect on the urban area and the valley effect on the rural area were significant. The results show that secondary aerosol in PM₂.₅-₁₀ contributed approximately 10 % during both monsoons, and the difference in the contribution from secondary aerosol between both areas was small. Vehicle exhaust emissions and wind-borne dust were two crucial PM2.5-10 contributors during both monsoons; their average contributions in both areas were higher than 34 and 32 %, respectively.

The science parks have helped shape Taiwan as a high-tech island with a good reputation worldwide. But some complaints on air pollution from the science parks have recently risen. To better understand the environmental effects of volatile organic compounds (VOCs) emitted from various high-tech factories in a science park, this study uses a source-receptor approach to characterize the environmental effects of VOCs from control device exhaust in Taichung Science Park. The chemical mass balance model (CMB8.2) of field measurements of 30 stacks and ambient air at nine sites was used to identify the source and relative contribution of ambient VOCs. The exhaust gas of various pollution control devices was also sampled by drawing a stream of the gases from the exhaust duct at its sampling port. The VOC source profile of each control device exhaust was determined using a database of noncharacteristic compounds. Monthly ambient concentrations of 167 VOCs were divided into monsoon datasets to investigate the effect of monsoon conditions on the emission of VOCs in the science park. This study also suggests a method for determining the optimum source profile in source-receptor modeling, and identifies and analyzes the sources of ambient VOCs at nine sites during southwest and northeast monsoons. Results show a direct relationship between the relative contribution of each source and its control device efficiency. The proposed source-receptor approach can characterize the environmental effect of air pollutants from various factories and successfully assess the efficiency of various control devices.

A scale-free network model with surface and vertical field measurements was used to identify the connectivity distribution of the scale-free network behavior of ambient volatile organic compounds (VOCs). The results show that the carbon number (C(n)) with the total amount of C(n) compounds (P(C(n))) possesses an explicit relationship with the scale-free network behavior. The proportionate coefficient (α) and exponent (γ) of the scale-free network model with spatial and temporal variations are estimated and discussed. The analytical results demonstrate that although photochemical reactions cause the VOCs fraction variation, they do not alter the fraction of C(n) compounds observably. Therefore, the values of α and of γ did not vary with time, but with local regional characteristics. The results indicate that the influence of local VOCs emissions occurs at a height of 100 m, but becomes insufficient at a height of 300 m. Air mass mixing increases with greater height; thus, the influence of regional characteristics at a height of 700 m is low. Finally, a successful empirical model was established to evaluate the distribution of surface VOCs in various regions.