Pneumococcal Disease Among People Experiencing Homelessness in El Paso County, 2022

People experiencing homelessness are at higher risk of invasive pneumococcal disease (IPD), a serious bacterial infection of the blood or other normally sterile sites, because of underlying health conditions and risk factors. Homelessness alone does not call for pneumococcal vaccination under current Advisory Committee on Immunization Practices (ACIP) guidance: one dose of 20-valent or 15-valent conjugate vaccine (PCV20 or PCV15) is recommended for adults 65 and over, and for those 19–64 with certain conditions or risk factors, who have not had one.

The cluster

On November 29, 2022, a hospital told El Paso County Public Health of three IPD cases among people experiencing homelessness, all falling ill within one week. The department began active surveillance at every local hospital, looking for cases in adults experiencing homelessness from November 1, 2022, to January 28, 2023.

It found 12:

• six used housing and social services at the same shelter;
• nine were men and eight were under 50;
• all had bacteria in the blood, and nine also had pneumonia;
• ten were hospitalised, for a median of 9 days (3 to 14); none died;
• four also had a respiratory virus (SARS-CoV-2, rhinovirus, RSV or human metapneumovirus);
• risk factors included substance abuse (nine), smoking (five), alcoholism (three) and diabetes (one).

CDC typed the bacteria from 10 patients: seven were serotype 4, but genome sequencing showed most of those were not closely related, so this was a cluster of several strains rather than one outbreak strain. The others were serotypes 8, 9N and 19F; 90% of the typed isolates (all but 9N) are types PCV20 covers.

The response

Weekly IPD cases among people experiencing homelessness, and the five vaccination clinics, El Paso County, November 2022–February 2023. CDC.

Fifteen days after the first report, the department held the first of five vaccination clinics at three sites serving people experiencing homelessness, without waiting for the typing results, and gave 87 doses of PCV20, offered to any adult experiencing homelessness.

No new cases were reported from January 29 to April 15, 2023, though one unvaccinated person from the cluster with several risk conditions fell ill again; one more case came in the week of August 23, 2023.

Lessons

Quick, targeted clinics open to all adults experiencing homelessness got vaccine to this population efficiently. Crowding, substance use, chronic illness and poor access to regular health care and vaccination put them at higher risk, and vaccination coverage among younger adults who qualify because of risk conditions has been low and uneven. The authors conclude that for people experiencing homelessness who have a condition for which ACIP recommends the vaccine, pneumococcal vaccination should be standard care.

Sources

• Callaway J, Durbin K, Zachary H, et al. "Notes from the Field: A Cluster of Multi-Strain Invasive Pneumococcal Disease Among Persons Experiencing Homelessness and Use of Pneumococcal Conjugate Vaccine — El Paso County, Colorado, 2022," MMWR. https://www.cdc.gov/mmwr/volumes/72/wr/mm7246a5.htm