XBB.1.5 mRNA COVID-19 Vaccination and Inpatient or Emergency Department Visits Among Adults Infected with SARS-CoV-2 JN.1 and XBB-Lineage Variants (preprint)

Within a multi-state viral genomic surveillance program, we conducted a case-control analysis comparing prior receipt of XBB.1.5-adapted mRNA vaccination between SARS-CoV-2-infected adults with inpatient/ED visits (proxy for severe illness) vs outpatient visits. Among 6,551 patients from September 2023-January 2024, 6.1% with inpatient/ED visits vs 12.0% with outpatient visits had received XBB.1.5 vaccination (aOR=0.41; 95% CI: 0.32-0.53). This protective association was weaker among JN.1 (aOR=0.62; 95% CI: 0.40-0.96) vs XBB-lineage (aOR=0.28; 95% CI: 0.18-0.43) variant infections (interaction, p=0.003). XBB.1.5 vaccination was also protective specifically compared to BA.4/BA.5-adapted mRNA vaccination (aOR=0.60; 95% CI: 0.45-0.79). XBB.1.5 vaccines protect against severe illness, but protection may be weaker against JN.1 vs XBB-lineage variants.

Proportion of Hospitalizations Preventable with Increased Oral SARS-CoV-2 Antiviral Treatment (preprint)

We estimated the proportion of hospitalizations that could have been averted had all eligible high-risk adults with SARS-CoV-2 infection in a clinical cohort been treated with an oral SARS-CoV-2 antiviral agent early in infection. Among 3,037 patients with risk factors for progressing to severe COVID-19, 946 (31.1%) received an oral antiviral prescription (834 nirmatrelvir and 112 molnupiravir). Only 3.0% of treated patients vs 9.1% of untreated patients were hospitalized (adjusted risk ratio [RR]=0.27; 95% confidence interval [CI]: 0.18-0.41). If all patients had been treated, an estimated 63.3% (95% CI: 50.4-75.1) of hospitalizations within 30 days could have been prevented. This finding is attributed to large gaps in treatment and a strong protective association of antiviral treatment with subsequent hospitalization.