Incubation-period estimates of Omicron (BA.1) variant from Taiwan, December 2021-January 2022, and its comparison to other SARS-CoV-2 variants: a statistical modeling, systematic search and meta-analysis (preprint)

Background: The ongoing COVID-19 pandemic has seen several variants of concern, including the Omicron (BA.1) variant which emerged in October 2021. Accurately estimating the incubation period of these variants is crucial for predicting disease spread and formulating effective public health strategies. However, existing estimates often conflict because of biases arising from the dynamic nature of epidemic growth and selective inclusion of cases. This study aims to accurately estimate of the Omicron (BA.1) variant incubation period based on data from Taiwan, where disease incidence remained low and contact tracing was comprehensive during the first months of the Omicron outbreak. Methods: We reviewed 100 contact-tracing records for cases of the Omicron BA.1 variant reported between December 2021 and January 2022, and found enough information to analyze 70 of these. The incubation period distribution was estimated by fitting data on exposure and symptom onset within a Bayesian mixture model using gamma, Weibull, and lognormal distributions as candidates. Additionally, a systematic literature search was conducted to accumulate data for estimates of the incubation period for Omicron (BA.1/2, BA.4/5) subvariants, which was then used for meta-analysis and comparison. Results: The mean incubation period was estimated at 3.5 days (95% credible interval: 3.1-4.0 days), with no clear differences when stratified by vaccination status or age. This estimate aligns closely with the pooled mean of 3.4 days (3.0-3.8 days) obtained from a meta-analysis of other published studies on Omicron subvariants. Conclusions: The relatively shorter incubation period of the Omicron variant, as compared to previous SARS-CoV2 variants, implies its potential for rapid spread but also opens the possibility for individuals to voluntarily adopt shorter, more resource-efficient quarantine periods. Continual updates to incubation period estimates, utilizing data from comprehensive contact tracing, are crucial for effectively guiding these voluntary actions and adjusting high socio-economic cost interventions.

Safety and immunogenicity of homologous versus heterologous booster dose with AZD1222, mRNA-1273, or MVC-COV1901 SARS-CoV-2 vaccines in adults: An observer-blinded, multi-center, phase 2 randomized trial.

OBJECTIVES: To report the safety and immunogenicity profile of a protein subunit vaccine (MVC-COV1901) compared to AZD1222 and mRNA-1273 when given as a third (booster) dose to individuals who have completed different primary vaccine regimens. METHODS: Individuals were classified according to their primary vaccine regimens, including two-dose MVC-COV1901, AZD1222, or mRNA-1273. A third dose of either half-dose MVC-COV1901, full-dose MVC-COV1901, standard-dose AZD1222, half-dose mRNA-1273 was administered in a 1:1:1:1 treatment ratio to individuals with an interval range of 84-365 days after the second dose. Endpoints included safety, humoral immunogenicity, and cell-mediated immune response on trial days 15 and 29. Exploratory endpoint included testing against variants of concern (Omicron). RESULTS: Overall, 803 participants were randomized and boosted - 201 received half-dose MVC-COV1901, 196 received full-dose MVC-COV1901, 203 received AZD1222, and 203 received half-dose mRNA-1273. Reactogenicity was mild to moderate, and less in the MVC-COV1901 booster group. Heterologous boosting provided the best immunogenic response. Boosting with mRNA-1273 in MVC-COV1901 primed individuals induced the highest antibody titers, even against Omicron, and cell-mediated immune response. CONCLUSIONS: Overall, MVC-COV1901 as a booster showed the best safety profiles. MVC-COV1901 as a primary series, with either homologous or heterologous booster, elicited the highest immunogenic response. CLINICALTRIALS: gov registration NCT05197153.

A study of COVID-19 vaccination in the US and Asia: The role of media, personal experiences, and risk perceptions

The COVID-19 pandemic presents an opportunity to assess the relationship between personal experiences and vaccine decision-making. The aim of this study was to examine the associations between experiences with COVID-19 and COVID-19 vaccination status. We administered 28 repeated cross-sectional, online surveys between June 2020 and June 2021 in the US and Asia. The main exposure was media showing COVID-19 cases, and we distinguished those with no such experience, those seeing a not severe case of disease, and those seeing a severe case of disease. Logistic regression models estimated the association between experience and acceptance of a hypothetical COVID-19 vaccine (pre-rollout) or actual vaccination (post-rollout). We explored perceived susceptibility as a potential mediator. Intent to vaccinate was lowest in the US and Taiwan, and highest in India, Indonesia, and China. Across all countries, seeing a severe case of COVID-19 in the media was associated with 1.72 times higher odds of vaccination intent in 2020 (95% CI: 1.46, 2.02) and 2.13 times higher odds of vaccination in 2021 (95% CI: 1.70, 2.67), compared to those not seeing a case or a less severe case. Perceived susceptibility was estimated to mediate 25% of the relationship with hypothetical vaccination (95% CI: 18%, 31%, P<0.0001), and 16% of the relationship with actual vaccination 16% (95% CI: 12%, 19%, P<0.0001). Seriousness of experiences could relate to intention to vaccinate against COVID-19. Media exposures are a modifiable experience, and this study highlights how this experience can relate to risk perceptions and eventual vaccination, across a variety of countries where the course of the pandemic differed.

Potential lessons from the Taiwan and New Zealand health responses to the COVID-19 pandemic.

Approaches to preventing or mitigating the impact of the COVID-19 pandemic have varied markedly between nations. We examined the approach up to August 2020 taken by two jurisdictions which had successfully eliminated COVID-19 by this time: Taiwan and New Zealand. Taiwan reported a lower COVID-19 incidence rate (20.7 cases per million) compared with NZ (278.0 per million). Extensive public health infrastructure established in Taiwan pre-COVID-19 enabled a fast coordinated response, particularly in the domains of early screening, effective methods for isolation/quarantine, digital technologies for identifying potential cases and mass mask use. This timely and vigorous response allowed Taiwan to avoid the national lockdown used by New Zealand. Many of Taiwan's pandemic control components could potentially be adopted by other jurisdictions.

An evaluation of the safety and immunogenicity of MVC-COV1901: Results of an interim analysis of a phase III, parallel group, randomized, double-blind, active-controlled immunobridging study in Paraguay.

BACKGROUND: Data from previous studies of the MVC-COV1901 vaccine, a subunit vaccine against SARS-CoV-2 based on the stable prefusion spike protein (S-2P) adjuvanted with CpG 1018 adjuvant and aluminum hydroxide, suggest that the vaccine is generally safe and elicits a good immune response in healthy adults and adolescents. By comparing with AZD1222, this study adds to the findings from previous trials and further evaluates the breadth of protection offered by MVC-COV1901. METHODS: In this phase 3, parallel group, randomized, double-blind, active-controlled trial conducted in 2 sites in Paraguay, we assigned adults aged 18-91 years in a 1:1 ratio to receive intramuscular doses of MVC-COV1901 or AZD1222 administered as scheduled in the clinical trial. Serum samples were collected on the day of vaccination and 14 days after the second dose. Primary and secondary safety and immunogenicity endpoints were assessed. In addition, other outcomes investigated were cross-reactive immunity against the Omicron strain and the induction of IgG subclasses. RESULTS: A total of 1,030 participants underwent randomization. Safety data was derived from this set while primary immunogenicity data involved a per-protocol immunogenicity (PPI) subset including 225 participants. Among the participants, 58% are seropositive at baseline. When compared against AZD1222, MVC-COV1901 exhibited superiority in terms of neutralizing antibody titers and non-inferiority in terms of seroconversion rates. Reactogenicity was generally mild and no serious adverse event was attributable to MVC-COV1901. Both vaccines have a Th1-biased response predominated by the production of IgG1 and IgG3 subclasses. Omicron-neutralizing titers were 44.5 times lower compared to wildtype-neutralizing titers among seronegative individuals at baseline. This fold-reduction was 3.0 times among the seropositive. CONCLUSION: Safety and immunogenicity data of MVC-COV1901 from the study in Paraguay confirm previous results. The previous infection coupled with vaccination of this vaccine may offer protection against the Omicron strain though its durability is still unknown.

Safety and immunogenicity of SARS-CoV-2 vaccine MVC-COV1901 in Taiwanese adolescents: a randomized phase 2 trial.

Adolescents and children play an important role in SARS-CoV-2 transmission and epidemiology. MVC-COV1901 is a subunit SARS-CoV-2 vaccine based on stabilized spike protein adjuvanted with CpG 1018 and aluminum hydroxide that has received emergency use approval (EUA) for adults in Taiwan. In this study, we have investigated the safety and immunogenicity of two doses of MVC-COV1901 in adolescents. Healthy adolescents from the age of 12-17 years were randomly assigned to receive two intramuscular doses of either MVC-COV1901 or placebo at 28 days apart. Adverse events were mostly mild and were similar in MVC-COV1901 and placebo groups, with the most commonly reported adverse events being pain/tenderness and malaise/fatigue. All immunogenicity endpoints in the adolescent group were non-inferior to the endpoints seen in the young adult and placebo groups. The results here advocate the use of MVC-COV1901 in adolescents in the ongoing efforts to control the pandemic.ClinicalTrials.gov registration: NCT04951388.

Early Prompt Response to COVID-19 in Taiwan: Comprehensive surveillance, decisive border control, and information technology support.

Since the COVID-19 outbreak was detected in Wuhan in December 2019 by the event-based surveillance of Taiwan Centers for Disease Control, Taiwan has been aligning risk management to policy planning with the assistance of comprehensive surveillance and regular rapid risk assessments. Taiwan Central Epidemic Command Center (CECC) promptly initiated stepwise border control for major cities and provinces in China, European and American countries, and eventually expanded it to the whole world in March 2020. With stringent quarantine measures, the early response not only successfully blocked the first wave of imported cases, but also slowed down subsequent large local outbreaks. Digital technologies including digital fencing and government database linkage were adopted to facilitate the application of public health interventions and data collection. The experience of Taiwan's prompt and comprehensive response at the early stage may contribute to the preparedness for the next disease X outbreak.

Transmission Dynamics and Effectiveness of Control Measures during COVID-19 Surge, Taiwan, April-August 2021.

An unprecedented surge of COVID-19 cases in Taiwan in May 2021 led the government to implement strict nationwide control measures beginning May 15. During the surge, the government was able to bring the epidemic under control without a complete lockdown despite the cumulative case count reaching >14,400 and >780 deaths. We investigated the effectiveness of the public health and social measures instituted by the Taiwan government by quantifying the change in the effective reproduction number, which is a summary measure of the ability of the pathogen to spread through the population. The control measures that were instituted reduced the effective reproduction number from 2.0-3.3 to 0.6-0.7. This decrease was correlated with changes in mobility patterns in Taiwan, demonstrating that public compliance, active case finding, and contact tracing were effective measures in preventing further spread of the disease.

Safety and immunogenicity of SARS-CoV-2 vaccine MVC-COV1901 in Taiwanese adolescents: A double-blind, randomized, placebo-controlled phase 2 trial (preprint)

Adolescents and children play important role in SARS-CoV-2 transmission and epidemiology. MVC-COV1901 is a subunit SARS-CoV-2 vaccine based on stabilized spike protein adjuvanted with CpG 1018 and aluminum hydroxide that has been approved for use in adults in Taiwan. In this study, we have investigated the safety and immunogenicity of two doses of MVC-COV1901 in adolescents. Healthy adolescents from age of 12 to 17 years were randomly assigned to receive two intramuscular doses of either MVC-COV1901 or placebo at 28 days apart. Adverse events were mostly mild and were similar in MVC-COV1901 and placebo groups with the most commonly reported adverse events being pain/tenderness and malaise/fatigue. All immunogenicity endpoints in the adolescent group were non-inferior to the endpoints seen in the young adult and placebo groups. The results here advocate the use of MVC-COV1901 in adolescents in the ongoing efforts to control the pandemic. ClinicalTrials.gov registration NCT04951388.

An Evaluation of the Safety and Immunogenicity of MVC-COV1901: Results of an interim analysis of a phase III, parallel group, randomized, double-blind, active-controlled study (preprint)

Background: Data from previous studies of the MVC-COV1901 vaccine, a subunit vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) based on the stable prefusion spike protein (S-2P) adjuvanted with CpG 1018 adjuvant and aluminum hydroxide, suggest that the vaccine is generally safe and elicits a good immune response in healthy adult and adolescents. By comparing with the active control, AZD1222, this study adds to the findings from previous trials and further evaluates the breadth of protection offered by MVC-COV1901. Methods: In this phase 3, parallel group, randomized, double-blind, active-controlled trial conducted in 2 sites in Paraguay, we assigned adults aged 18 to 91 years in a 1:1 ratio to receive intramuscular doses of MVC-COV1901 or AZD1222 administered as scheduled in the clinical trial. Serum samples were collected on the day of vaccination, Day 1, and 14 days after the second dose (Day 43 after first dose). Primary and secondary safety and immunogenicity endpoints were assessed. In addition, other outcomes investigated were cross-reactive immunity against the Omicron strain and non-neutralizing antibody immune effector mechanisms particularly the induction of IgG subclasses. Results: A total of 1,030 participants underwent randomization. Safety data was derived from this set while primary immunogenicity data involved a per-protocol immunogenicity (PPI) subset including 225 participants. Among the participants, 58% are seropositive at baseline. The mean age was 32.1 years and approximately 60% were males. An estimated 35.3% of participants had coexisiting medical conditions. When compared against AZD1222, MVC-COV1901 exhibited superiority in terms of neutralizing antibody titers geometric mean titer ratio (GMTR) [GMTR seronegative: 4.8 (95% CI 3.0-7.7); GMTR seropositive: 1.7 (95% CI 1.2-2.2)] and non-inferiority in terms of seroconversion rates. Reactogenicity was generally mild. The incidence of serious adverse events was low in both groups. Both vaccines have a Th1-biased response that is predominated by the production of IgG1 and IgG3 subclasses-with MVC-COV1901 exhibiting a stronger antibody response. In the pseudovirus assay, Omicron-neutralizing titers were 44.5 times lower compared to wildtype-neutralizing titers among seronegative individuals at baseline. This fold-reduction was reduced to 3.0 times among the seropositive. Conclusion: Safety and immunogenicity data presented here demonstrate the safe and robust immunogenicity from MVC-COV1901. Previous infection coupled with vaccination of this vaccine may offer protection against the Omicron strain though its durability is still unknown.

Durability and Immunogenicity of Neutralizing Antibodies Response Against Omicron Variants After Three Doses of Subunit SARS-CoV-2 Vaccine MVC-COV1901: An Extension to an Open-Label, Dose-Escalation Phase 1 Study.

INTRODUCTION: MVC-COV1901 is a protein subunit COVID-19 vaccine based on the stable prefusion spike protein S-2P adjuvanted with CpG 1018 and aluminum hydroxide. Interim results of a phase 2 clinical trial demonstrated favorable safety profile and immunogenicity and the vaccine has been authorized for use in Taiwan. However, waning antibody levels after immunization and variants of concern (VoC) could negatively impact vaccine-induced neutralization of virus. In this extension to the phase 1 clinical study we investigated a three-dose regimen of MVC-COV1901 for durability of antibody levels and virus neutralization capacity, including neutralization of the Omicron variant. METHODS: Forty-five healthy adults from 20 to 49 years of age were divided into three groups of 15 participants receiving two doses of either low dose (LD), medium dose (MD), or high dose (HD) of MVC-COV1901. Six months after the second dose (day 209), a third MD dose of MVC-COV1901 was administered to the LD and MD groups and a HD dose was given to the HD group. Safety was followed for up to 28 days after the booster dose by monitoring incidences of adverse events (AE). Immunogenicity and antibody persistence for up to 6 months after the booster dose were assessed by neutralizing assay with the wild-type (Wuhan) SARS-CoV-2 virus. To examine the immunogenicity of booster dose against variants, neutralizing assays were carried out with the Alpha, Beta, and Delta variant viruses and the Omicron variant pseudovirus using samples from 4 weeks after the booster dose. RESULTS: Adverse reactions after the booster dose were mostly mild and comparable to that of the first two doses. Compared to day 209, neutralizing antibodies were increased by 10.3-28.9 times at 4 weeks after the booster. During the 6-month follow-up after the booster, the rate of decline of neutralizing antibody level was much less than that after the second dose. Three doses of MVC-COV1901 also improved antibody-mediated neutralization of Alpha, Beta, and Delta variants as well as the Omicron variant pseudovirus. CONCLUSION: Our data showed increased persistence of neutralizing antibodies and enhancement of immunogenicity against VoCs offered after a third dose of MVC-COV1901. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT04487210.

Safety and immunogenicity of SARS-CoV-2 vaccine MVC-COV1901 in adolescents in Taiwan: A double-blind, randomized, placebo-controlled phase 2 trial (preprint)

Background: MVC-COV1901 is a subunit SARS-CoV-2 vaccine based on the prefusion spike protein S-2P and adjuvanted with CpG 1018 and aluminum hydroxide. Although MVC-COV1901 has been licensed for emergency use for adults in Taiwan, the safety and immunogenicity of MVC-COV1901 in adolescents remained unknown. As young people play an important role in SARS-CoV-2 transmission and epidemiology, a vaccine approved for adolescents and eventually, children, will be important in mitigating the COVID-19 pandemic. Methods: This study is a prospective, double-blind, multi-center phase 2 trial evaluating the safety, tolerability and immunogenicity of two doses of the SARS-CoV-2 vaccine MVC-COV1901 in adolescents. Healthy adolescents from age of 12 to 17 years were recruited and randomly assigned (6:1) to receive two intramuscular doses of either MVC-COV1901 or placebo at 28 days apart. The primary outcomes were safety and immunogenicity from the day of first vaccination (Day 1) to 28 days after the second vaccination (Day 57), and immunogenicity of MVC COV1901 in adolescents as compared to young adult vaccinees in terms of neutralizing antibody titers and seroconversion rate. The secondary outcomes were safety and immunogenicity of MVC-COV1901 as compared to placebo in adolescents in terms of immunoglobulin titers and neutralizing antibody titers over the study period. Results: Between July 21, 2021 and December 22, 2021, a total of 399 adolescent participants were included for safety evaluation after enrollment to receive at least one dose of either MVC-COV1901 (N=341) or placebo (N=58). Of these, 334 and 46 participants went on to receive two doses of either MVC-COV1901 or placebo, respectively, and were included in the per protocol set (PPS) for immunogenicity analysis. Adverse events were mostly mild and were similar in MVC-COV1901 and placebo groups. The most commonly reported adverse events were pain/tenderness and malaise/fatigue. All immunogenicity endpoints in the adolescent group were non-inferior to the endpoints seen in the young adult and placebo groups. Conclusions: The safety and immunogenicity data presented here showed that MVC-COV1901 has similar safety profile and non-inferior immunogenicity in adolescents compared to young adults.

A Global Study of COVID-19 Vaccination Intentions: The Role of Personal Experiences and Risk Perceptions (preprint)

Background: The COVID-19 pandemic presents an opportunity to assess the impact of personal experiences on vaccine decision-making. The aim of this study was to examine the associations between experiences with COVID-19 and intention to vaccinate against COVID-19. Methods We administered 28 repeated cross-sectional, online surveys between June 2020 and June 2021 in the US and Asia. The main exposures were three types of experiences: COVID-19 diagnosis, knowing a friend/family member with COVID-19, and exposures to media containing COVID-19 patients. A series of logistic regression models estimated the association between each experience and acceptance of a hypothetical COVID-19 vaccine. We also explored perceived susceptibility as a potential mediator. Results Intent to vaccinate was lowest in the US and Taiwan, and highest in India, Indonesia, and China. Personal diagnosis with COVID-19 had the greatest impact on intentions to vaccinate across country sites compared to those who experienced a friend or family member diagnosed with COVID-19 or exposures to personal stories reported through media. In India participants that reported a personal diagnosis with COVID-19 had 12.95 times the odds (95% CI: 4.89, 34.28) of accepting a COVID-19 vaccine compared to those with no diagnosis. Higher risk perceptions were associated with higher intention to vaccinate against COVID-19. Conclusions Proximity and seriousness of experiences are influential factors for intention to vaccinate against COVID-19. This study highlights the numerous ways in which pandemic experiences may influence intention to vaccinate against COVID-19 across geographies and cultures, where the course of the pandemic differed.

The reactogenicity and immunogenicity of a booster dose after the second dose of a protein subunit vaccine MVC-COV1901. (preprint)

Abstract: In this extension of the phase 1 clinical study, we report the immunogenicity and reactogenicity of the booster dose of a COVID-19 vaccine, MVC-COV1901, administered six months after the completion of the primary two dose schedule. Antibody persistence was detected at 6 months after the second dose of MVC-COV1901, albeit at reduced levels. At 28 days after the booster dose, the neutralizing antibody titer was 1.7-fold higher compared to the previous peak at 2 weeks after the second dose. These data demonstrated the safety and immunogenicity of booster shot of MVC-COV1901 after the primary schedule of the vaccine.

Changes in COVID-19 risk perceptions: methods of an internet survey conducted in six countries.

OBJECTIVES: This study assessed changes in behaviors/attitudes related to the COVID-19. With the understanding that behaviors and vaccine decision-making could contribute to global spread of infectious diseases, this study collected several waves of internet-based surveys from individuals in the United States, mainland China, Taiwan, Malaysia, Indonesia, and India. The aims of this study were to (1) characterize the relationship between the epidemiology of disease and changes over time in risk perceptions, knowledge, and attitudes towards hygienic behaviors; (2) examine if risk perceptions affect acceptance of less-than-ideal vaccines; and (3) contrast adherence to public health recommendations across countries which have had different governmental responses to the outbreak. DATA DESCRIPTION: We conducted cross-sectional online surveys in six countries from March 2020 to April 2021. By the end of June 2021, there will be six waves of surveys for the United States and China, and four waves for the rest of countries. There are common sets of questions for all countries, however, some questions were adapted to reflect local situations and some questions were designed intentionally for specific countries to capture different COVID-19 mitigation actions. Participants were asked about their adherence towards countermeasures, risk perceptions, and acceptance of a hypothetical vaccine for COVID-19.

Research capacity of global health institutions in China: a gap analysis focusing on their collaboration with other low-income and middle-income countries.

INTRODUCTION: This paper presented qualitative and quantitative data collected on the research capacity of global health institutions in China and aimed to provide a landscaping review of the development of global health as a new discipline in the largest emerging economy of the world. METHODS: Mixed methods were used and they included a bibliometric analysis, a standardised survey and indepth interviews with top officials of 11 selected global health research and educational institutions in mainland China. RESULTS: The bibliometric analysis revealed that each institution had its own focus areas, some with a balanced focus among chronic illness, infectious disease and health systems, while others only focused on one of these areas. Interviews of key staff from each institution showed common themes: recognition that the current research capacity in global health is relatively weak, optimism towards the future, as well as an emphasis on mutual beneficial networking with other countries. Specific obstacles raised and the solutions applied by each institution were listed and discussed. CONCLUSION: Global health institutions in China are going through a transition from learning and following established protocols to taking a more leading role in setting up China's own footprint in this area. Gaps still remain, both in comparison with international institutions, as well as between the leading Chinese institutions and those that have just started. More investment needs to be made, from both public and private domains, to improve the overall capacity as well as the mutual learning and communication within the academic community in China.

Interferon-alpha or -beta facilitates SARS-CoV-2 pulmonary vascular infection by inducing ACE2.

Severe viral pneumonia caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is characterized by a hyperinflammatory state typified by elevated circulating pro-inflammatory cytokines, frequently leading to potentially lethal vascular complications including thromboembolism, disseminated intracellular coagulopathy and vasculitis. Though endothelial infection and subsequent endothelial damage have been described in patients with fatal COVID-19, the mechanism by which this occurs remains elusive, particularly given that, under naïve conditions, pulmonary endothelial cells demonstrate minimal cell surface expression of the SARS-CoV-2 binding receptor ACE2. Herein we describe SARS-CoV-2 infection of the pulmonary endothelium in postmortem lung samples from individuals who died of COVID-19, demonstrating both heterogeneous ACE2 expression and endothelial damage. In primary endothelial cell cultures, we show that SARS-CoV-2 infection is dependent on the induction of ACE2 protein expression and that this process is facilitated by type 1 interferon-alpha (IFNα) or -beta(ß)-two of the main anti-viral cytokines induced in severe SARS-CoV-2 infection-but not significantly by other cytokines (including interleukin 6 and interferon γ/λ). Our findings suggest that the stereotypical anti-viral interferon response may paradoxically facilitate the propagation of COVID-19 from the respiratory epithelium to the vasculature, raising concerns regarding the use of exogenous IFNα/ß in the treatment of patients with COVID-19.

Differential Effect of Vaccine Effectiveness and Safety on COVID-19 Vaccine Acceptance across Socioeconomic Groups in an International Sample.

Controlling the spread of SARS-CoV-2 will require high vaccination coverage, but acceptance of the vaccine could be impacted by perceptions of vaccine safety and effectiveness. The aim of this study was to characterize how vaccine safety and effectiveness impact acceptance of a vaccine, and whether this impact varied over time or across socioeconomic and demographic groups. Repeated cross-sectional surveys of an opt-in internet sample were conducted in 2020 in the US, mainland China, Taiwan, Malaysia, Indonesia, and India. Individuals were randomized into receiving information about a hypothetical COVID-19 vaccine with different safety and effectiveness profiles (risk of fever 5% vs. 20% and vaccine effectiveness 50% vs. 95%). We examined the effect of the vaccine profile on vaccine acceptance in a logistic regression model, and included interaction terms between vaccine profile and socioeconomic/demographic variables to examine the differences in sensitivity to the vaccine profile. In total, 12,915 participants were enrolled in the six-country study, including the US (4054), China (2797), Taiwan (1278), Malaysia (1497), Indonesia (1527), and India (1762). Across time and countries, respondents had stronger preferences for a safer and more effective vaccine. For example, in the US in November 2020, acceptance was 3.10 times higher for a 95% effective vaccine with a 5% risk of fever, vs a vaccine 50% effective, with a 20% risk of fever (95% CI: 2.07, 4.63). Across all countries, there was an increase in the effect of the vaccine profile over time (p < 0.0001), with stronger preferences for a more effective and safer vaccine in November 2020 compared to August 2020. Sensitivity to the vaccine profile was also stronger in August compared to November 2020, in younger age groups, among those with lower income; and in those that are vaccine hesitant. Uptake of COVID-19 vaccines could vary in a country based upon effectiveness and availability. Effective communication tools will need to be developed for certain sensitive groups, including young adults, those with lower income, and those more vaccine hesitant.

A hospital-related outbreak of SARS-CoV-2 associated with variant Epsilon (B.1.429) in Taiwan: transmission potential and outbreak containment under intensified contact tracing, January-February 2021.

OBJECTIVES: A hospital-related cluster of 22 cases of coronavirus disease 2019 (COVID-19) occurred in Taiwan in January-February 2021. Rigorous control measures were introduced and could only be relaxed once the outbreak was declared over. Each day after the apparent outbreak end, we estimated the risk of future cases occurring in order to inform decision-making. METHODS: Probabilistic transmission networks were reconstructed, and transmission parameters (the reproduction number R and overdispersion parameter k) were estimated. The reporting delay during the outbreak was estimated (Scenario 1). In addition, a counterfactual scenario with less effective interventions characterized by a longer reporting delay was considered (Scenario 2). Each day, the risk of future cases was estimated under both scenarios. RESULTS: The values of R and k were estimated to be 1.30 ((95% credible interval (CI) 0.57-3.80) and 0.38 (95% CI 0.12-1.20), respectively. The mean reporting delays considered were 2.5 days (Scenario 1) and 7.8 days (Scenario 2). Following the final case, ttthe inferred probability of future cases occurring declined more quickly in Scenario 1 than Scenario 2. CONCLUSIONS: Rigorous control measures allowed the outbreak to be declared over quickly following outbreak containment. This highlights the need for effective interventions, not only to reduce cases during outbreaks but also to allow outbreaks to be declared over with confidence.