The contagious nature of a vaccine scare: How the introduction of HPV vaccination lifted and eroded MMR vaccination in Denmark

Identifying characteristics that enable resilient immunisation programmes: a scoping review

OBJECTIVES

The COVID-19 pandemic highlighted the fragility of immunisation programmes and resulted in a significant reduction in vaccination rates, with increasing vaccine-preventable disease outbreaks consequently reported. These vulnerabilities underscore the importance of resilient immunisation programmes to ensure optimal performance during crises. To date, a framework for assessing immunisation programme resilience does not exist. We conducted a scoping review of immunisation programmes during times of crisis to identify factors that characterise resilient immunisation programmes, which may inform an Immunisation Programme Resilience Tool.

DESIGN

Scoping review design followed the Arksey and O'Malley framework, and manuscript reporting followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Scoping Reviews guidelines.

DATA SOURCES

CINAHL, CENTRAL, Embase, Google Scholar, MEDLINE, PsycINFO and Web of Science and databases were searched between 1 January 2011 and 2 September 2023. Citation searching of identified studies was also performed.

ELIGIBILITY CRITERIA

We included primary empirical peer-reviewed studies that discussed the resilience of immunisation programme to crises, shocks or disruptions.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers screened records and performed data extraction. We extracted data on study location and design, crisis description, and resilience characteristics discussed, and identified evidence gaps in the literature. Findings were synthesised using tabulation and an evidence gap map.

RESULTS

Thirty-seven studies met the eligibility criteria. These studies captured research conducted across six continents, with most concentrated in Africa, Asia and Europe. One study had a randomised controlled trial design, while 36 studies had observational designs (15 analytical and 21 descriptive). We identified five characteristics of resilient immunisation programmes drawing on the Health System Resilience Index (Integration, Awareness, Resource Availability and Access, Adaptiveness and Self-regulation) and several evidence gaps in the literature.

CONCLUSIONS

To our knowledge, no immunisation programme resilience tool exists. We identified factors from the Health System Resilience Index coupled with factors identified through primary empirical evidence, which may inform development of an immunisation programme resilience tool.

Vaccine rhetoric on social media and COVID-19 vaccine uptake rates: A triangulation using self-reported vaccine acceptance

The primary goal of this study is to examine the association between vaccine rhetoric on Twitter and the public's uptake rates of COVID-19 vaccines in the United States, compared to the extent of an association between self-reported vaccine acceptance and the CDC's uptake rates. We downloaded vaccine-related posts on Twitter in real-time daily for 13 months, from October 2021 to September 2022, collecting over half a billion tweets. A previously validated deep-learning algorithm was then applied to (1) filter out irrelevant tweets and (2) group the remaining relevant tweets into pro-, anti-, and neutral vaccine sentiments. Our results indicate that the tweet counts (combining all three sentiments) were significantly correlated with the uptake rates of all stages of COVID-19 shots (p < 0.01). The self-reported level of vaccine acceptance was not correlated with any of the stages of COVID-19 shots (p > 0.05) but with the daily new infection counts. These results suggest that although social media posts on vaccines may not represent the public's opinions, they are aligned with the public's behaviors of accepting vaccines, which is an essential step for developing interventions to increase the uptake rates. In contrast, self-reported vaccine acceptance represents the public's opinions, but these were not correlated with the behaviors of accepting vaccines. These outcomes provide empirical support for the validity of social media analytics for gauging the public's vaccination behaviors and understanding a nuanced perspective of the public's vaccine sentiment for health emergencies.

Sibling spillovers and the choice to get vaccinated: Evidence from a regression discontinuity design

We investigate the effects of introducing population-wide free-of-charge Human Papillomavirus (HPV) vaccination programs on the targeted adolescent cohorts and their siblings. For identification, we rely on regression discontinuity designs and high-quality Danish administrative data to exploit that date of birth determines program eligibility. We find that the programs increased the HPV vaccine take-up of both the targeted children (53.2 percentage points for girls and 36.0 percentage points for boys) and their older same-sex siblings (4.5 percentage points for sisters and 3.5 percentage points for brothers). We show that while the direct effects of the programs reduced HPV vaccine take-up inequality, the spillover effects, in contrast, contributed to an increase in vaccine take-up inequality highlighting the potential importance of spillover effects in the determination of distributional consequences of public health programs. Finally, we find some evidence of cross-vaccine spillovers.

Let's call! Using the phone to increase vaccine acceptance

In the context of the COVID-19 pandemic, we develop and test experimentally three phone-based interventions to increase vaccine acceptance in Mozambique. The first endorses the vaccine with a simple positive message. The second adds the activation of social memory on the country's success in eradicating wild polio with vaccination campaigns. The third further adds a structured interaction with the participant to develop a critical view toward misleading information and minimize the sharing of fake news. We find that combining the endorsement with the stimulation of social memory and the structured interaction increases vaccine acceptance and trust in institutions.

Reminder design and childhood vaccination coverage

A major policy concern across public vaccination programs is non-compliance. Exploiting Danish population data and three national reforms in regression discontinuity designs, we document the effects of reminders for childhood vaccination coverage. Retrospective reminders are primarily effective for families with small children and when sent out close to the recommended vaccination age. Digital and postal reminders are equally effective. Prospective reminders increase timely vaccinations in later childhood and help reaching high coverage for new vaccines in increasingly complex vaccination programs. While reminders prompt additional preventive care for focal children, we find no spillovers to other health behaviors or relatives.

COVID-19 Vaccine Confidence Mediates the Relationship between Health Literacy and Vaccination in a Diverse Sample of Urban Adults

We sought to analyze the relationship between health literacy, confidence in COVID-19 vaccines, and self-reported vaccination. We hypothesized that the relationship between health literacy and vaccination would be mediated by vaccine confidence. We recruited (N = 271) English- and Spanish-speaking adults in Boston and Chicago from September 2018 to September 2021. We performed a probit mediation analysis to determine if confidence in COVID-19 vaccines and health literacy predicted self-reported vaccination. We hypothesized that the relationship between health literacy and vaccination would be mediated by vaccine confidence. Participants were on average 50 years old, 65% female, 40% non-Hispanic Black, 25% Hispanic, and 30% non-Hispanic White; 231 (85%) reported at least one COVID-19 vaccination. A higher mean vaccine confidence score (t = -7.9, p < 0.001) and higher health literacy (t = -2.2, p = 0.03) were associated with vaccination, but only vaccine confidence predicted vaccination in a multivariate model. Vaccine confidence mediated the relationship between health literacy and COVID-19 vaccination (mediated effects: 0.04; 95% CI [0.02, 0.08]). We found that using a simple tool to measure vaccine confidence identified people who declined or delayed COVID-19 vaccination in a diverse sample of adults with varying levels of health literacy. Simple short survey tools can be useful to identify people who may benefit from vaccine promotion efforts and evidence-based communication strategies.

Measles, mumps, and rubella vaccine at age 6 months and hospitalisation for infection before age 12 months: randomised controlled trial

OBJECTIVE

To test for potential non-specific effects of an additional, early measles, mumps, and rubella (MMR) vaccine at age 5-7 months on risk of infection related hospitalisation before age 12 months.

DESIGN

Randomised, double blinded, placebo controlled trial.

SETTING

Denmark, a high income setting with low exposure to MMR.

PARTICIPANTS

6540 Danish infants aged 5 to 7 months.

INTERVENTIONS

Infants were randomly allocated 1:1 to intramuscular injection with standard titre MMR vaccine (M-M-R VaxPro) or placebo (solvent only).

MAIN OUTCOME MEASURES

Hospitalisations for infection, defined as all hospital contacts of infants referred from primary care for hospital evaluation and with an infection diagnosed, analysed as recurrent events, from randomisation to 12 months of age. In secondary analyses implications of censoring for date of subsequent diphtheria, tetanus, pertussis, polio, Haemophilus influenzae type B, and immunisation with pneumococci conjugate vaccine (DTaP-IPV-Hib+PCV), potential effect modification by sex, prematurity (<37 weeks' gestation), season, and age at randomisation were tested, and the secondary outcomes of hospitalisations ≥12 hours and antibiotic use were evaluated.

RESULTS

6536 infants were included in the intention-to-treat analysis. 3264 infants randomised to MMR vaccine experienced 786 hospitalisations for infection before age 12 months compared with 762 for the 3272 infants randomised to placebo. In the intention-to-treat analysis the rate of hospitalisations for infection did not differ between the MMR vaccine and placebo groups (hazard ratio 1.03, 95% confidence interval 0.91 to 1.18). For infants randomised to MMR vaccine compared with those randomised to placebo, the hazard ratio of hospitalisations for infection with a duration of at least 12 hours was 1.25 (0.88 to 1.77), and for prescriptions of antibiotics was 1.04 (0.88 to 1.23). No significant effect modifications were found by sex, prematurity, age at randomisation, or season. The estimate did not change when censoring at the date infants received DTaP-IPV-Hib+PCV after randomisation (1.02, 0.90 to 1.16).

CONCLUSION

Findings of this trial conducted in Denmark, a high income setting, do not support the hypothesis that live attenuated MMR vaccine administered early to infants aged 5-7 months decreases the rate of hospitalisations for non-targeted infection before age 12 months.

TRIAL REGISTRATION

EU Clinical Trials Registry EudraCT 2016-001901-18 and ClinicalTrials.gov NCT03780179.

First hepatitis B vaccine uptake in neonates prior to and during the COVID-19 pandemic

Introduction

Routine vaccination for hepatitis B is recommended at birth, and most infants should be vaccinated within 24 h of life. Historically, vaccination rates have been less than ideal, and routine vaccination has been further complicated by the COVID-19 pandemic, with decreased uptake of many vaccines. This retrospective study assessed hepatitis B vaccination rates at birth before and after the start of the COVID-19 pandemic and explored the factors associated with lower vaccination rates.

Methods

Infants born at a single academic medical center in Charleston, South Carolina from November 1, 2018 through June 30, 2021 were identified. Infants were excluded if they died or received ≥ 7 days of systemic steroid therapy within the first 37 days of life. Maternal and infant baseline characteristics and uptake of the first hepatitis B vaccine during hospital admission were recorded.

Results

A total of 7808 infants were included in the final analysis, with an overall vaccine uptake of 91.6 %. Of the 3880 neonates in the pre-pandemic group, 3583 (92.3 %) were vaccinated, versus 3571 (90.9 %) of 3928 neonates in the pandemic group (rate difference = 1.4 %; 95 % confidence interval −2.8 % to 5.7 %, p = 0.52). Factors independently associated with lower vaccine uptake included being of non-Hispanic white race, born to a married mother, birth weight < 2 kg, and parental refusal of erythromycin eye ointment at birth.

Conclusion

The COVID-19 pandemic did not significantly affect the uptake of inpatient neonatal hepatitis B vaccination. Several patient-specific factors were associated with suboptimal vaccination rates in this population.

Standing alone: experiences of vaccine-hesitant Danish healthcare professionals during COVID-19

AIM

The aim of the study was to explore the experiences of Danish healthcare professionals who were hesitant about the COVID-19 vaccine.

METHODS

Interviews were conducted over the telephone in January and February 2021.

RESULTS

Healthcare professionals experienced the need to avoid impossible conversations about vaccine hesitancy with their colleagues. They felt a lack of knowledge of long-term experience with the vaccine and a need to balance trust in themselves and the authorities.

CONCLUSIONS

Healthcare professionals who were hesitant towards the COVID-19 vaccine felt they had to keep their concerns to themselves and felt isolated and pressured by their managers. This study is especially important for managers, who must ensure a trusting working environment in which employees can discuss their concerns without feeling pressured.

Partisan Differences in Legislators' Discussion of Vaccination on Twitter During the COVID-19 Era: Natural Language Processing Analysis

BACKGROUND

The COVID-19 era has been characterized by the politicization of health-related topics. This is especially concerning given evidence that politicized discussion of vaccination may contribute to vaccine hesitancy. No research, however, has examined the content and politicization of legislator communication with the public about vaccination during the COVID-19 era.

OBJECTIVE

The aim of this study was to examine vaccine-related tweets produced by state and federal legislators during the COVID-19 era to (1) describe the content of vaccine-related tweets; (2) examine the differences in vaccine-related tweet content between Democrats and Republicans; and (3) quantify (and describe trends over time in) partisan differences in vaccine-related communication.

METHODS

We abstracted all vaccine-related tweets produced by state and federal legislators between February 01, 2020, and December 11, 2020. We used latent Dirichlet allocation to define the tweet topics and used descriptive statistics to describe differences by party in the use of topics and changes in political polarization over time.

RESULTS

We included 14,519 tweets generated by 1463 state legislators and 521 federal legislators. Republicans were more likely to use words (eg, "record time," "launched," and "innovation") and topics (eg, Operation Warp Speed success) that were focused on the successful development of a SARS-CoV-2 vaccine. Democrats used a broader range of words (eg, "anti-vaxxers," "flu," and "free") and topics (eg, vaccine prioritization, influenza, and antivaxxers) that were more aligned with public health messaging related to the vaccine. Polarization increased over most of the study period.

CONCLUSIONS

Republican and Democratic legislators used different language in their Twitter conversations about vaccination during the COVID-19 era, leading to increased political polarization of vaccine-related tweets. These communication patterns have the potential to contribute to vaccine hesitancy.

Who knows best? Health risks and digital media engagement in Discourses relating to human papillomavirus vaccination

In Denmark, parents have needed to deal with inconsistent presentations of risk regarding the human papillomavirus (HPV) vaccination. This has complicated the parents' task of making a decision about having their daughters vaccinated. In this article, I analyse how Danish parents engage with digital media when making this decision. The results are based on interviews with 18 Danish parents of girls aged 10-13 years old. In my analysis of the interviews, I found that parents align with one of two Discourses when engaging with digital media in relation to HPV vaccination: one centralised and one decentralised. In the centralised Discourse, parents leave it up to other actors such as health authorities to manage the risks of vaccination, thus limiting the experienced need to engage with digital media; in the decentralised Discourse, however, parents themselves assess potential risks, thereby increasing the need to engage with digital media. As a result, I discuss why some parents can consider it necessary to struggle to engage in literacies when making decisions about complex health topics, even when there are clear government recommendations.

Vaccine Hesitancy and Differential Susceptibility to Media Coverage: A Critical Documentary Led to Substantial Reductions in Human Papillomavirus Vaccine Uptake in Denmark

OBJECTIVES

To investigate whether negative media coverage of the human papillomavirus (HPV) vaccine led to a decrease in the uptake of the first dose of the HPV vaccine (HPV1) in Denmark and, importantly, whether some groups of individuals were more susceptible to negative media coverage.

METHODS

We measured HPV vaccine uptake of 12-year-old girls born in 2001 to 2004 using Danish administrative data. A quasi-experimental design was employed to assess whether a documentary that was critical of the HPV vaccine and aired in March 2015 affected HPV uptake.

RESULTS

The documentary led to a quick and substantial decrease in the monthly propensity to vaccinate, which dropped 3 percentage points-or about 50%-in response to the documentary. Responses differed substantially across subgroups, and girls from families with high socioeconomic status (SES) were more susceptible to the negative media coverage.

CONCLUSIONS

Susceptibility to negative media coverage varied substantially across subgroups, highlighting the need for policy makers to appropriately target and differentiate initiatives to improve vaccine compliance rates.

Inattention or reluctance? Parental responses to vaccination reminder letters

This paper studies non-adherence in the Danish Childhood Vaccination Program using a nationwide introduction of a vaccination reminder letter policy and administrative data from 2011-2017. First, I provide causal estimates of how the reminder letter policy affects vaccination adherence using a Regression Discontinuity Design (RDD). Second, I link parental responses to the reminder letter to parents' causes for being non-adherent. I find that the reminder letter policy positively affects adherence. However, 72% of non-adherent parents are non-responsive to the reminder letter indicating that reluctance and not inattention is the leading cause for non-adherence. Thus, other policies beyond reminder letters - such as mandatory vaccination laws - are necessary to substantially increase vaccination coverage.