# Routine immunization intensification, vaccination campaigns, and measles transmission in Southern Nigeria

## TL;DR

The paper compares the impact of large vaccination campaigns and a targeted routine immunization on measles transmission in Southern Nigeria.

## Contribution

A novel approach using stochastic transmission models to estimate measles susceptibility and quantify intervention impacts.

## Key findings

- The 2019 routine immunization intensification had a transmission impact comparable to larger campaigns.
- Vaccines in the 2019 effort were more than twice as likely to reach susceptible children.
- The study highlights the importance of disentangling immunity sources in real-world epidemiology.

## Abstract

In this paper, we compare—in terms of their estimated effects on disease transmission—Southern Nigeria’s large-scale measles vaccination campaigns since 2010 to a unique, more targeted routine immunization intensification that happened in 2019. A main focus of the discussion throughout is that quantifying intervention impact in real epidemiologies requires us to disentangle competing, dynamic sources of immunity, including unreported infection. To address this inference challenge, we create a collection of state-level, stochastic transmission models capable of estimating underlying measles susceptibility based on surveillance and survey data. Leveraging these models, we find that the 2019 intensification, despite being restricted in scale to children under 2 years-old, had an effect on transmission comparable to the region’s larger vaccination campaigns targeting children up to 5. This implies that vaccines delivered in that effort were more than twice as likely to reach a susceptible child.