Expanded question: Does improved vaccine uptake enhance vaccine effectiveness?

Answered on February 27, 2025
Improved vaccine uptake enhances vaccine effectiveness at the population level by increasing herd immunity and reducing the overall burden of disease. This relationship is well-documented in the medical literature.
For instance, a study published in Clinical Infectious Diseases by Hughes et al. demonstrated that even small increases in vaccine coverage (VC) can lead to substantial reductions in influenza-associated illnesses and hospitalizations. Specifically, a 5% increase in VC could prevent 785,000 additional illnesses and 11,000 hospitalizations during a single influenza season.[1] This indicates that higher vaccine uptake can amplify the overall effectiveness of vaccination programs by reducing disease transmission and protecting vulnerable populations.
Additionally, a systematic review and meta-analysis by Atkinson et al. in the journal Vaccine found that digital interventions to improve vaccine uptake modestly increased the odds of vaccination, further supporting the notion that higher uptake can enhance the overall impact of vaccination efforts.[2]
Moreover, the study by Sah et al. in the Proceedings of the National Academy of Sciences highlighted that even low-efficacy vaccines can be highly impactful when uptake is optimized across different age groups, emphasizing the importance of achieving high coverage to maximize public health benefits.[3]
In summary, increasing vaccine uptake is crucial for enhancing the overall effectiveness of vaccination programs, as it leads to greater herd immunity and a more significant reduction in disease burden.

1.
Projected Population Benefit of Increased Effectiveness and Coverage of Influenza Vaccination on Influenza Burden in the United States.

Hughes MM, Reed C, Flannery B, et al.

Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2020;70(12):2496-2502. doi:10.1093/cid/ciz676.

Leading Journal

Background: Vaccination is the best way to prevent influenza; however, greater benefits could be achieved. To help guide research and policy agendas, we aimed to quantify the magnitude of influenza disease that would be prevented through targeted increases in vaccine effectiveness (VE) or vaccine coverage (VC).

Methods: For 3 influenza seasons (2011-12, 2015-16, and 2017-18), we used a mathematical model to estimate the number of prevented influenza-associated illnesses, medically attended illnesses, and hospitalizations across 5 age groups. Compared with estimates of prevented illness during each season, given observed VE and VC, we explored the number of additional outcomes that would have been prevented from a 5% absolute increase in VE or VC or from achieving 60% VE or 70% VC.

Results: During the 2017-18 season, compared with the burden already prevented by influenza vaccination, a 5% absolute VE increase would have prevented an additional 1 050 000 illnesses and 25 000 hospitalizations (76% among those aged ≥65 years), while achieving 60% VE would have prevented an additional 190 000 hospitalizations. A 5% VC increase would have resulted in 785 000 fewer illnesses (56% among those aged 18-64 years) and 11 000 fewer hospitalizations; reaching 70% would have prevented an additional 39 000 hospitalizations.

Conclusions: Small, attainable improvements in effectiveness or VC of the influenza vaccine could lead to substantial additional reductions in the influenza burden in the United States. Improvements in VE would have the greatest impact in reducing hospitalizations in adults aged ≥65 years, and VC improvements would have the largest benefit in reducing illnesses in adults aged 18-49 years.

2.
Effectiveness of Digital Technologies at Improving Vaccine Uptake and Series Completion - A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Atkinson KM, Wilson K, Murphy MSQ, et al.

Vaccine. 2019;37(23):3050-3060. doi:10.1016/j.vaccine.2019.03.063.

Background: Recent outbreaks and renewed concerns about immunization coverage call for new and effective interventions to improve vaccine uptake. Digital technologies have the potential to help address both suboptimal vaccine uptake and series completion. However, the effectiveness of pushing information and reminders to patients through digital technologies to address vaccination is not known. OBJECTIVE(S): The aim of this study is to determine if digital push interventions are effective in increasing vaccine uptake and series completion compared to non-digital interventions.

Methods: We searched for RCTs where adults or parents of children were eligible for vaccination, the intervention was digital-push and the comparison group was non-digital. We included outcomes of vaccine uptake or series completion. We estimated summary effect sizes, heterogeneity using the χ test and quantified using the I statistic. Where heterogeneity remained significant, we conducted subgroup analyses. We assessed risk of bias, certainty of evidence and publication bias.

Results: The search identified 159 peer-reviewed scientific publications. After review, a total of 12 manuscripts representing 13 empirical studies published between 2012 and 2016 were included. When comparing digital push interventions to non-digital ones, patients had 1.18[1.11,1.25] the odds of receiving vaccination or series completion compared to controls. In parents of children aged 18 and younger, those receiving digital push had a 1.22[1.15,1.30] increased odds compared to controls. Both analyses had high statistical heterogeneity, with I values of 86% and 79% respectively. The risk of bias was low with 10 of 13 studies considered low risk in five or more domains. The certainty of evidence for series completion was very low and for vaccine uptake was assessed to be moderate.

Conclusion: This study provides evidence that digital push technologies have a modest, positive impact on vaccine uptake and series completion compared to non-digital interventions.

3.
Optimizing the Impact of Low-Efficacy Influenza Vaccines.

Sah P, Medlock J, Fitzpatrick MC, Singer BH, Galvani AP.

Proceedings of the National Academy of Sciences of the United States of America. 2018;115(20):5151-5156. doi:10.1073/pnas.1802479115.

Leading Journal

The efficacy of influenza vaccines varies from one year to the next, with efficacy during the 2017-2018 season anticipated to be lower than usual. However, the impact of low-efficacy vaccines at the population level and their optimal age-specific distribution have yet to be ascertained. Applying an optimization algorithm to a mathematical model of influenza transmission and vaccination in the United States, we determined the optimal age-specific uptake of low-efficacy vaccine that would minimize incidence, hospitalization, mortality, and disability-adjusted life-years (DALYs), respectively. We found that even relatively low-efficacy influenza vaccines can be highly impactful, particularly when vaccine uptake is optimally distributed across age groups. As vaccine efficacy declines, the optimal distribution of vaccine uptake shifts toward the elderly to minimize mortality and DALYs. Health practitioner encouragement and concerted recruitment efforts are required to achieve optimal coverage among target age groups, thereby minimizing influenza morbidity and mortality for the population overall.