Effectiveness of different measures in reducing the daily number of moderate to severe cases of COVID-19

Objectives: Interventions for controlling COVID-19 can be classified into case-based (e.g., contact tracing and quarantining) and population-based (e.g., using masks and receiving vaccines) measures. The objective of pandemic control has now shifted from reducing the daily number of cases to reducing that of hospitalizations through vaccination. COVID-19 has started exhibiting flu-like characteristics. Therefore, in this study, we compared different measures in terms of their effectiveness in reducing the daily number of moderate to severe cases of COVID-19. Methods: The branching model developed by Hellewell (2020) was used for simulation. The epidemiological data of the Omicron variant and various hypothetical scenarios were analyzed. The outcome variable of our study was the daily number of hospitalizations under different measures and their combinations. Results: Population-based measures were more effective than case-based measures;however, their combination led to the best outcomes. If vaccination reduced the number of COVID-19-related hospitalizations, the focus was on increasing vaccine coverage to increase medical capacity rather than enhancing vaccine efficacy. Conclusions: While loosening case-based measures, the government must consider whether population-based measures can support this change. Furthermore, to reduce the daily number of moderate to severe cases of COVID-19, vaccine coverage, rather than vaccine efficacy, must be improved. (Taiwan J Public Health. 2023;42(1):32-41)

Assessing the robustness of COVID-19 vaccine efficacy trials: systematic review and meta-analysis, January 2023.

BackgroundVaccines play a crucial role in the response to COVID-19 and their efficacy is thus of great importance.AimTo assess the robustness of COVID-19 vaccine efficacy (VE) trial results using the fragility index (FI) and fragility quotient (FQ) methodology.MethodsWe conducted a Cochrane and PRISMA-compliant systematic review and meta-analysis of COVID-19 VE trials published worldwide until 22 January 2023. We calculated the FI and FQ for all included studies and assessed their associations with selected trial characteristics using Wilcoxon rank sum tests and Kruskal-Wallis H tests. Spearman correlation coefficients and scatter plots were used to quantify the strength of correlation of FIs and FQs with trial characteristics.ResultsOf 6,032 screened records, we included 40 trials with 54 primary outcomes, comprising 909,404 participants with a median sample size per outcome of 13,993 (interquartile range (IQR): 8,534-25,519). The median FI and FQ was 62 (IQR: 22-123) and 0.50% (IQR: 0.24-0.92), respectively. FIs were positively associated with sample size (p < 0.001), and FQs were positively associated with type of blinding (p = 0.023). The Spearman correlation coefficient for FI with sample size was moderately strong (0.607), and weakly positive for FI and FQ with VE (0.138 and 0.161, respectively).ConclusionsThis was the largest study on trial robustness to date. Robustness of COVID-19 VE trials increased with sample size and varied considerably across several other important trial characteristics. The FI and FQ are valuable complementary parameters for the interpretation of trial results and should be reported alongside established trial outcome measures.

Efficacy of BNT162b2 and CoronaVac in patients diagnosed with COVID-19.

This retrospective observational study is aimed to determine the efficacy of BNT162b2 (Pfizer-BioNTech) and CoronaVac (Sinovac) vaccines against symptomatic or severe disease in COVID-19-diagnosed patients. The secondary aim was to define the differences between vaccinated and un-vaccinated patients in terms of age, comorbidities and course of the disease, and to determine the survival rates. Of the 1463 PCR-positive patients, 55.3 % were vaccinated, and 44.7 % were unvaccinated. While 959 patients had mild-moderate symptoms, 504 patients had severe-critical symptoms and were treated in the intensive care unit. There was a statistically significant difference in the distribution of the type and doses of vaccines between the patient groups (p = 0.021). The rate of receiving 2 doses of Biontech was 18.9 % in the mild-moderate patient group but lower in the severe patient group (12.6 %). The rate of two doses of Sinovac and two doses of Biontech vaccine (four doses of vaccine) was 5 % in the mild-moderate patient group and 1.9 % in the severe patient group. The mortality rates were statistically significantly different (p < 0.001) between the patient groups: 65.3 % in the severe patient group and 1 % in the mild-moderate patient group. The multivariate model showed that the mortality risk of the unvaccinated patients was 1.5 times higher than the vaccinated ones (p = 0.042). In addition to being unvaccinated, advanced age, coronary artery disease (CAD), diabetes mellitus (DM), chronic obstructive pulmonary disease (COPD), chronic kidney disease (CKD), and obesity were found to be associated with higher mortality risk. Besides, the reduction in mortality rate was more evident in individuals vaccinated with at least 2 doses of the BNT162b2 (Pfizer-BioNTech) vaccine than in CoronaVac group.

The new generation of messenger RNA (mRNA) vaccines against influenza.

Today there are multiple types of flu vaccines. The emergence of nucleic acid technology used in vaccines against SARS-CoV-2 suggests its future application against this infection. Against influenza, two types of vaccines have been developed based on messenger RNA (mRNA): conventional or non-replicative and self-amplifying or replicative (auRNA), both included in lipid nanoparticles. Animal studies carried out with the former have shown their strong capacity to induce Th-1 antibodies and cellular immunity against influenza haemagglutinin (HA) with few side effects. Human trials have shown 87% seroconversion and 100% seroprotection. The auRNA vaccines have obtained similar results in animals but at a concentration 64 times lower than the conventional one. Vaccines based on mRNA platforms meet the WHO requirements for next generation influenza vaccines.

Current Status and Prospects of Vaccines based on DDS Technology

The development of DDS technology has contributed critically to the unprecedentedly rapid requirement for vaccines against COVID-19. LNP-based mRNA vaccines represent a subset of emerging DDS technology. Despite the groundbreaking nature of these vaccines, they are yet to be perfected and as such, new technologies are being developed to optimize these vaccines. This review will focus on exploring one of the modalities of recombinant protein vaccines and will introduce various findings on the enhancement of vaccine efficacy using antigen modification technologies, including VLPs and Fc-fusion proteins, and adjuvant improvements.Alternate :抄録COVID-19に対してかつてない速度でワクチンが普及した背景には、DDS技術の発展が必要不可欠であった。特に、mRNAワクチンにおける脂質ナノ粒子（LNP）の開発は、まさにDDS技術の結集といえよう。一方で、mRNAワクチンを含め、現状のさまざまなワクチンは多くの課題を有しており、より効果的かつ安全なワクチン開発に資する基盤技術の確立が世界的に待望されている。本稿では、ワクチンモダリティの1つである組換えタンパク質ワクチンに焦点を絞り、抗原改変技術からアジュバントの改良に至るまで、ワクチン開発基盤技術の最新知見について紹介する。

Vaccine development during a pandemic: General lessons for clinical trial design

The COVID-19 pandemic triggered an unprecedented research effort to develop vaccines and therapeutics. Urgency dictated that development and regulatory assessment were accelerated, while maintaining all standards for quality, safety and efficacy. To speed up evaluation the European Medicines Agency (EMA) implemented "rolling reviews” allowing developers to submit data for assessment as they became available.We discuss the clinical trial designs and the applied statistical approaches in vaccine efficacy trials, focusing on aspects such as multiple testing, interim and updated analyses, and reporting of results for the first four vaccines recommended for approval by the EMA. The fast accrual of COVID-19 cases in the clinical vaccine efficacy trials led to multiple data updates within a short time frame, which had consequences for the evaluation and interpretation of results. Key trial results are discussed in the light of these aspects. Notably, the aspects discussed did not affect the benefit/risk relationship in a meaningful way, which was clearly positive for all four vaccines.Assessment of the development and evaluation of the four vaccine trials during the pandemic has led to a proposal for standardised terminology for trials with multiple analyses and a recommendation to appropriately pre-plan the timing of primary and updated analyses. For the reporting of updated estimates of vaccine efficacy, we discuss how to best describe the uncertainty around estimates of vaccine efficacy (e.g., via confidence intervals). Finally, we briefly highlight the benefit of a comprehensive discussion on estimands for vaccine efficacy trials. [ FROM AUTHOR] Copyright of Statistics in Biopharmaceutical Research is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)

Temporal, age, and geographical variation in vaccine efficacy against infection by the Delta and Omicron variants in the community in France, December 2021 to March 2022.

OBJECTIVES: We aimed to quantify how the vaccine efficacy of BNT162b2, messenger RNA-1273, AD26.COV2-S, and ChAdOx1 nCoV-19 against detected infection by the SARS-CoV-2 Delta and Omicron variants varied by time since the last dose, vaccine scheme, age, and geographic areas. METHODS: We analyzed 3,261,749 community polymerase chain reaction tests conducted by private laboratories in France from December 2021 to March 2022 with a test-negative design comparing vaccinated to unvaccinated individuals. RESULTS: Efficacy against detected infection by Delta was 89% (95% confidence interval, 86-91%) at 2 weeks, down to 59% (56-61%) at 26 weeks and more after the second dose. Efficacy against Omicron was 48% (45-51%) at 2 weeks, down to 4% (2-5%) at 16 weeks after the second dose. A third dose temporarily restored efficacy. Efficacy against Omicron was lower in children and the elderly. Geographical variability in efficacy may reflect variability in the ratio of the number of contacts of vaccinated vs unvaccinated individuals. This ratio ranged from 0 to +50% across departments and correlated with the number of restaurants and bars per inhabitant (beta = 15.0 [0.75-29], P-value = 0.04), places that only vaccinated individuals could access in the study period. CONCLUSION: SARS-CoV-2 vaccines conferred low and transient protection against Omicron infection.

Efficacy of commercial live vaccines against QX-like infectious bronchitis virus in Japan.

Infectious bronchitis, an acute and highly contagious disease that affects chickens, is caused by the infectious bronchitis virus (IBV). The antigenic variant QX-like IBV was first reported in China in 1996 and is now endemic in many countries. Our previous study reported the first detection and isolation of QX-like IBVs in Japan and that they were genetically related to the recently detected strains in China and South Korea. The pathogenicity of 2 Japanese QX-like IBV strains (JP/ZK-B7/2020 and JP/ZK-B22/2020) was evaluated by inoculating specific pathogen-free (SPF) chickens with 102 to 106 median embryo infectious dose. Both strains caused clinical signs of respiratory symptoms, gross tracheal lesions, and moderate-to-severe suppression of tracheal ciliostasis. To evaluate the efficacy of commercial IBV live vaccines against the JP/ZK-B7/2020 strain, vaccinated SPF chickens were challenged with the JP/ZK-B7/2020 strain at 104 EID50 (median embryo infectious dose). Only the JP-Ⅲ vaccine provided high levels of protection (reduced suppression of tracheal ciliostasis and reduced viral loads in organs), whereas the Mass vaccine showed little protective effect. Virus neutralization test results and comparisons between IBV genotypes based on the S1 gene suggested that QX-like and JP-III genotypes were closely related. These results suggest that the JP-III IBV vaccine, which has relatively high S1 gene homology with QX-like IBVs, is effective against Japanese QX-like IBV strain.

NVX-CoV2373 vaccine efficacy against hospitalization: A post hoc analysis of the PREVENT-19 phase 3, randomized, placebo-controlled trial.

PREVENT-19, the pivotal phase 3 trial of the Novavax adjuvanted, recombinant spike protein COVID-19 vaccine (NVX-CoV2373), demonstrated that the vaccine was well tolerated and efficacious (vaccine efficacy, VE = 90%) for the prevention of symptomatic COVID-19. In the trial, participants were randomly assigned in a 2:1 ratio to receive 2 doses of NVX-CoV2373 or placebo 21 days apart. Throughout the study, the predominant SARS-CoV-2 variant was alpha, but additional variants were in circulation (i.e., beta, gamma, epsilon, and iota). VE among the per-protocol efficacy analysis population was calculated according to pre-specified disease severity (mild, moderate, or severe) criteria, but the impact on the risk of COVID-19-associated hospitalization was not specifically investigated. During this analysis period (January 25, 2021, to April 30, 2021 [95 days]), 4 hospitalizations occurred among the 77 events analyzed for the primary endpoint using the per-protocol population, 0 among vaccine recipients and 4 among placebo recipients, yielding a post hoc VE against hospitalization of 100% (95% CI: 28.8, 100). Among an expanded efficacy population, also identified post hoc, which included COVID-19-associated hospitalizations without a requirement for diagnostic polymerase chain reaction testing performed at the study central laboratory, 12 total hospitalizations were identified, 0 among vaccine recipients and 12 among placebo recipients, yielding a post hoc VE against hospitalization of 100% (95% CI: 83.1, 100). These additional data from the PREVENT-19 trial provide relevant public health information concerning the attributes of NVX-CoV2373.

Impact of vaccination on the entire population and dose-response relation of COVID-19.

Objective: The objective of this study is to develop a mathematical model for the COVID-19 pandemic including vaccination, the transmissibility of the virus-pathogen dose-response relationship, vaccine efficiency, and vaccination rate. Methods: The Runge-Kutta (RK-45) method was applied to solve the proposed model with MATLAB code and the calculated results show the dynamics of the individuals in each compartment. The data of total death due to the COVID-19 pandemic in the case of the USA were collected from GitHub and the re-use of this data needs no ethical clearance. The control reproduction number was used to assess the dose-response relationship and critical vaccination coverage. Results: We have calculated the probability of infection and the infection risk against the different exposure doses and the virus copies, respectively. The results show that the probability of infection increases with the increasing exposure dose for certain virus copies and the risk of infection decreases with the increasing of virus copies for a certain exposure dose. The results also show that the critical vaccination coverage demands increase with an increase in transmission rate and decrease with increasing vaccine efficacy. Conclusions: It was seen that the critical vaccination coverage corresponding to an increased transmission rate rise sharply in the beginning and then reached a threshold. Moreover, the real data of the total death cases in the USA were compared with the fitted curved of the model which validated the proposed model. Vaccination against COVID-19 is essential to control the pandemic, and achieving high vaccine uptake in the population can reduce the pandemic as fast as possible.

Objetivo: El objetivo de este estudio es desarrollar un modelo matemático para la pandemia de COVID-19 que incluya la vacunación, la transmisibilidad de la relación dosis-respuesta virus-patógeno, la eficacia de la vacuna y la tasa de vacunación. Métodos: Se aplicó el método de Runge-Kutta (RK-45) para resolver el modelo propuesto con código MATLAB y los resultados calculados muestran la dinámica de los individuos en cada compartimento. Los datos de muerte total por la pandemia de COVID-19 en el caso de EE. UU. se recopilaron de GitHub y la reutilización de estos datos no necesita autorización ética. El número de reproducción de control se utilizó para evaluar la relación dosis-respuesta y la cobertura de vacunación crítica. Resultados: Hemos calculado la probabilidad de infección y el riesgo de infección frente a las diferentes dosis de exposición y las copias del virus, respectivamente. Los resultados muestran que la probabilidad de infección aumenta con el aumento de la dosis de exposición para ciertas copias del virus y el riesgo de infección disminuye con el aumento de las copias del virus para una determinada dosis de exposición. Los resultados también muestran que las demandas críticas de cobertura de vacunación aumentan con el aumento de la tasa de transmisión y disminuyen con el aumento de la eficacia de la vacuna. Conclusiones: Se observó que las coberturas críticas de vacunación correspondientes a una mayor tasa de transmisión aumentaron bruscamente al principio y luego alcanzaron un umbral. Además, se compararon los datos reales del total de casos de muerte en EE. UU. con la curva ajustada del modelo que validó el modelo propuesto. La vacunación contra el COVID-19 es fundamental para controlar la pandemia, y lograr una alta captación de vacunas en la población puede reducir la pandemia lo más rápido posible.

Coverage of Coronavirus Disease-2019 (COVID-19) Booster Dose (Precautionary) in the Adult Population: An Online Survey.

Background The coronavirus disease-2019 (COVID-19) pandemic devastated public health worldwide, including India. COVID-19 vaccines and their boosters are life-saving developments that have helped prevent and control the spread of COVID-19. We conducted this study to assess the coverage of the booster dose in an Indian population (the third dose of the COVID-19 vaccine in India is referred to as the booster or precautionary dose), record the reasons for not taking the booster dose, and determine the effectiveness of the booster. The levels of adherence to COVID-19 precautionary behavior was also assessed.  Methods We conducted a descriptive, cross-sectional study using convenient sampling via an online survey of 550 respondents older than 18 in the second quarter of 2022. The respondents were distributed among 18 states and union territories in India. The data were analyzed as simple proportions and percentages. Results Of the 550 respondents, 152 (27.6%) received the booster dose, indicating low coverage. A small percentage of respondents (7.2%) reported suffering from COVID-19 following the booster, of whom 91% were medical professionals. The most common reported reason for not taking the vaccine was that the respondents were not yet due for their dose (48.1%). The time between the second dose of the COVID-19 vaccine and the booster had no impact on infection rates. Men were less likely to adhere to COVID-19 precautionary behavior than women, despite similar vaccination rates. Conclusion The COVID-19 vaccine booster had a low acceptance in our study population, with roughly one-quarter of the population receiving the booster. The booster dose has been influential in the prevention of COVID-19. Most respondents followed behavioral safety measures despite the decline of active cases of COVID-19 in India following the Omicron wave. Our results indicate a need to strengthen public strategies to affect behavioral changes, such as improving India's Behavior Change Communication program to ensure adequate booster dose coverage.

[The new generation of messenger RNA (mRNA) vaccines against influenza]. / La nueva generación de vacunas de ARN mensajero (ARNm) frente a la gripe.

Today there are multiple types of flu vaccines. The emergence of nucleic acid technology used in vaccines against SARS-CoV-2 suggests its future application against this infection. Against influenza, two types of vaccines have been developed based on messenger RNA (mRNA): conventional or non-replicative and self-amplifying or replicative (auRNA), both included in lipid nanoparticles. Animal studies carried out with the former have shown their strong capacity to induce Th-1 antibodies and cellular immunity against influenza haemagglutinin (HA) with few side effects. Human trials have shown 87% seroconversion and 100% seroprotection. The auRNA vaccines have obtained similar results in animals but at a concentration 64 times lower than the conventional one. Vaccines based on mRNA platforms meet the WHO requirements for next generation influenza vaccines.

Dietary intervention with functional foods modulating gut microbiota for improving the efficacy of COVID-19 vaccines.

Dysbiosis of the gut microbiota with aging contributes to a reduction in important cross-feeding bacterial reactions in the gut and immunosenescence, which could contribute to a decrease in vaccine efficacy. Fever, cough, and fatigue are the main signs of coronavirus disease 2019 (COVID-19); however, some patients with COVID-19 present with gastrointestinal symptoms. COVID-19 vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is one of the best measures to reduce SARS-CoV-2 infection rates and the severity of COVID-19. The immunogenicity of COVID-19 vaccines is influenced by the composition of the gut microbiota, and the immune response to COVID-19 vaccines decreases with age. In this review, we discuss gut microbiota dysbiosis and immunosenescence in the older adults, the role of gut microbiota in improving the efficacy of COVID-19 vaccines, and dietary interventions to improve the efficacy of COVID-19 vaccines in the older adults.

Longitudinal analysis of anti-SARS-CoV-2 neutralizing antibody (NAb) titers in vaccinees using a novel giant magnetoresistive (GMR) assay.

The COVID-19 pandemic has highlighted the need to monitor important correlates of immunity on a population-wide level. To this end, we have developed a competitive assay to assess neutralizing antibody (NAb) titer on the giant magnetoresistive (GMR) biosensor platform. We compared the clinical performance of our biosensor with established techniques such as Ortho's VITROS Anti-SARS-CoV-2 IgG Quantitative Antibody test. Results obtained between the VITROS test and the GMR assay showed correlation (r = -0.93). We then validated the assay with patient plasma samples that had been tested using focus reduction neutralization testing (FRNT). The results obtained from our GMR assay exhibit a previously identified trend of increased NAb titers 2 weeks post-vaccination. We further evaluated NAb titers 6 months post-vaccination and observed waning neutralizing antibody titers over that time in vaccinated patients. In addition, we calibrated our assay to an arbitrary unit (IU/mL) using World Health Organization (WHO) reference plasma provided by the National Institute of Biological Standards and Control (NIBSC). Our biosensor provides highly specific and sensitive results in serum and plasma with analytical, clinical, and point-of-care (POC) applications due to quick turnaround times on samples and the cost-effectiveness of the platform.

A population-based paediatric Covid-19 vaccination progress and outcomes: The Malta case.

Background: Covid-19 is still pandemic with population vaccination, including among children, remaining the mainstay for hastening the exit from the pandemic. The article provides an insight in Malta's national paediatric vaccination modus operandi, vaccination uptake, and epidemiological trends while exploring geographical social inequalities among the ≤ 15 years cohort up till end of August 2022. Methods: The Vaccination Coordination Unit in Malta's only regional hospital provided an account of the strategic roll-out along with anonymised cumulative vaccination doses by age band and district. Descriptive and multivariant logistic regression analyses were performed. Results: By mid-August 2022, 44.18% of the under 15's population had received at least 1 vaccine dose. A bi-directional relationship was observed between increased cumulative vaccination and reported Covid-19 cases until early 2022. Central vaccination hubs were set up with invitation letters and SMSs sent to parents. Children residing in the Southern Harbour district (OR: 0.42, P < 0.01) had the highest full vaccination uptake (46.66%) as opposed to the Gozo district (lowest at 27.23%; OR: 0.3, P = 0.01). Conclusion: Successful paediatric vaccination is not only dependent on easily accessible vaccination but also on vaccine effectiveness against variants, as well as population characteristics, with potential geographical social inequalities hindering uptake.

Evaluation of mortality risk after COVID-19 vaccination, Utah 2021.

INTRODUCTION: In order to evaluate trends in death after COVID-19 vaccination we analyzed the timing of death relative to vaccination date and the causes of death in vaccinated Utahns in 2021. METHODS: We matched people in the Utah immunization registry with documented COVID-19 vaccinations between December 18, 2020 and December 31, 2021 to Utah's 2021 vital statistics death records. Vaccinated people were categorized as having one, two, or ≥ three COVID-19 vaccine doses in a time-updated metric. We examined crude mortality rates by dosing groups in two-week intervals for all deaths, and by COVID-19 versus non-COVID-19 causes, within the 44 weeks following receipt of the most recent vaccine. RESULTS: We identified 2,072,908 individuals who received at least one dose of COVID-19 vaccine of whom 10,997 died in 2021. Only 17.5 % of the total vaccinated population was age 65+, while 80.9 % of those who died were over 65. In the four weeks following the first or second vaccination, all-cause mortality was low and then stabilized for the remainder of the evaluation period at a bi-weekly average of 33.0 and 39.0 deaths/100,000 people for one and two doses, respectively. Typical seasonal variation in death was observed among those with two doses. Small sample size precluded analysis of those with ≥ three doses, but trends were similar. CONCLUSIONS: Mortality rates in the 44 weeks following the COVID-19 vaccination did not show trends suggesting an increase in mortality related to COVID-19 vaccination, reinforcing the safety of COVID-19 vaccines. This represents an accessible approach for local evaluation.

COVID-19 Vaccine Effectiveness Against Omicron Infection and Hospitalization

OBJECTIVES: This study aimed to provide real-world evidence on coronavirus disease 2019 vaccine effectiveness (VE) against symptomatic infection and severe outcomes caused by Omicron in children aged 5 to 11 years. METHODS: We used the test-negative study design and linked provincial databases to estimate BNT162b2 vaccine effectiveness against symptomatic infection and severe outcomes caused by Omicron in children aged 5 to 11 years between January 2 and August 27, 2022 in Ontario. We used multivariable logistic regression to estimate VE by time since the latest dose, compared with unvaccinated children, and we evaluated VE by dosing interval. RESULTS: We included 6284 test-positive cases and 8389 test-negative controls. VE against symptomatic infection declined from 24% (95% confidence interval [CI], 8% to 36%) 14 to 29 days after a first dose and 66% (95% CI, 60% to 71%) 7 to 29 days after 2 doses. VE was higher for children with dosing intervals of ≥56 days (57% [95% CI, 51% to 62%]) than 15 to 27 days (12% [95% CI, - 11% to 30%]) and 28 to 41 days (38% [95% CI, 28% to 47%]), but appeared to wane over time for all dosing interval groups. VE against severe outcomes was 94% (95% CI, 57% to 99%) 7 to 29 days after 2 doses and declined to 57% (95%CI, -20% to 85%) after ≥120 days. CONCLUSIONS: In children aged 5 to 11 years, 2 doses of BNT162b2 provide moderate protection against symptomatic Omicron infection within 4 months of vaccination and good protection against severe outcomes. Protection wanes more rapidly for infection than severe outcomes. Overall, longer dosing intervals confer higher protection against symptomatic infection, however protection decreases and becomes similar to shorter dosing interval starting 90 days after vaccination.

The effect of social media communication on intention to vaccinate against COVID-19: A relationship mediated by perceptions of vaccine efficacy and safety

Although previous literature has found significant effects of social media communication (SMC) on intention to vaccinate, the effect of the sources of SMC has not been explored. To fill this gap, this study investigates a) the effects of official sources and user-generated SMC on intention to vaccinate against COVID-19, and b) the mediating effects of perceived vaccine efficacy, safety, and risk perception on the relationship between SMC and intention to vaccinate against COVID-19. Online survey data (n = 428) was analysed using structural equation modelling (SEM). Results revealed that official sources SMC is positively associated with vaccine intention while user-generated SMC had no significant association. Mediation analysis revealed a partial mediation effect of perceived vaccine efficacy and safety in the relationship between official source SMC and intention to vaccinate against COVID-19, while a full mediation effect of perceived vaccine efficacy and safety was found between user-generated SMC and intention to vaccinate against COVID-19. The mediating effect of perceived risk was not found. © 2023 Informa UK Limited, trading as Taylor & Francis Group.

COVID-19 Vaccines: Overview, Efficacy, Safety and Challenges

The rapid and extraordinary development and deployment of Coronavirus disease 2019 (COVID-19) vaccines worldwide represent an unprecedented achievement in the history of vaccine development. This chapter provides an overview of COVID-19 vaccine strategies, platforms, clinical trials, and regulatory frameworks. Vaccine safety, efficacy, herd immunity, and severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) variants are also discussed. Real world challenges confronted include the ethics of vaccine allocation, vaccine nationalism, vaccine hesitancy, and vaccine passports. © 2023 by World Scientific Publishing Co. Pte. Ltd.

The Contagious Nature of SARS-CoV-2 Omicron Variant and Vaccine Efficacy

Since the first coronavirus disease-19 (COVID-19) outbreak, variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have continued to dominate the global population. The repeated waves of emerging variants, each replacing the previous one with a greater rate of transmissibility and mutations, are the primary cause of the global pandemic. Public health concerns dramatically rose when a highly mutated variant, omicron (B.1.1.529) emerged in late 2021. Omicron has more than 50 mutations, and over 30 mutations are in their spike protein that contributes to the virologic characteristics of the variant. Omicron is more contagious than previously reported SARS-CoV-2 strains and can re-infect people who have already contracted other SARS-CoV-2 infections. The variant has acquired a unique immune escape mechanism against monoclonal antibodies and vaccines. Currently, there are no specific therapeutic drugs or vaccines available to prevent omicron infection and sub lineages emergence. The review was designed to search the recent research or literature papers and compile the most pertinent data on the virologic characteristics of the variant of concern. The study reviewed and discussed the present prevalence, infectivity, dominance, immune evasion, therapeutic options, vaccine efficacy, and the future prospect of the omicron variant. Omicron variant has become a global public health concern due to the emergence of highly mutated sub lineages. Developing variant-specific therapeutic drugs or vaccines is desirable to prevent the spread of these contagious variants globally. © 2022, The Running Line. All rights reserved.