What the Liverpool University Study Reveals
A groundbreaking study led by researchers at the University of Liverpool has uncovered persistent and widening inequalities in the uptake of the pneumococcal conjugate vaccine (PCV) among children in England. Published on April 1, 2026, in The Lancet Regional Health – Europe, the research analyzed over a decade of national vaccination data, highlighting how a schedule simplification from a '2+1' to a '1+1' dosing regimen has failed to bridge socioeconomic gaps. Lead author Praise Ilechukwu and corresponding author Dr. Edward Hill from the Department of Health Data Science emphasize that while primary dose coverage remains stable, booster completion rates have declined, particularly in deprived communities.
This longitudinal analysis draws from the Cover of Vaccination Evaluated Rapidly (COVER) programme, which tracks immunisation coverage quarterly across England. The findings align with broader trends in childhood vaccination disparities, underscoring the need for targeted interventions to protect vulnerable young children from severe pneumococcal diseases like pneumonia, meningitis, and sepsis caused by Streptococcus pneumoniae.
Understanding Pneumococcal Conjugate Vaccine and Its Role in Child Health
The pneumococcal conjugate vaccine (PCV), first introduced in England in 2006 as PCV7 and upgraded to PCV13 in 2010, targets the bacterium Streptococcus pneumoniae, responsible for invasive pneumococcal disease (IPD). This pathogen causes around 5,000 cases of IPD annually in the UK, with children under five at highest risk due to immature immune systems. PCV works by conjugating pneumococcal polysaccharides to a protein carrier, eliciting a strong T-cell dependent immune response that generates long-lasting memory B-cells and antibodies.
Pre-vaccine era data showed IPD incidence in children under two at over 50 per 100,000, dropping by more than 50% post-introduction thanks to direct protection (vaccine effectiveness around 80-90% against vaccine-type IPD) and herd immunity. Yet, despite these gains, serotype replacement and residual cases persist, making equitable uptake crucial for sustained control.
Evolution of the PCV Schedule in England
England's routine childhood immunisation programme initially used a '2+1' PCV13 schedule: doses at 2 and 4 months (8 and 16 weeks), plus a booster at 12 months. This ensured high early protection during peak vulnerability. In January 2020, informed by immunogenicity trials showing comparable antibody levels with one primary dose, the schedule shifted to '1+1': single dose at 3 months (12 weeks) and booster at 12 months. The change aimed to simplify delivery, reduce clinic visits, and align with evidence from carriage studies.
However, the transition coincided with the COVID-19 pandemic, disrupting routines and exacerbating access barriers. UK Health Security Agency (UKHSA) data confirms overall PCV coverage hovered around 90-93%, but granular analysis reveals cracks, especially for boosters reliant on parental follow-through post-infancy.
Methodology: A Robust Data-Driven Approach
The Liverpool team examined COVER data for children turning one and two years old from 2013 to 2025 across 150 upper-tier local authorities, linked to the 2019 Index of Multiple Deprivation (IMD) quintiles. Booster 'gaps'—the percentage point difference between primary and booster coverage—served as the key metric. Trends were segmented pre- (2013-2020) and post-schedule change (2020-2025). Susceptibility to vaccine-type IPD was modeled using uptake data and PCV13 effectiveness estimates (direct VE ~80% for fully vaccinated).
Statistical analysis included slope index of inequality (SII) to quantify deprivation gradients, revealing not just averages but local vulnerabilities masked by national figures.
Uptake Trends Before and After the Schedule Shift
Pre-2020, average 12-month coverage was 93.2%, dropping to 91.2% at 24 months (2.0% gap). Post-change, 12-month held at 93.3%, but 24-month fell to 89.0% (4.4% gap)—more than double. Mean national booster gaps rose from 2.32% to 4.79%. The modal gap shifted from 1-2% to 2.5-3%, with extremes exceeding 12% post-2020.Full study details here.
COVID disruptions peaked gaps in 2020-2022, with slower recovery in deprived areas, confirming the '1+1' reliance on booster completion amplifies risks when systems falter.
Photo by Spencer Davis on Unsplash
Socioeconomic Disparities: Widening Gaps by Deprivation
IMD quintile analysis showed consistent gradients: pre-2020, least deprived (Q1) ~94% booster coverage vs. most deprived (Q5) ~90% (2-4 pp gap). Post-2020, Q1 recovered to ~92-93%, Q5 lagged at ~87-89% (4-6 pp gap). SII worsened, with deprived children facing compounded vulnerability. Susceptibility modeling estimated 22-48% VT-IPD risk locally, highest in Q3/Q5.
- Q1 (least deprived): Lowest susceptibility, stable protection.
- Q5 (most deprived): Highest susceptibility peaks >30%, volatile post-2020.
- Gap expansion: 2-3% to 4-6 pp between extremes.
These patterns echo UKHSA's 2025 equity audit, noting 3.7 pp national PCV inequality.UKHSA report.
Regional Variations and Disease Susceptibility Risks
Geographic hotspots emerged: North West, West Midlands, London showed largest gaps (up to 12%+), with susceptibility 30-48%. Southern authorities fared better (20-30%). Modeling predicts disproportionate IPD burden in deprived urban pockets, eroding herd immunity for elderly too.
London boroughs drove national deterioration, linking to access barriers like transport, clinic availability, and trust issues.
Parallels with Broader Childhood Vaccine Inequalities
This PCV focus mirrors a prior Liverpool study (BMJ, 2024) on five vaccines (MMR1/2, rotavirus, PCV booster, 6-in-1) from 2019-23. SII worsened across all: MMR2 from -9.6% to -13.4%; PCV booster -7.9% to -9.7%. Susceptible measles cases surged 20-fold in deprived groups. Regional lows: London, North West.Related BMJ paper.
Insights from Liverpool Researchers
Dr. Edward Hill: “National averages mask local vulnerabilities. Granular data enables precise targeting.” Praise Ilechukwu: “Deprived children remain more vulnerable to pneumonia and meningitis.” Prof. Neil French: “Monitor booster gaps by deprivation routinely.” Dr. Dan Hungerford: “Address social determinants via flexible access and outreach.”
These voices from Liverpool's Institutes of Population Health and Infection highlight interdisciplinary expertise driving policy-relevant research.
Public Health Implications and Disease Burden
Persistent gaps risk resurgent IPD: Pre-PCV, child mortality ~10%; now averted thousands yearly, but replacement serotypes (e.g., 3, 18% cases) loom. Widening disparities could cascade via lost herd effects, hitting vulnerable adults. Economic toll: IPD hospitalization £millions annually.
Pathways to Equity: Recommended Interventions
Solutions include:
- Enhanced call-recall systems with SMS/app reminders.
- Community outreach in deprived areas (pop-up clinics, trusted leaders).
- Routine IMD-stratified monitoring as KPI.
- Flexible access: Evenings/weekends, home visits.
- Tailored education countering 'booster hesitancy'.
Timely amid House of Lords inquiry on vaccination decline.
Future Outlook for PCV Programme and Research
With higher-valency PCVs (PCV20/21) horizon, maintaining equity vital. Liverpool's work positions UK unis as leaders in vaccine equity research. Ongoing NIHR-funded efforts promise data-driven reversals, ensuring no child left unprotected.
