# Predicting the Epidemiological Effects in the United Kingdom of Moving from PCV13 to PCV15 in the Routine Pediatric 1 + 1 Vaccination Schedule

## TL;DR

This study compares the public health impact of using PCV15 versus PCV13 vaccines in the UK's pediatric vaccination schedule and finds PCV15 leads to lower disease rates.

## Contribution

The study evaluates the epidemiological effects of switching from PCV13 to PCV15 under a 1 + 1 dosing schedule in the UK.

## Key findings

- PCV15 under a 1 + 1 schedule led to a 6.0% lower IPD incidence than PCV13 in the overall population after 20 years.
- PCV13 under a 1 + 1 schedule caused an 11.1% increase in IPD incidence in children under 2 years old.
- PCV15 showed a 3.5% increase in IPD incidence in children under 2 years old compared to pre-vaccination levels.

## Abstract

Background/Objectives: Pneumococcal conjugate vaccines (PCVs) were first introduced in the pediatric UK National Immunization Programme (NIP) in 2006 and subsequently led to a significant decline in invasive pneumococcal disease (IPD). In 2020, the UK NIP reduced the pediatric PCV dosing schedule from two infant doses and one toddler dose (2 + 1) to one infant dose and one toddler dose (1 + 1). This analysis evaluated the public health impact of pediatric vaccination with PCV15 versus PCV13 under a 1 + 1 schedule. Methods: A population-level compartmental model was previously adapted to the UK setting. The impact on the IPD incidence of vaccination with PCV15 versus PCV13 under a 1 + 1 schedule was evaluated over a 20-year time horizon. The uncertainty regarding the vaccine efficacy (VE) of PCV13 and PCV15 under a 1 + 1 schedule was investigated through a probabilistic sensitivity analysis, i.e., the PCV VE under a 1 + 1 schedule was assumed to be 0–24% lower than the PCV VE under a 2 + 1 schedule. Results: Relative to the initial IPD incidence, vaccination with PCV13 and PCV15 under a 1 + 1 schedule resulted in the IPD incidence in children <2 years old increasing by 11.1% (95% region: 8.4–14.5%) and 3.5% (0.2–7.7%), respectively, over the time horizon. At the end of the time horizon, in the overall population, PCV15 would lead to a 6.0% lower IPD incidence than PCV13 (10.70 IPD cases per 100,000 versus 11.38 per 100,000, respectively). Conclusions: Switching from PCV13 to PCV15 for routine pediatric vaccinations under the 1 + 1 dosing schedule in the UK led to a lower IPD incidence in both the pediatric and overall populations.