England's Childhood Vaccination Shift Linked to Decreased Booster Uptake and Rising Inequality
A recent study published in The Lancet Regional Health – Europe reveals that a change in England's childhood vaccination strategy, specifically for pneumococcal conjugate vaccines (PCVs), is associated with decreased booster uptake and increased inequality in protection.
PCVs are crucial for targeting diseases caused by Streptococcus pneumoniae and have long been a part of England's routine childhood immunization schedule, evolving from PCV7 to PCV13. In 2020, a significant shift occurred: the vaccine schedule changed from two primary doses and one booster dose (a '2+1' schedule) to one primary dose and one booster dose (a '1+1' schedule).
The UK is currently the only European country employing this 1+1 schedule.
While previous immunogenicity studies suggested potentially comparable protection, the overall effectiveness of this '1+1' schedule hinges critically on timely booster uptake. This change also coincided with broader disruptions, notably the COVID-19 pandemic, which complicated the interpretation of vaccination patterns post-implementation.
Declining Vaccination Coverage
Historically, PCVs led to stable and reduced vaccine-type (VT) invasive pneumococcal disease (IPD) rates across all age groups in England within four years of introduction. However, recent trends show a decline in protection.
National PCV booster coverage at 24 months, which peaked at 92.5% in 2012-13, has declined to 88.2% in 2023-24, falling below the World Health Organization's 95% target. The mean gap between primary PCV dose uptake and booster coverage at 24 months increased from 2.32% under the '2+1' schedule to 4.79% under the '1+1' schedule. This decline aligns with broader pandemic-related drops in vaccine coverage but may also reflect the impact of the schedule change itself.
Widening Deprivation-Related Inequalities
The decline in booster coverage disproportionately affected deprived communities. The gap in PCV booster coverage between the least and most deprived quintiles notably increased from 2-3% before 2020 to 4-6% afterward. London, with its diverse demographics, exhibited particularly low booster retention rates, with Hackney recording a nadir of 65.5% after 2020.
Pre-existing data already indicated a higher burden of IPD in more deprived populations.
An incidence of 13.6 per 100,000 was observed among the most deprived, compared to 7 per 100,000 in the least deprived.
Reduced booster uptake rates, according to model-based estimates, suggest a higher susceptibility to VT IPD in recent cohorts, especially in deprived areas. This susceptibility ranges from 22.4% to 47.8% between the least and most deprived local authorities.
Implications for Public Health
The study suggests that the revised PCV schedule could risk impacting program effectiveness if high and equitable booster uptake is not maintained. Ensuring universal booster uptake is critical, and the widening gap in coverage between socioeconomic groups may contribute to a higher and more unequal VT IPD burden. The success of the '1+1' schedule depends on sustained equitable, high booster uptake, necessitating focused support and improved follow-up systems for vulnerable populations.