# Epidemiology of 3 Vaccine-Preventable Infectious Diseases Within US Immigration Detention Centers

## TL;DR

This study analyzed the spread of influenza, mumps, and hepatitis A in US immigration detention centers from 2019 to 2023, finding frequent outbreaks linked to crowding and recommending measures like vaccination and decongregation to reduce transmission.

## Contribution

The study provides the first detailed epidemiological analysis of vaccine-preventable diseases in US immigration detention centers, highlighting seasonal and facility-specific outbreak patterns.

## Key findings

- Influenza had the highest case count (2035 cases) and showed strong seasonal variation, with December as the peak month.
- Mumps and hepatitis A also showed seasonal trends, with outbreaks occurring across multiple facilities.
- No significant geospatial clusters were found, but facility-level case rates varied widely.

## Abstract

What were the burden and transmission patterns of influenza, mumps, and hepatitis A in US Immigration and Customs Enforcement detention facilities from 2019 to 2023, and what risks did they pose to detained migrants and staff?

This case series of 20 facilities found that influenza (2035 cases), mumps (252 cases), and hepatitis A (486 cases) were all prevalent with varying seasonality and multiple facility outbreaks, reflecting the risk profiles for respiratory and enteric infectious diseases of persons entering detention.

On the basis of these findings, decongregation, control of facility crowding, and vaccination programs are recommended approaches to reduce transmission risks for incarcerated migrants and facility employees.

This case series examines epidemiological patterns of 3 vaccine-preventable diseases within US Immigration and Customs Enforcement facilities.

Migrants detained by US Immigration and Customs Enforcement (ICE) are at risk of preventable infections from crowding and limited health care. Postpandemic risk remains unclear as detention increases.

To assess epidemiological patterns of 3 vaccine-preventable diseases within ICE facilities.

This case series study examined data from January 2019 through October 2023 from ICE facilities managed by ICE Health Services Corp during the study period. All cases of influenza, mumps, and hepatitis A among persons detained in reporting ICE facilities were included.

Diagnosis of influenza, mumps, or hepatitis A during ICE detention.

The primary outcomes were monthly case counts and estimated case rates (per 100 000 person-months), outbreak occurrence and duration, and seasonal and geospatial patterns. Outbreaks were defined as 3 or more cases within a facility over at least 1 month. Seasonal variation was assessed through variations in mean monthly case rates across years with analysis of variance, and Tukey tests were used to compare monthly pairwise permutations for statistical significance. Geospatial trends were evaluated using global and local Moran I analyses of annual facility-level case rates.

From 2019 to 2023, at a total of 20 ICE facilities, there were 2035 influenza cases (mean [SD] age, 33.1 [10.8] years; 1804 [88.6%] men), with a mean of 35.1 cases monthly (range, 0.0-276.0 cases monthly). The mean facility-level monthly case rate was 17.3 cases per 100 000 persons (range, 0.0-720.0 cases per 100 000 persons), lower than national rates. December had the highest case rate (mean [SD], 59.4 [142.0] cases per 100 000 persons) and September the lowest (mean [SD], 6.1 [11.9] cases per 100 000 persons), paralleling national trends. Across 15 facilities, 79 outbreaks occurred involving 1739 cases with a mean duration of 2.5 months (range, 1.0-13.0 months). For mumps, 252 cases were reported (mean [SD] age, 34.3 [9.2] years; 235 [93.3%] men), with a mean of 4.3 cases monthly (range, 0.0-61.0 cases monthly). The mean facility-level monthly case rate was 1.5 cases per 100 000 persons (range, 0.0-160.2 cases per 100 000 persons). June had the highest mean case rate (3.1 cases per 100 000 persons) and February the lowest (0.1 cases per 100 000 persons); 16 outbreaks across 8 facilities involved 177 cases with a mean duration of 1.8 months (range, 1.0-6.0 months). For hepatitis A, there were 486 reported cases (mean [SD] age, 39.2 [10.8] years; 408 [84.0%] men), with a mean of 8.4 cases monthly (range, 0.0-40.0 cases monthly). The mean facility-level monthly case rate was 6.0 cases per 100 000 persons (range, 0.0-273.4 cases per 100 000 persons). July had the highest mean case rate (13.8 cases) and November the lowest (2.3 cases); 33 outbreaks across 11 facilities involved 158 cases with a mean duration of 1.2 months (range, 1.0-2.0 months). No geospatial clusters were found.

This case series found that vaccine-preventable infectious disease burden among individuals detained by ICE varied by season and facility. Mitigation could include decongregation, reduced crowding, vaccinations, and improved infection control procedures to protect migrants and staff.