Several coronavirus disease 2019 (COVID-19) vaccines are currently in human trials. In June 2020, we surveyed 13,426 people in 19 countries to determine potential acceptance rates and factors influencing acceptance of a COVID-19 vaccine. Of these, 71.5% of participants reported that they would be very or somewhat likely to take a COVID-19 vaccine, and 48.1% reported that they would accept their employer's recommendation to do so. Differences in acceptance rates ranged from almost 90% (in China) to less than 55% (in Russia). Respondents reporting higher levels of trust in information from government sources were more likely to accept a vaccine and take their employer's advice to do so.

/pdf/a-global-survey-of-potential-acceptance-of-a-covid-19-17q43t1ycf.pdf

A global survey of potential acceptance of a COVID-19 vaccine.

COVID-19 Vaccine Hesitancy Worldwide: A Concise Systematic Review of Vaccine Acceptance Rates.

Identifying and understanding COVID-19 vaccine hesitancy within distinct populations may aid future public health messaging. Using nationally representative data from the general adult populations of Ireland (N = 1041) and the United Kingdom (UK; N = 2025), we found that vaccine hesitancy/resistance was evident for 35% and 31% of these populations respectively. Vaccine hesitant/resistant respondents in Ireland and the UK differed on a number of sociodemographic and health-related variables but were similar across a broad array of psychological constructs. In both populations, those resistant to a COVID-19 vaccine were less likely to obtain information about the pandemic from traditional and authoritative sources and had similar levels of mistrust in these sources compared to vaccine accepting respondents. Given the geographical proximity and socio-economic similarity of the populations studied, it is not possible to generalize findings to other populations, however, the methodology employed here may be useful to those wishing to understand COVID-19 vaccine hesitancy elsewhere.

/pdf/psychological-characteristics-associated-with-covid-19-4j1ghzmk6h.pdf

Psychological characteristics associated with COVID-19 vaccine hesitancy and resistance in Ireland and the United Kingdom.

Background Monitoring the reasons why a considerable number of people do not receive recommended vaccinations allows identification of important trends over time, and designing and evaluating strategies to address vaccine hesitancy and increase vaccine uptake. Existing validated measures assessing vaccine hesitancy focus primarily on confidence in vaccines and the system that delivers them. However, empirical and theoretical work has stated that complacency (not perceiving diseases as high risk), constraints (structural and psychological barriers), calculation (engagement in extensive information searching), and aspects pertaining to collective responsibility (willingness to protect others) also play a role in explaining vaccination behavior. The objective was therefore to develop a validated measure of these 5C psychological antecedents of vaccination. Methods and findings Three cross-sectional studies were conducted. Study 1 uses factor analysis to develop an initial scale and assesses the sub-scales' convergent, discriminant, and concurrent validity (N = 1,445, two German convenience-samples). In Study 2, a sample representative regarding age and gender for the German population (N = 1,003) completed the measure for vaccination in general and for specific vaccinations to assess the potential need for a vaccine-specific wording of items. Study 3 compared the novel scale's performance with six existing measures of vaccine hesitancy (N = 350, US convenience-sample). As an outcome, a long (15-item) and short (5-item) 5C scale were developed as reliable and valid indicators of confidence, complacency, constraints, calculation, and collective responsibility. The 5C sub-scales correlated with relevant psychological concepts, such as attitude (confidence), perceived personal health status and invulnerability (complacency), self-control (constraints), preference for deliberation (calculation), and communal orientation (collective responsibility), among others. The new scale provided similar results when formulated in a general vs. vaccine-specific way (Study 2). In a comparison of seven measures the 5C scale was constantly among the scales that explained the highest amounts of variance in analyses predicting single vaccinations (between 20% and 40%; Study 3). The present studies are limited to the concurrent validity of the scales. Conclusions The 5C scale provides a novel tool to monitor psychological antecedents of vaccination and facilitates diagnosis, intervention design and evaluation. Its short version is suitable for field settings and regular global monitoring of relevant antecedents of vaccination.

/pdf/beyond-confidence-development-of-a-measure-assessing-the-5c-3x841cmgxv.pdf

Beyond confidence: Development of a measure assessing the 5C psychological antecedents of vaccination.

Background Understanding the threat posed by anti-vaccination efforts on social media is critically important with the forth coming need for world wide COVID-19 vaccination programs. We globally evaluate the effect of social media and online foreign disinformation campaigns on vaccination rates and attitudes towards vaccine safety. Methods We use a large-n cross-country regression framework to evaluate the effect of social media on vaccine hesitancy globally. To do so, we operationalize social media usage in two dimensions: the use of it by the public to organize action (using Digital Society Project indicators), and the level of negatively oriented discourse about vaccines on social media (using a data set of all geocoded tweets in the world from 2018-2019). In addition, we measure the level of foreign-sourced coordinated disinformation operations on social media ineach country (using Digital Society Project indicators). The outcome of vaccine hesitancy is measured in two ways. First, we use polls of what proportion of the public per country feels vaccines are unsafe (using Wellcome Global Monitor indicators for 137 countries). Second, we use annual data of actual vaccination rates from the WHO for 166 countries. Results We found the use of social media to organise offline action to be highly predictive of the belief that vaccinations are unsafe, with such beliefs mounting as more organisation occurs on social media. In addition, the prevalence of foreign disinformation is highly statistically and substantively significant in predicting a drop in mean vaccination coverage over time. A 1-point shift upwards in the 5-point disinformation scale is associated with a 2-percentage point drop in mean vaccination coverage year over year. We also found support for the connection of foreign disinformation with negative social media activity about vaccination. The substantive effect of foreign disinformation is to increase the number of negative vaccine tweets by 15% for the median country. Conclusion There is a significant relationship between organisation on social media and public doubts of vaccine safety. In addition, there is a substantial relationship between foreign disinformation campaigns and declining vaccination coverage.

https://gh.bmj.com/content/bmjgh/5/10/e004206.full.pdf

Social media and vaccine hesitancy.

Vaccine hesitancy around the globe: Analysis of three years of WHO/UNICEF Joint Reporting Form data-2015-2017.

CONTEXT: Several varicella vaccines are available worldwide. Countries with a varicella vaccination program use 1- or 2-dose schedules. OBJECTIVE: We examined postlicensure estimates of varicella vaccine effectiveness (VE) among healthy children. DATA SOURCES: Systematic review and descriptive and meta-analysis of Medline, Embase, Cochrane libraries, and CINAHL databases for reports published during 1995–2014. STUDY SELECTION: Publications that reported original data on dose-specific varicella VE among immunocompetent children. DATA EXTRACTION: We used random effects meta-analysis models to obtain pooled one dose VE estimates by disease severity (all varicella and moderate/severe varicella). Within each severity category, we assessed pooled VE by vaccine and by study design. We used descriptive statistics to summarize 1-dose VE against severe disease. For 2-dose VE, we calculated pooled estimates against all varicella and by study design. RESULTS: The pooled 1-dose VE was 81% (95% confidence interval [CI]: 78%–84%) against all varicella and 98% (95% CI: 97%–99%) against moderate/severe varicella with no significant association between VE and vaccine type or study design (P > .1). For 1 dose, median VE for prevention of severe disease was 100% (mean = 99.4%). The pooled 2-dose VE against all varicella was 92% (95% CI: 88%–95%), with similar estimates by study design. LIMITATIONS: VE was assessed primarily during outbreak investigations and using clinically diagnosed varicella. CONCLUSIONS: One dose of varicella vaccine was moderately effective in preventing all varicella and highly effective in preventing moderate/severe varicella, with no differences by vaccine. The second dose adds improved protection against all varicella.

Global Varicella Vaccine Effectiveness: A Meta-analysis

Vaccine hesitancy has become the focus of growing attention and concern globally despite overwhelming evidence of the value of vaccines in preventing disease and saving the lives of millions of individuals every year. Measuring vaccine hesitancy and its determinants worldwide is important in order to understand the scope of the problem and for the development of evidence-based targeted strategies to reduce hesitancy. Two indicators to assess vaccine hesitancy were developed to capture its nature and scope at the national and subnational level to collect data in 2014: 1) The top 3 reasons for not accepting vaccines according to the national schedule in the past year and whether the response was opinion- or assessment-based and 2) Whether an assessment (or measurement) of the level of confidence in vaccination had taken place at national or subnational level in the previous 5 years. The most frequently cited reasons for vaccine hesitancy globally related to (1) the risk-benefit of vaccines, (2) knowledge and awareness issues, (3) religious, cultural, gender or socio-economic factors. Major issues were fear of side effects, distrust in vaccination and lack of information on immunization or immunization services. The analysis revealed that 29% of all countries had done an assessment of the level of confidence in their country, suggesting that vaccine confidence was an issue of importance. Monitoring vaccine hesitancy is critical because of its influence on the success of immunization programs. To our knowledge, the proposed indicators provide the first global snapshot of reasons driving vaccine hesitancy and depicting its widespread nature, as well as the extent of assessments conducted by countries.

/pdf/assessments-of-global-drivers-of-vaccine-hesitancy-in-2014-18efxs0hyp.pdf

Assessments of global drivers of vaccine hesitancy in 2014—Looking beyond safety concerns

Response to additional COVID-19 vaccine doses in people who are immunocompromised: a rapid review

Abstract Background Different forms of vaccines have been developed to prevent the SARS‐CoV‐2 virus and subsequent COVID‐19 disease. Several are in widespread use globally. Objectives To assess the efficacy and safety of COVID‐19 vaccines (as a full primary vaccination series or a booster dose) against SARS‐CoV‐2. Search methods We searched the Cochrane COVID‐19 Study Register and the COVID‐19 L·OVE platform (last search date 5 November 2021). We also searched the WHO International Clinical Trials Registry Platform, regulatory agency websites, and Retraction Watch. Selection criteria We included randomized controlled trials (RCTs) comparing COVID‐19 vaccines to placebo, no vaccine, other active vaccines, or other vaccine schedules. Data collection and analysis We used standard Cochrane methods. We used GRADE to assess the certainty of evidence for all except immunogenicity outcomes. We synthesized data for each vaccine separately and presented summary effect estimates with 95% confidence intervals (CIs). Main results We included and analyzed 41 RCTs assessing 12 different vaccines, including homologous and heterologous vaccine schedules and the effect of booster doses. Thirty‐two RCTs were multicentre and five were multinational. The sample sizes of RCTs were 60 to 44,325 participants. Participants were aged: 18 years or older in 36 RCTs; 12 years or older in one RCT; 12 to 17 years in two RCTs; and three to 17 years in two RCTs. Twenty‐nine RCTs provided results for individuals aged over 60 years, and three RCTs included immunocompromized patients. No trials included pregnant women. Sixteen RCTs had two‐month follow‐up or less, 20 RCTs had two to six months, and five RCTs had greater than six to 12 months or less. Eighteen reports were based on preplanned interim analyses. Overall risk of bias was low for all outcomes in eight RCTs, while 33 had concerns for at least one outcome. We identified 343 registered RCTs with results not yet available. This abstract reports results for the critical outcomes of confirmed symptomatic COVID‐19, severe and critical COVID‐19, and serious adverse events only for the 10 WHO‐approved vaccines. For remaining outcomes and vaccines, see main text. The evidence for mortality was generally sparse and of low or very low certainty for all WHO‐approved vaccines, except AD26.COV2.S (Janssen), which probably reduces the risk of all‐cause mortality (risk ratio (RR) 0.25, 95% CI 0.09 to 0.67; 1 RCT, 43,783 participants; high‐certainty evidence). Confirmed symptomatic COVID‐19 High‐certainty evidence found that BNT162b2 (BioNtech/Fosun Pharma/Pfizer), mRNA‐1273 (ModernaTx), ChAdOx1 (Oxford/AstraZeneca), Ad26.COV2.S, BBIBP‐CorV (Sinopharm‐Beijing), and BBV152 (Bharat Biotect) reduce the incidence of symptomatic COVID‐19 compared to placebo (vaccine efficacy (VE): BNT162b2: 97.84%, 95% CI 44.25% to 99.92%; 2 RCTs, 44,077 participants; mRNA‐1273: 93.20%, 95% CI 91.06% to 94.83%; 2 RCTs, 31,632 participants; ChAdOx1: 70.23%, 95% CI 62.10% to 76.62%; 2 RCTs, 43,390 participants; Ad26.COV2.S: 66.90%, 95% CI 59.10% to 73.40%; 1 RCT, 39,058 participants; BBIBP‐CorV: 78.10%, 95% CI 64.80% to 86.30%; 1 RCT, 25,463 participants; BBV152: 77.80%, 95% CI 65.20% to 86.40%; 1 RCT, 16,973 participants). Moderate‐certainty evidence found that NVX‐CoV2373 (Novavax) probably reduces the incidence of symptomatic COVID‐19 compared to placebo (VE 82.91%, 95% CI 50.49% to 94.10%; 3 RCTs, 42,175 participants). There is low‐certainty evidence for CoronaVac (Sinovac) for this outcome (VE 69.81%, 95% CI 12.27% to 89.61%; 2 RCTs, 19,852 participants). Severe or critical COVID‐19 High‐certainty evidence found that BNT162b2, mRNA‐1273, Ad26.COV2.S, and BBV152 result in a large reduction in incidence of severe or critical disease due to COVID‐19 compared to placebo (VE: BNT162b2: 95.70%, 95% CI 73.90% to 99.90%; 1 RCT, 46,077 participants; mRNA‐1273: 98.20%, 95% CI 92.80% to 99.60%; 1 RCT, 28,451 participants; AD26.COV2.S: 76.30%, 95% CI 57.90% to 87.50%; 1 RCT, 39,058 participants; BBV152: 93.40%, 95% CI 57.10% to 99.80%; 1 RCT, 16,976 participants). Moderate‐certainty evidence found that NVX‐CoV2373 probably reduces the incidence of severe or critical COVID‐19 (VE 100.00%, 95% CI 86.99% to 100.00%; 1 RCT, 25,452 participants). Two trials reported high efficacy of CoronaVac for severe or critical disease with wide CIs, but these results could not be pooled. Serious adverse events (SAEs) mRNA‐1273, ChAdOx1 (Oxford‐AstraZeneca)/SII‐ChAdOx1 (Serum Institute of India), Ad26.COV2.S, and BBV152 probably result in little or no difference in SAEs compared to placebo (RR: mRNA‐1273: 0.92, 95% CI 0.78 to 1.08; 2 RCTs, 34,072 participants; ChAdOx1/SII‐ChAdOx1: 0.88, 95% CI 0.72 to 1.07; 7 RCTs, 58,182 participants; Ad26.COV2.S: 0.92, 95% CI 0.69 to 1.22; 1 RCT, 43,783 participants); BBV152: 0.65, 95% CI 0.43 to 0.97; 1 RCT, 25,928 participants). In each of these, the likely absolute difference in effects was fewer than 5/1000 participants. Evidence for SAEs is uncertain for BNT162b2, CoronaVac, BBIBP‐CorV, and NVX‐CoV2373 compared to placebo (RR: BNT162b2: 1.30, 95% CI 0.55 to 3.07; 2 RCTs, 46,107 participants; CoronaVac: 0.97, 95% CI 0.62 to 1.51; 4 RCTs, 23,139 participants; BBIBP‐CorV: 0.76, 95% CI 0.54 to 1.06; 1 RCT, 26,924 participants; NVX‐CoV2373: 0.92, 95% CI 0.74 to 1.14; 4 RCTs, 38,802 participants). For the evaluation of heterologous schedules, booster doses, and efficacy against variants of concern, see main text of review. Authors' conclusions Compared to placebo, most vaccines reduce, or likely reduce, the proportion of participants with confirmed symptomatic COVID‐19, and for some, there is high‐certainty evidence that they reduce severe or critical disease. There is probably little or no difference between most vaccines and placebo for serious adverse events. Over 300 registered RCTs are evaluating the efficacy of COVID‐19 vaccines, and this review is updated regularly on the COVID‐NMA platform (covid-nma.com). Implications for practice Due to the trial exclusions, these results cannot be generalized to pregnant women, individuals with a history of SARS‐CoV‐2 infection, or immunocompromized people. Most trials had a short follow‐up and were conducted before the emergence of variants of concern. Implications for research Future research should evaluate the long‐term effect of vaccines, compare different vaccines and vaccine schedules, assess vaccine efficacy and safety in specific populations, and include outcomes such as preventing long COVID‐19. Ongoing evaluation of vaccine efficacy and effectiveness against emerging variants of concern is also vital.

Melanie Marti

Papers

Vaccine hesitancy around the globe: Analysis of three years of WHO/UNICEF Joint Reporting Form data-2015-2017.

Global Varicella Vaccine Effectiveness: A Meta-analysis

Assessments of global drivers of vaccine hesitancy in 2014—Looking beyond safety concerns

Response to additional COVID-19 vaccine doses in people who are immunocompromised: a rapid review

Efficacy and safety of COVID‐19 vaccines