An intervention of molecular influenza testing along with antiviral treatment for residents of homeless shelters proved feasible but showed no effect on the transmission of influenza virus, according to study findings published in Influenza and Other Respiratory Viruses.

Because people living in homeless shelters face increased risk for influenza, researchers sought to investigate whether an intervention offering point-of-care molecular testing and antiviral treatment for influenza was feasible in this setting and whether the intervention reduced influenza transmission.

The investigators conducted a stepped-wedge clinical trial ( Identifier: NCT04141917) of residents of 14 homeless shelters in Seattle (duration of homelessness: 32% <6 months; 40% >24 months). The primary outcome was monthly influenza virus infections in intervention vs control periods. During control periods, mid-nasal swabs were tested for influenza by reverse transcription polymerase chain reaction (RT-PCR). During intervention periods, staffed influenza-surveillance kiosks at each shelter were used to recruit and screen residents for eligibility, study participants received onsite rapid molecular influenza testing, and those testing positive were offered antiviral treatment (baloxivir or oseltamivir) for influenza if symptom onset was within less than 48 hours.

Trial participants were at least 3 months of age and had new or worsening cough or at least 2 acute respiratory illness (ARI) symptoms within the previous 7 days. Participants were 52% White, 28% Black, and 11% Hispanic/Latinx ethnicity; 8.3% were children and 30.9% were women; 30% had some college and 11% had a Bachelor’s degree; 91% had health insurance; and the median age was 45 years. Study participants were enrolled across 2 influenza seasons from November 2019 through April 2020, and from November 2020 through April 2021 (although the COVID-19 pandemic distorted the results from the latter influenza season, study authors noted). Among all participants, 41% self-reported receiving the current season’s influenza vaccine.

[W]e found that use of a rapid molecular point-of-care test-and-treat strategy for influenza at shelters was feasible, whereas the intervention had no significant effect on influenza incidence.

Across the 2 study periods, researchers noted 1283 ARI incidents in 668 participants (1159 incidents in year 1; 124 in year 2); 37% of these participants subsequently reported symptom onset in less than 48 hours. Influenza virus was found in 51 specimens (4%) using RT-PCR (A=14; B=37). Rapid molecular testing detected 21 influenza virus infections in participants among the 269 intervention-eligible encounters. These 21 participants then received antiviral treatment.

Researchers noted the intervention had no effect on influenza virus transmission (adjusted relative risk, 1.73; 95% CI, 0.50-6.00). After generating genome sequences to evaluate transmission and antiviral resistance for 23 samples, the investigators found that 86% of A(H1N1)pdm09 and 81% of B/Victoria sequences were closely related, suggesting that “inter-shelter transmission was a possibility,” the researchers noted.

Study limitations include underpowered sample sizes, unaccounted-for resident transiency, selection bias, unaccounted-for residents with asymptomatic infections, and subjectivity in self-reported symptoms and illness duration.

“[W]e found that use of a rapid molecular point-of-care test-and-treat strategy for influenza at shelters was feasible, whereas the intervention had no significant effect on influenza incidence,” the researchers concluded. “A majority of RT-PCR influenza-positive participants identified during intervention periods received antiviral treatment (59.4%), suggesting that immediate treatment is feasible,” they added, noting that few shelter residents were prescribed an antiviral prior to study enrollment.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

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