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Front Public Health ; 9: 779720, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34805084

RESUMO

Introduction: With the approval of COVID-19 vaccinations for children and adolescents in China, parental vaccine hesitancy will emerge as a new challenge with regard to the administration of these vaccines. However, little is known regarding this hesitancy as well as regional differences that may exist between parents from Shandong vs. Zhejiang. Methods: To assess these issues, an online survey was conducted via a Wenjuanxing platform over the period from July 22 to August 14, 2021. Parents from Shandong and Zhejiang were recruited from Wechat groups and results from a total of 917 subjects were analyzed. Factors evaluated in this survey included socio-demographic variables, parental vaccine hesitancy, Parental Attitudes toward Childhood Vaccines (PACV) domains (behavior, safety and efficacy, general attitudes) and social support. Results: Compared with those from Shandong (N = 443), parents from Zhejiang (N = 474) showed significantly higher prevalence rates of COVID-19 vaccine hesitancy (19.4 vs. 11.7%, p = 0.001). Multivariate logistic regression showed that yearly household incomes of ≥120,000 RMB (p = 0.041), medical workers (p = 0.022) and general attitudes of PACV (p = 0.004) were risk factors for vaccine hesitancy among parents from Shandong, while behavior (p = 0.004), safety and efficacy (p < 0.001) and general attitudes of PACV (p = 0.002) were risk factors for parents from Zhejiang. Among parents with vaccine hesitancy (N = 144), concerns over side effects (91.0%) and unknown effects (84.0%) of the COVID-19 vaccine were the most prevalent reasons for hesitancy. Evidence providing proof of vaccine safety (67.4%) and assurance of a low risk of being infected by COVID-19 (60.4%) were the two most effective persuasive factors. Conclusion: Parents from Zhejiang showed a higher prevalence of COVID-19 vaccine hesitancy as compared with those from Shandong. Behavior, safety and efficacy, and general attitudes of PACV were the risk factors associated with this hesitancy in these parents from Zhejiang. Given the identification of the various reasons for parental vaccine hesitancy, different strategies as well as regional adjustments in these strategies will be required for an effective and convincing protocol for childhood vaccinations.


Assuntos
COVID-19 , Vacinas , Adolescente , Vacinas contra COVID-19 , Criança , Estudos Transversais , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Pais , Aceitação pelo Paciente de Cuidados de Saúde , SARS-CoV-2 , Vacinação , Vacinas/efeitos adversos
3.
Zhonghua Liu Xing Bing Xue Za Zhi ; 42(7): 1286-1291, 2021 Jul 10.
Artigo em Chinês | MEDLINE | ID: mdl-34814545

RESUMO

To summarize the development and application of tree-based scan statistic (TreeScan), explain the methodology and provide a reference for future use of this method by reviewing the original pharmacoepidemiological and vaccine studies using the TreeScan. Medline, Embase and Web of Science databases were used for the retrieval of eligible studies using keywords related to TreeScan. A total of 15 eligible studies were included, in which 9 studies explored the adverse events of drugs and 6 studies focused on the safety of vaccines. Three types of models (Poisson probability model, Bernoulli probability model and tree-temporal scan statistic model) of TreeScan were used. The major differences among the three models were 1) whether predefined control was used according to research question, 2) whether the time from exposure to onset of adverse events was considered. Several studies explored its ability by comparing with other methods for adverse event detection or by using known adverse events. This review shows that TreeScan is an effective method for the safety signal detection of drugs or vaccines, which develops rapidly and globally. It is very necessary to promote its use in drug safety monitoring and other related fields in China.


Assuntos
Preparações Farmacêuticas , Vacinas , Mineração de Dados , Bases de Dados Factuais , Humanos , Farmacoepidemiologia , Vacinas/efeitos adversos
4.
Vaccine ; 39(48): 6975-6979, 2021 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-34742595

RESUMO

mRNA-based COVID-19 vaccines are effective; however, persistent vaccine hesitancy is partly due to a misperception of their potential adverse events. Non-specific sensory symptoms (NSSS) following immunization are thought to be mediated by stress-related responses. In this case-control study, we evaluated NSSS from a cohort of 7,812,845 BNT162b2 first-dose recipients, of whom 10,929 reported an adverse event following immunization (AEFI). We found an overall frequency of 3.4% (377 cases) or 4.8 cases per 100,000 doses administered. Anatomically, the arms (61%) and face/neck region (36.2%) were the most commonly affected sites. The control group had significantly higher rates of reactogenicity-associated symptoms, suggesting that NSSS are reactogenicity-independent; in multivariable analysis, healthcare workers reported sensory symptoms less frequently (aOR 0.54; 95% CI 0.40-0.72;p < 0.001). This is the first study describing the topography and associated factors for developing NSSS among BNT162b2 recipients. The benign nature of these symptoms may help dissipate hesitation towards this vaccine.


Assuntos
COVID-19 , Vacinas , Vacinas contra COVID-19 , Estudos de Casos e Controles , Humanos , RNA Mensageiro , SARS-CoV-2 , Vacinas/efeitos adversos
6.
Int J Tuberc Lung Dis ; 25(9): 701-707, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34802491

RESUMO

COVID-19 vaccines are considered promising agents in the control of the pandemic. Although their safety was assessed in randomised clinical trials, severe adverse events (AEs) have been reported after large-scale administration. This study aims to evaluate thromboembolic AEs reported after vaccination in a real-world context and how they led to the interruption of vaccination campaigns. We also review the benefits and risks of the vaccines approved in the European Union and provide recommendations. A review of the literature was performed using Medline/PubMed electronic database as well as institutional and pharmacovigilance official reports. Our findings show that vaccine-induced prothrombotic immune thrombocytopenia has been suggested as a very rare AE associated with viral vector vaccines. Unusual thrombotic events combined with moderate-to-severe thrombocytopenia were reported mainly in women under 60 years of age. As safety signals emerged, Vaxzevria and Janssen´s COVID-19 vaccine campaigns have been paused while investigations proceed. On the other hand, the number of deep vein thrombosis and pulmonary embolism reports have not increased. Post-marketing surveillance indicated that mRNA vaccines are safe and should continue to be used. The thrombotic events report rate is not increased in people over 60 years. As they are at greater risk for COVID-19 complications and death, no vaccine restrictions are recommended in this group. Risk factors for vaccine-induced prothrombotic immune thrombocytopenia should be established so that evidence-based decisions can be made. Systematic monitoring of COVID-19 vaccine safety is essential to ensure that the benefits of vaccination outweigh the risks.


Assuntos
COVID-19 , Vacinas , Vacinas contra COVID-19 , Feminino , Humanos , SARS-CoV-2 , Vacinação , Vacinas/efeitos adversos
7.
Rev Saude Publica ; 55: 70, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34730750

RESUMO

The coronavirus disease 2019 (COVID-19) pandemic is significantly causing unprecedented clinical, socioeconomic, and public health challenges globally. The successful global administration of effective, safe and sustainable vaccine(s) is widely believed to be crucial in mitigating as well as preventing COVID-19. However, the rising cases of severe adverse events following immunization (AEFI) with COVID-19 vaccines including thrombosis, thrombocytopenia, and in some instances, death have created serious global concerns and could enormously contribute to vaccine hesitancy. Although the complete underlying pathophysiology and immunopathology of the COVID-19 vaccines related to AEFI, including thrombosis and/or anaphylaxis, are yet to be determined, exploring possible immuno-hypersensitivity could be crucial in the mechanisms associated with these reactions, thereby mitigating their occurrences as well as restoring confidence in vaccine administration for a COVID-19 free world.


Assuntos
COVID-19 , Trombocitopenia , Trombose , Vacinas , Brasil , Vacinas contra COVID-19 , Humanos , SARS-CoV-2 , Vacinas/efeitos adversos
8.
Health Syst Reform ; 7(1): e1991550, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-34780314

RESUMO

The COVID-19 pandemic poses an extraordinary threat to the health, safety, and freedom of temporary foreign workers (TFWs). Highly effective vaccines against COVID-19 may hold an outsized benefit for TFWs, particularly those living in congregate settings where protective measures such as social distancing are not possible. While some studies of migrant destination countries have included migrants, no study to date has sought to understand variations in vaccine hesitancy among individuals in a single migrant source population across different destinations. Such a design is critical for understanding how the context of immigration affects levels of hesitancy among migrants from similar conditions of origin. This observational study leverages longitudinal data from an ongoing monthly rapid-response survey of TFWs from Bangladesh (n = 360). Overall vaccine hesitancy was 25%, with significant variation by host country. Multivariate analyses confirmed that immigration system factors and threat perception are the strongest predictors of COVID-19 vaccine hesitancy for TFWs. The predicted probability of hesitancy for an undocumented TFW was 0.405, while the predicted probability for those with valid visas was 0.207 (p < .01). The probability of being hesitant for TFWs who were worried about getting COVID-19 was 0.129 compared to 0.305 (p < .01) for those who were not worried. Results reveal low vaccine hesitancy among TFWs from Bangladesh with differences in location, undocumented status, COVID-19 threat perception, and level of worry about side effects. There could be relatively high returns for targeting vaccine access and distribution to TFWs because of their high levels of vaccine acceptance.


Assuntos
COVID-19 , Vacinas , Bangladesh , Vacinas contra COVID-19 , Humanos , Pandemias , SARS-CoV-2 , Vacinação , Vacinas/efeitos adversos
9.
Ageing Res Rev ; 72: 101486, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34673261

RESUMO

We read with great interest the article "Underrepresentation of older adults in clinical trials on COVID-19 vaccines: A systematic review" written by Nicola Veronese et al. This important work demonstrated that medications and vaccines commonly used in older adults have not been adequately evaluated. Concerning this systematic review, we shall like to mention some certain points deserved to be attended by the authors.


Assuntos
COVID-19 , Vacinas , Idoso , Vacinas contra COVID-19 , Humanos , SARS-CoV-2 , Vacinas/efeitos adversos
12.
Mo Med ; 118(5): 404-407, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34658424
13.
J Allergy Clin Immunol Pract ; 9(10): 3584-3597, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34627533

RESUMO

The development and widespread use of vaccination over the past centuries has been the single most impactful intervention in public health, by effectively preventing morbidity and mortality from infectious diseases. Vaccination is generally well tolerated in the vast majority of the population, and the benefits of vaccination largely outweigh the risk of severe adverse events in the majority of patients. Vaccine hesitancy can be a significant concern and lead to infectious disease outbreaks. All health care providers play an important role in maintaining public confidence in vaccines because their attitude and knowledge is often critical in facilitating acceptance of a vaccine. The purpose of this review is to first, provide an understanding of the basic concepts that are relevant to vaccine pharmacovigilance, and secondly, to provide an overview and discuss management of both immune and nonimmune adverse events after vaccination.


Assuntos
Vacinas , Surtos de Doenças , Pessoal de Saúde , Humanos , Saúde Pública , Vacinação , Vacinas/efeitos adversos
14.
Vaccine ; 39(44): 6464-6469, 2021 10 22.
Artigo em Inglês | MEDLINE | ID: mdl-34598820

RESUMO

Among 6146 hospital employees, 118 subjects with severe allergic background were identified through a screening questionnaire and stratified into 3 groups (Low-risk (LR), Intermediate (IR) and High-risk (HR) group), based on their allergic anamnesis. Data reports on hypersensitivity reactions (HypR) have been collected in both allergic and non-allergic subjects. Seventeen patients (14%) in the allergic population had a HypR after the first, the second or both doses. Skin manifestations were the most frequent ones. Allergic events were more frequent in HR (35%) than IR (10%; p = 0.005) or LR (0%; p = 0.074) subjects. No patient had anaphylaxis. All patients completed the vaccination schedule. 13 HypR occurred in patients without severe allergic background (13/6028, 0,2%) including one (1/6148, 0.016% of total population) WAO grade-4 anaphylaxis. Our data suggest that BNT162b2 mRNA Covid-19 vaccine is relatively safe also in patients with severe allergic background; however, some precautions are required for high-risk patients.


Assuntos
Anafilaxia , COVID-19 , Vacinas , Algoritmos , Anafilaxia/induzido quimicamente , Anafilaxia/diagnóstico , Anafilaxia/epidemiologia , Vacinas contra COVID-19 , Humanos , SARS-CoV-2 , Vacinas/efeitos adversos
15.
Clin Imaging ; 80: 348-352, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34507266

RESUMO

Although vaccination against Coronavirus disease-2019 (COVID-19) is still occurring, several adverse effects temporally related to these vaccines are already being reported, even if through isolated case reports. In the present study, we describe the lesions seen on magnetic resonance imaging (MRI) of three patients who developed neurological symptoms after receiving the ChAdOX1 nCoV-19 vaccine (Oxford/AstraZeneca). The first patient presented with an ischemic stroke in the posterior limb of the left internal capsule, two days after vaccination. The second patient presented with a left facial nerve palsy, seven days after vaccination. The third patient presented with myelitis, eight days after receiving the vaccine. All patients presented the symptoms after the first dose of the vaccine and did not have a history of previous COVID-19. The real incidence of these types of complications is not known yet, but it is important to consider the possibility of COVID-19 vaccine complications, in patients with a recent history of vaccination and recent development of neurological symptoms, even though this association is only casual. Longitudinal studies are necessary to further analyze the incidence of the adverse effects of each vaccine against SARS-CoV-2.


Assuntos
COVID-19 , Vacinas , Vacinas contra COVID-19 , Humanos , Neuroimagem , SARS-CoV-2 , Vacinas/efeitos adversos
16.
BMJ Glob Health ; 6(9)2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34475024

RESUMO

BACKGROUND: Several studies have highlighted that vaccine hesitancy (VH) is among the most important threats to global health, especially in low- and middle-income countries, including the Philippines. However, there is a dearth of literature exploring family experiences of-or concerns related to-childhood vaccinations that gives voice to vaccine hesitant caregivers (VHCs) of small children. Here, we present insights from VHCs from the Philippines. METHODS: This research draws on in-depth interviews (IDIs) with 44 VHCs who had previously delayed or refused vaccination for their children in rural and urban communities in Cavite Province, the Philippines. Amid the COVID-19 pandemic, we conducted IDIs via an online platform of the respondents' choosing (ie, Facebook messenger call, Skype and Zoom). All interviews were recorded, transcribed, translated and analysed drawing from the tenets of constructivist grounded theory. We use the social ecological model to structure our results. RESULTS: Among the reasons for delay or refusal of childhood vaccinations, a fear of side effects emerged as the most salient concern, exacerbated by previous negative experiences (including trauma) from a dengue vaccine controversy in 2017. Respondents cited the dengue vaccine controversy as they expressed reluctance (regarding any new vaccines) and suspicion (towards school-based vaccination, the distribution channel used for the dengue vaccine). Heads of households opposing vaccines, perceptions that vaccines are non-essential and influences from the social and traditional media or neighbours contributed to further refusal and delay. Upon probing, VHCs recounted health system concerns particularly with regards to healthcare workers who are sometimes unable to answer their questions and can be dismissive or disrespectful regarding caregivers' concerns. CONCLUSION: Understanding VH from the lens of VHCs highlights pathways for interventions to regain trust and bolster confidence towards vaccines. Our findings may serve as linchpins in the development of VH interventions aiming at changing behaviour on a population scale.


Assuntos
COVID-19 , Vacinas , Cuidadores , Medo , Humanos , Pandemias , Filipinas , SARS-CoV-2 , Vacinas/efeitos adversos
17.
BMC Public Health ; 21(1): 1686, 2021 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-34530804

RESUMO

BACKGROUND: Vaccine hesitancy has been a growing challenge for public health in recent decades. Among factors contributing to vaccine hesitancy, concerns regarding vaccine safety and Adverse Events (AEs) play the leading role. Moreover, cognitive biases are critical in connecting such concerns to vaccine hesitancy behaviors, but their role has not been comprehensively studied. In this study, our first objective is to address concerns regarding vaccine AEs to increase vaccine acceptance. Our second objective is to identify the potential cognitive biases connecting vaccine hesitancy concerns to vaccine-hesitant behaviors and identify the mechanism they get triggered in the vaccine decision-making process. METHODS: First, to mitigate concerns regarding AEs, we quantitatively analyzed the U.S. Vaccine Adverse Event Reporting System (VAERS) from 2011 to 2018 and provided evidence regarding the non-severity of the AEs that can be used as a communicable summary to increase vaccine acceptance. Second, we focused on the vaccination decision-making process. We reviewed cognitive biases and vaccine hesitancy literature to identify the most potential cognitive biases that affect vaccine hesitancy and categorized them adopting the Precaution Adoption Process Model (PAPM). RESULTS: Our results show that the top frequent AEs are expected mild reactions like injection site erythema (4.29%), pyrexia (3.66%), and injection site swelling (3.21%). 94.5% of the reports are not serious and the average population-based serious reporting rate over the 8 years was 25.3 reports per 1 million population. We also identified 15 potential cognitive biases that might affect people's vaccination decision-making and nudge them toward vaccine hesitancy. We categorized these biases based on the factors that trigger them and discussed how they contribute to vaccine hesitancy. CONCLUSIONS: This paper provided an evidence-based communicable summary of VAERS. As the most trusted sources of vaccine information, health practitioners can use this summary to provide evidence-based vaccine information to vaccine decision-makers (patients/parents) and mitigate concerns over vaccine safety and AEs. In addition, we identified 15 potential cognitive biases that might affect the vaccination decision-making process and nudge people toward vaccine hesitancy. Any plan, intervention, and message to increase vaccination uptake should be modified to decrease the effect of these potential cognitive biases.


Assuntos
Sistemas de Notificação de Reações Adversas a Medicamentos , Vacinas , Viés , Cognição , Humanos , Vacinação/efeitos adversos , Vacinas/efeitos adversos
18.
Schweiz Arch Tierheilkd ; 163(9): 545-552, 2021 Sep.
Artigo em Alemão | MEDLINE | ID: mdl-34465558

RESUMO

INTRODUCTION: The aim of the vigilance system in Switzerland is the evaluation and classification of reported suspected adverse reactions of immunological veterinary medicines (IVMP), including suspected lack of expected efficacy. The Institute of Virology and Immunology (IVI) is the competent authority for marketing authorizations of immunological veterinary medicinal products in Switzerland and responsible for the vaccinovigilance system. In 2020, 130 adverse reaction reports were received (5% less compared to 2019). The reports mainly concerned dogs (41%) and cats (25%) followed by cattle (18%) and horses (7%). Many of the reports in dogs involved the application of combined vaccines against canine distemper, hepatitis, parvovirosis and parainfluenza in combination with canine leptospira components, in cats against cat flu and feline panleukopenia in combination with feline leukaemia virus infection. Causality assessments were done according to the international ABON system. In 27% of the reported cases, the causality assessments between the vaccination and the reaction described were evaluated as being probable (ABON A), in 44% as possible (ABON B).


Assuntos
Vacinas , Drogas Veterinárias , Vacinas Virais , Animais , Bovinos , Cães , Cavalos , Suíça , Vacinação/efeitos adversos , Vacinação/veterinária , Vacinas/efeitos adversos , Vacinas Combinadas , Drogas Veterinárias/efeitos adversos , Vacinas Virais/efeitos adversos
19.
Front Immunol ; 12: 690328, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34557188

RESUMO

Vaccination is the most effective measure to prevent infections in the general population. Its efficiency strongly depends on the function and composition of the immune system. If the immune system lacks critical components, patients will not be fully protected despite a completed vaccination schedule. Antigen-specific serum immunoglobulin levels are broadly used correlates of protection. These are the products of terminally differentiated B cells - plasma cells. Here we reviewed the literature on how aberrancies in B-cell composition and function influence immune responses to vaccinations. In a search through five major literature databases, 6,537 unique articles published from 2000 and onwards were identified. 75 articles were included along three major research lines: extremities of life, immunodeficiency and immunosuppression. Details of the protocol can be found in the International Prospective Register of Systematic Reviews [PROSPERO (registration number CRD42021226683)]. The majority of articles investigated immune responses in adults, in which vaccinations against pneumococci and influenza were strongly represented. Lack of baseline information was the most common reason of exclusion. Irrespective of study group, three parameters measured at baseline seemed to have a predictive value in assessing vaccine efficacy: (1) distribution of B-cell subsets (mostly a reduction in memory B cells), (2) presence of exhausted/activated B cells, or B cells with an aberrant phenotype, and (3) pre-existing immunological memory. In this review we showed how pre-immunization (baseline) knowledge of circulating B cells can be used to predict vaccination efficacy. We hope that this overview will contribute to optimizing vaccination strategies, especially in immunocompromised patients.


Assuntos
Linfócitos B/imunologia , Hospedeiro Imunocomprometido , Imunogenicidade da Vacina , Imunofenotipagem , Vacinação , Vacinas/administração & dosagem , Linfócitos B/metabolismo , Biomarcadores/metabolismo , Humanos , Segurança do Paciente , Fenótipo , Valor Preditivo dos Testes , Medição de Risco , Fatores de Risco , Resultado do Tratamento , Vacinação/efeitos adversos , Vacinas/efeitos adversos
20.
Trials ; 22(1): 592, 2021 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-34488843

RESUMO

OBJECTIVES: Vaccine hesitancy is a major hurdle for stopping the COVID-19 pandemic. Recently, fear of vaccine side effects created widespread concern and paused global vaccination efforts. Many studies find that how medical risks are framed and communicated can influence individuals' perceptions and behavior, yet there is little evidence on how the communication of COVID-19 vaccine side-effect risks influences vaccine intentions. The primary objective of our study is to evaluate how the framing of vaccine-side effect risks impacts individuals' vaccine intentions and perceptions of vaccine safety. The study will assess the impact of 3 dimensions of side-effect framing: 1. Qualitative risk labels: Determine whether attaching a qualitative risk label (e.g. adding "very low risk" next to the actual numerical risk) impacts individuals' willingness to take a vaccine and their perceptions of its safety. 2. Comparison groups: Determine how framing side-effect risks in comparison to other causes of mortality (COVID-19 mortality and motor vehicle mortality) impacts individuals' willingness to take a vaccine and their perceptions of its safety. 3. How the comparison risks are presented: Determine whether comparisons to other causes of mortality are presented on an absolute or relative scale impacts individuals' willingness to take a vaccine and their perceptions of its safety. Secondarily, we will also randomize a subset of individuals to receive the "status-quo" framing, where the vaccine side-effect risks are presented like how they were presented in the media. We will then compare vaccine intentions and perceptions of vaccine safety between the status-quo and the pooled intervention group samples to provide some insight into how "harmful" the status-quo framing was. Ultimately, we believe that our results will provide the some of the first experimental evidence on how the communication of COVID-19 vaccine risks may impact the public's willingness to be vaccinated and can inform future efforts to increase vaccination rates. TRIAL DESIGN: Our study is an online-based randomized controlled trial designed to evaluate the effect of different vaccine side-effect framings on COVID-19 vaccine intentions and perceived safety for a hypothetical COVID-19 vaccine. Using a factorial design, we will experimentally assess the impact of 3 risk framing strategies, varying whether the risk is presented: (1) with a qualitative label, (2) whether the risk is presented with a comparison risk, and (3) for comparison cases, whether the comparison is in absolute or relative terms. We will also randomize a portion of respondents to a status quo framing where the side effect risk mimics the media's communication in early April 2021. PARTICIPANTS: This will be an online study setting. We will use Prolific to recruit participants and host our study on the Gorilla platform. To be eligible, participants must be 18 years old or over (male, female, or other), have current residence in the US or UK, and be able to speak English. Participants will be excluded from the study if they do not meet our inclusion criteria. INTERVENTION AND COMPARATOR: Our study content will consist of five pages presented to individuals online. Page 1 will explain the purpose of the study and contain the consent information. Page 2 will contain basic sociodemographic questions, including participants' age, sex, and schooling level. Page 3 will set up the experiment by telling individuals that we will describe a hypothetical new COVID-19 vaccine and that we would like to know how likely they would be to take the vaccine and how safe they think the vaccine is. On this page, we will also encourage individuals to respond truthfully and remind them that their answers are confidential and cannot be linked back to any personal identifying information. Page 4 will be the main experimental slide, where we will present individuals with information on the vaccine, varying how the vaccination risk is communicated based on which experimental framing arm they are randomized to. We will factorially randomize across the following factors in the following order (separately by country). First, we will determine whether individuals are randomized to the status quo framing, or the intervention framings (1500 respondents to the status quo, and 4500 to the intervention). Among those randomized to the intervention framing, we will randomize (equal allocation) whether the side effect is presented without a comparison, with a comparison to COVID-19 mortality, or with a comparison to motor vehicle mortality. We will then factorially randomize (equal allocation) whether the risk is presented with a qualitative risk label or not (e.g. "very low risk"). To ensure that the factors are independent of one another, we will do this by randomizing individuals to the risk labels within strata of the comparison group factor. Lastly, among those randomized to the comparison group, we will factorially randomize whether the risk is presented as an absolute or relative comparison. As previously, we will ensure independence by doing this randomization within strata of comparison group*risk labelling. This entire design is visualized in the full protocol. The experimental text for each arm is: Arm 1: With regards to side effects, so far 8 individuals have developed potentially life-threatening blood clots. This is among the approximately 7 million adults that have received the vaccine so far. Arm 2: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots. Arm 3: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots (very low risk). Arm 4: Text for USA participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots. As a reference, 170 out of every 100,000 unvaccinated Americans died of COVID-19 based on data from the past year. Text for UK participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots. As a reference, 108 out of every 100,000 unvaccinated individuals in the UK died of COVID-19 based on data from the past year. Arm 5: Text for USA participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots. As a reference, this is 1/170th of the risk of COVID-19 mortality among unvaccinated Americans based on data from the past year. Text for UK participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots. As a reference, this is 1/108th of the risk of COVID-19 mortality among unvaccinated individuals in the UK based on data from the past year. Arm 6: Text for USA participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots (very low risk). As a reference, 170 out of every 100,000 unvaccinated Americans died of COVID-19 based on data from the past year. Text for UK participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots (very low risk). As a reference, 108 out of every 100,000 unvaccinated individuals in the UK died of COVID-19 based on data from the past year. Arm 7: Text for USA participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots (very low risk). As a reference, this is 1/170th of the risk of COVID-19 mortality among unvaccinated Americans based on data from the past year. Text for UK participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots (very low risk). As a reference, this is 1/108th of the risk of COVID-19 mortality among unvaccinated individuals in the UK based on data from the past year. Arm 8: Text for USA participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots. As a reference, 12 out of every 100,000 Americans died in a motor vehicle accident based on data from the past year. Text for UK participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots. As a reference, 2.6 out of every 100,000 individuals in the UK died in a motor vehicle accident based on data from the past year. Arm 9: Text for USA participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots. As a reference, this is 1/12th of the risk of dying in a motor vehicle accident based on data from the past year. Text for UK participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots. As a reference, this is almost 1/4th of the risk of dying in a motor vehicle accident based on data from the past year. Arm 10: Text for USA participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots (very low risk). As a reference, 12 out of every 100,000 Americans died in a motor vehicle accident based on data from the past year. Text for UK participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots (very low risk). As a reference, 2.6 out of every 100,000 individuals in the UK died in a motor vehicle accident based on data from the past year. Arm 11: Text for USA participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots (very low risk). As a reference, this is 1/12th of the risk of dying in a motor vehicle accident based on data from the past year. Text for UK participants: With regards to side effects, 1 out of 100,000 vaccinated individuals may develop serious blood clots (very low risk). As a reference, this is nearly 1/4th of the risk of dying in a motor vehicle accidentbased on data from the past year. The risk information will be presented on a single page along with the two main outcome questions. Lastly, for individuals that reported that they are unlikely or unsure about whether they would take the vaccine, the final page will ask them their reason (question based on a recently published study of COVID-19 vaccine hesitancy). MAIN OUTCOMES: Our primary outcome is individuals' willingness to take the hypothetical COVID-19 vaccine. We will measure this outcome by asking, "How likely would you be to take this vaccine?" allowing individuals to choose from a four-point Likert response of "Unlikely, Unsure leaning towards unlikely, Unsure leaning towards likely, Very likely." This outcome variable, including the categories and phrasing, is based on a recently published study on COVID-19 vaccine hesitancy conducted by researchers with the Vaccine Hesitance Project at the London School of Hygiene and Tropical Medicine. Our secondary outcome is individuals' perceived safety of the vaccine. We will assess this outcome by asking individuals, "How safe do you feel this vaccine is?" allowing them to choose answers ranging from 1-10 where 1 is extremely unsafe, and 10 is extremely safe. Both outcomes will be measured at the time of the questionnaire. Participants can take up to 45 min to complete the questions but will not be able to go back and change their responses after submitting their questionnaire. RANDOMIZATION: Using a web-based randomization algorithm, Gorilla will randomly allocate participants to each of the experimental arms. Gorilla allows for two randomization options - independent randomization of each individual based on a probability draw and balanced randomization, which randomizes without replacement such that among groups of respondents a fixed proportion will end up in each experimental arm. We will use the "balanced randomization" option to ensure that our experimental arms are balanced. Participants will be randomized based on the allocations described above. BLINDING: Because Prolific handles the interaction between the study investigators and participants, the participants will be completely anonymous to the study investigators. The outcome measures will be self-reported and submitted anonymously. All persons in the study team will be blinded to the group allocation. NUMBERS TO BE RANDOMIZED: We will randomize 6000 participants per country for a total sample of 12000 individuals. TRIAL STATUS: The protocol version number is 1.0 and the date is July 14, 2021. Recruitment is expected to begin on 26 July 2021 and end by August 10, 2021. TRIAL REGISTRATION: The study and its outcomes were registered at the German Clinical Trials Register ( www.drks.de ) on July 12th, 2021: # DRKS00025551 . FULL PROTOCOL: The full protocol is attached as an additional file, accessible from the Trials website (Full_Protocol_20Jul2021) In the interest of expediting dissemination of this material, the familiar formatting has been eliminated; this Letter serves as a summary of the key elements of the full protocol.


Assuntos
COVID-19 , Vacinas , Adolescente , Adulto , Vacinas contra COVID-19 , Feminino , Humanos , Intenção , Masculino , Pandemias , Ensaios Clínicos Controlados Aleatórios como Assunto , SARS-CoV-2 , Resultado do Tratamento , Reino Unido , Estados Unidos , Vacinas/efeitos adversos
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