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Unrepresentative big surveys significantly overestimated US vaccine uptake.

ABSTRACT: Surveys are a crucial tool for understanding public opinion and behaviour, and their accuracy depends on maintaining statistical representativeness of their target populations by minimizing biases from all sources. Increasing data size shrinks confidence intervals but magnifies the effect of survey bias: an instance of the Big Data Paradox¹. Here we demonstrate this paradox in estimates of first-dose COVID-19 vaccine uptake in US adults from 9 January to 19 May 2021 from two large surveys: Delphi-Facebook^2,3 (about 250,000 responses per week) and Census Household Pulse⁴ (about 75,000 every two weeks). In May 2021, Delphi-Facebook overestimated uptake by 17 percentage points (14-20 percentage points with 5% benchmark imprecision) and Census Household Pulse by 14 (11-17 percentage points with 5% benchmark imprecision), compared to a retroactively updated benchmark the Centers for Disease Control and Prevention published on 26 May 2021. Moreover, their large sample sizes led to miniscule margins of error on the incorrect estimates. By contrast, an Axios-Ipsos online panel⁵ with about 1,000 responses per week following survey research best practices⁶ provided reliable estimates and uncertainty quantification. We decompose observed error using a recent analytic framework¹ to explain the inaccuracy in the three surveys. We then analyse the implications for vaccine hesitancy and willingness. We show how a survey of 250,000 respondents can produce an estimate of the population mean that is no more accurate than an estimate from a simple random sample of size 10. Our central message is that data quality matters more than data quantity, and that compensating the former with the latter is a mathematically provable losing proposition.

SUBMITTER: Bradley VC

PROVIDER: S-EPMC8653636 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundCOVID-19 vaccine hesitancy can lead to reduced vaccine uptake and hinder the safe relaxation of other public health measures. This study aims to explore the factors associated with vaccine hesitancy and uptake among adults before and after the implementation of the COVID-19 vaccination program in Hong Kong.MethodsCross-sectional telephone surveys were conducted every four weeks over a nine-month period from November 2020 through July 2021. Target respondents were Hong Kong resident aged 18 or above and recruited by random-digit dialling. In each survey, responses on COVID-19 vaccine hesitancy and COVID-19 vaccine uptake were collected as primary and secondary outcomes, respectively. Data of potentially associated factors, including socio-demographics, chronic medical conditions, perceived risk of COVID-19, perceived personal efficacy in self-protection, confidence in the government's ability to control the pandemic, compliance with social distancing measures, and confidence in COVID-19 vaccines, were also collected. Multivariable logistic regression models were used to examine the factors associated with COVID-19 vaccine hesitancy at different time points.FindingsTen cross-sectional surveys were conducted, including 7411 respondents. The levels of vaccine hesitancy fluctuated over time. From December 2020 to May 2021, the age group with the highest vaccine hesitancy was young adults 18-34y, while the vaccine hesitancy was highest among adults ≥ 65y in June-July 2021 (Fig. 2C). Our regression analyses (Fig. 3) showed that before and at the beginning of the rollout of the mass vaccination program, there was no statistically significant association between chronic medical conditions and vaccine hesitancy. However, two-five months after the program implementation respondents with chronic medical conditions were more likely to be hesitant. From January to June 2021, higher confidence in the government was associated with lower vaccine hesitancy (Fig. 3). Confidence in COVID-19 vaccines was consistently associated with lower vaccine hesitancy at different stages of the program.InterpretationThe factors associated with COVID-19 vaccine hesitancy changed over time. This study highlighted the importance to monitor temporal changes in COVID-19 vaccine hesitancy and associated factors, and adjust promotion strategies correspondingly to boost vaccination uptake.FundingHealth and Medical Research Fund, Hong Kong.

Project description:ObjectiveIn 2012, recommendations for universal tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination during pregnancy were released. Our objective was to determine if Tdap, influenza, and pneumococcal vaccine uptake during pregnancy changed after the release of the guidelines, and identify factors associated with receiving the Tdap and influenza vaccine after 2012.MethodsWe conducted a retrospective cohort study on pregnant individuals who initiated prenatal care before 20 weeks' gestation between 11/2011-11/2012 ("pre-guideline") and 12/2012-12/2015 ("post-guideline"). Vaccine uptake dates were abstracted from medical records. The pre and post-guideline cohorts were compared to determine if Tdap vaccine uptake and timing improved after the new Tdap guidelines. We additionally examined influenza and pneumococcal vaccine uptake before and after guidelines. Factors associated with receipt of the Tdap and influenza vaccine during pregnancy in the post-guideline cohort were evaluated using multivariable logistic regression models.ResultsOf 2,294 eligible individuals, 1,610 (70.2%) received care in the post-guideline cohort. Among the pre-guideline cohort, 47.4% received Tdap, whereas Tdap uptake increased to 86.1% after the guidelines (p<0.001). Similarly, receiving the Tdap vaccine between the recommended time of 27-36 weeks gestational age improved from 52.5% to 91.8% after the guidelines (p<0.001). Vaccine frequency for influenza improved significantly from 61.2% to 72.0% (p<0.001), while frequency for pneumococcus were low and unchanged. An increased number of prenatal visits was associated with receiving the Tdap and influenza vaccines during pregnancy (respective, aOR 1.09 95% CI 1.05-1.13; aOR 1.50 95% CI 1.17-1.94). Non-Hispanic Black individuals were less likely to receive both the Tdap and influenza vaccines during pregnancy compared to non-Hispanic White individuals (respective, aOR 0.51 95% CI 0.33-0.80; aOR 0.68 95% CI 0.48-0.97).ConclusionsReceipt and timing of Tdap vaccine improved after implementation of the 2012 ACIP guidelines. Receipt of influenza vaccine uptake also improved during the study period, while uptake of the pneumococcal vaccine remained low. Significant racial disparities exist in receipt of Tdap and influenza vaccine during pregnancy.

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Unrepresentative big surveys significantly overestimated US vaccine uptake.

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