# The impact of introducing meningococcal C/ACWY booster vaccination among adolescents in Germany: a dynamic transmission modelling study

## TL;DR

This study models how adding meningococcal booster vaccines for adolescents in Germany could slightly reduce invasive meningococcal disease cases, but with uncertain long-term effectiveness due to potential serogroup replacement.

## Contribution

The study introduces a dynamic transmission model to evaluate adolescent meningococcal booster vaccination strategies in Germany, including serogroup replacement analysis.

## Key findings

- Introducing MenC or MenACWY boosters prevents an estimated 5–8 IMD cases annually on average.
- Number-needed-to-vaccinate to prevent one IMD case is 91,000–140,000, with higher numbers for preventing sequela or death.
- Serogroup replacement may begin 8–10 years after MenACWY booster introduction, introducing uncertainty in long-term effectiveness.

## Abstract

In Germany, primary vaccination against invasive meningococcal disease (IMD) serogroup C aims to reduce the highest burden of IMD in infants aged 12–23 month. Due to another IMD-peak in adolescents, we modelled the potential impact of introducing adolescent boosters with conjugate meningococcal C or ACWY (MenC/MenACWY) vaccines.

We built an age- and serogroup-structured dynamic-transmission model for Germany, which we calibrated to national surveillance data in 2005–2019. We simulated five vaccination scenarios of either continuing with the current MenC primary vaccination (scenario 1), or additionally introducing MenC or MenACWY boosters at age 13 years (scenarios 2–3) or 16 years (scenarios 4–5). We performed comprehensive sensitivity analyses, including on the protection against carriage and serogroup replacement.

The calibrated model projected for scenario 1 an annual mean of 243 (95%-uncertainty interval: 220–258) expected IMD cases over a 10-year period. Introducing the MenC booster prevented an estimated 5 (3.9–6.7) and the MenACWY booster 8 (6.7–9.1) IMD cases per year on average (scenario 2 and 3). The number-needed-to-vaccinate (NNVs) to prevent one IMD case were 140,000 (100,000-180,000) and 91,000 (76,000-100,000), respectively. To prevent one sequela or death, NNVs were higher (i.e., less efficient). Results were broadly similar for scenarios 4–5. Simulations suggested relevant serogroup replacement starting eight-to-ten years after introducing the MenACWY booster.

Introducing adolescent MenC or MenACWY boosters marginally reduces the expected IMD burden in Germany. Effectiveness and efficiency of evaluated strategies depend on future incidence. The magnitude of future serogroup replacement for the MenACWY vaccine is highly uncertain.

The online version contains supplementary material available at 10.1186/s12879-025-12457-2.