Invasive pneumococcal disease (IPD) among people experiencing homelessness (PEH) is not well understood.
We investigated age-adjusted IPD incidence and serotype distribution among adult PEH compared to the general adult population in Anchorage, Alaska from 2005-2018. We calculated IPD incidence per 100,000 person-years using statewide IPD surveillance of pneumococcal sterile site isolates, Census data, and the Anchorage Point in Time count of homeless persons. We examined incidence rate ratios and risk differences using Poisson exact, Chi square and Fisher’s exact tests.
In 2012, PEH accounted for 0.4% of the adult population, but 14.4% of IPD. Compared to the adult population, PEH were 32.5 (95% CI 25.7-41.2) times as likely to have IPD and 34.2 (26.6-44.0) times as likely to have IPD with pneumonia. Compared to the general population with IPD, PEH with IPD were younger (mean age 48.6 vs. 56.7, P<.01), and more likely to abuse alcohol (82.4% vs. 25.1%, P<.01), but not different in the proportion with non-PCV13 serotypes (92.9% vs. 88.7%, P= 0.25). Non-PCV13 serotypes among PEH with IPD included serotype 20 (18.6%), 31 (14.0%), 12F (11%), 16F (9.3%) and 22F/6C/9N (7.0%).
Interventions are warranted for adult PEH who bear a disproportionate burden of IPD in Anchorage.