Clinical Report: Trends in Neutralizing Antibody Levels Against Enterovirus D68

Overview

This longitudinal study assessed the prevalence and 48-week dynamics of neutralizing antibodies against enterovirus D68 (EV-D68) among adult retail workers during the COVID-19 pandemic. Seropositivity exceeded 85% at both visits. Although overall antibody titers declined significantly, most participants had less than a 4-fold change between visits.

Background

EV-D68 causes acute respiratory illness and can lead to acute flaccid myelitis. Infections have been reported mainly among children, although adults—particularly those with underlying conditions—are also affected. Neutralizing antibodies provide functional evidence of virus-specific immunity, but their precise protective role in human EV-D68 infection remains unclear. Adult antibody dynamics have been poorly characterized.

Data Highlights

Key Findings

• Overall geometric mean titer declined significantly from 69 to 59 during follow-up.

• Significant declines occurred among women and participants aged 40–59 years.

• Significant within-group declines were also observed among participants with obesity or diabetes, those reporting fewer than 10 gatherings, and those with positive SARS-CoV-2 serology.

• Six participants had an increase of at least 4-fold, consistent with possible recent EV-D68 or other enterovirus exposure.

• Eight participants had a decrease of at least 4-fold, with geometric mean titer declining from 129 to 13.

• Testing used a 2014 clade B1 strain and may not have captured the full breadth of responses to more recently circulating EV-D68 subclades.

Clinical Implications

High seropositivity was consistent with substantial previous EV-D68 exposure among adults in this cohort. The overall decline in antibody titers may reflect natural waning, although most participants remained within a 4-fold range. Marked increases in a small subgroup raise the possibility of EV-D68 or another enterovirus circulating in Quebec after nonpharmaceutical interventions were relaxed. These findings require cautious interpretation because cross-neutralization may occur and the study tested only one historical EV-D68 strain.

Conclusion

EV-D68 neutralizing antibodies were detected in more than 85% of participants. Titers declined overall during 48 weeks of follow-up, but 93% of participants had less than a 4-fold change. Studies using contemporary strains in similar adult cohorts are needed to characterize cross-subclade immunity and support adult EV-D68 serologic surveillance.

Related Resources & Content

1. Dynamics of Neutralizing Antibodies Against Enterovirus D68 in Adults During the COVID-19 Pandemic — Rahajamanana VL, Rabezanahary H, Arroyave A, et al. International Journal of Infectious Diseases. 2026;171:109008. doi:10.1016/j.ijid.2026.109008.

2. Clinical Presentation of Enterovirus D68 in Adults With Acute Respiratory Infections Consulting in Emergency Departments in Quebec, Canada — Mallet MC, Trottier S, Baz M, et al. IJID Regions. 2025;15:100669.

3. Global Age-Stratified Seroprevalence of Enterovirus D68: A Systematic Literature Review — Jorgensen D, Grassly NC, Pons-Salort M. The Lancet Microbe. 2025;6(1):100938.

4. Multimodal Surveillance Model for Enterovirus D68 Respiratory Disease and Acute Flaccid Myelitis Among Children in Colorado, USA, 2022 — Messacar K, Matzinger S, Berg K, et al. Emerging Infectious Diseases. 2024;30:423–431.