About

Helen Y. Chu is a Professor in the Department of Epidemiology and also holds a position in Medicine - Allergy and Infectious Diseases at the University of Washington. She serves as the Program Lead for Infectious Disease at the Brotman Baty Institute and holds a Term Professorship in Medicine - Allergy and Infectious Diseases. Additionally, she is the Associate Dean for Research at the School of Public Health. Her research focuses on maternal immunization, particularly vaccines against influenza and respiratory syncytial virus (RSV). She studies the virologic and immunologic correlates of protection from respiratory viral infections in pregnant women, infants, and older adults. Her work includes performing clinical trials of vaccine candidates at domestic and international sites, such as Nepal and Bangladesh. She has developed immunologic assays to investigate transplacental transfer and decay kinetics of RSV antibodies, as well as genotypic analysis and molecular sequencing to study nosocomial and household transmission of respiratory viruses.

Research topics

• Medicine
• Virology
• Biology
• Internal medicine
• Computer Science
• Immunology
• Genetics
• Computational biology
• Nursing
• Pathology
• Telecommunications
• Econometrics
• Medical education
• Economics
• Psychiatry
• Statistics
• Mathematics
• Geography
• Demography
• Pediatrics
• Evolutionary biology

Selected publications

• Influenza household transmission and genomic diversity in the United States: A prospective cohort study, 2022–2024

  Journal of Infection · 2026-04-20

  articleOpen accessSenior author

  OBJECTIVES: To analyze the extent and risk factors of household influenza transmission using molecular testing and viral genomes. METHODS: In a community-based cohort in the United States during 2022-2024, participants self-collected weekly nasal swabs. Swabs were tested for influenza by RT-PCR; genomic sequencing was performed. Index cases had the first influenza detection within households. Factors associated with household transmission were evaluated using Poisson regression. RESULTS: Influenza transmission was detected in 56/303 influenza-positive households with a distinct index case. Most (82%) index cases were symptomatic; 16% of children vs 28% of adults were asymptomatic. 89/941 household contacts were infected 1-7 days after the index (secondary household infection risk: 9.5%, 95% CI: 7.3, 12.2). Index and secondary case median ages were 11 and 24 years, respectively. A greater proportion of contacts were infected when the index case was symptomatic (11%) vs asymptomatic (5%). Higher viral load was associated with 3.1 (1.7, 5.8) times higher risk of secondary infection. Most (13/16) index-secondary case pairs with available sequences differed by ≤3 nucleotides. CONCLUSIONS: Most household index cases were symptomatic children. Higher viral load and presence of symptoms among index cases were associated with household transmission. Home-based surveillance can assess household transmission using case chronology and genomics.

  PublisherDOI

• Re-infection with SARS-CoV-2 is associated with increased antibody breadth and potency against diverse sarbecovirus strains

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-10-06

  preprintOpen access

  ABSTRACT The ease with which emerging SARS-CoV-2 variants escape neutralizing antibodies limits protection afforded by a prior exposure, be it infection or vaccination. While rare, broadly neutralizing antibodies with activity towards diverse sarbecoviruses have been detected in convalescent serum. Motivated by findings that plasma responses show increased neutralization breadth and potency with continued antigen exposure, we isolated monoclonal antibodies (mAbs) after a SARS-CoV-2 re-infection and compared them to those isolated one year prior, after the first breakthrough infection. Among clonal lineage members identified at both time points, mAbs from the later time point showed improved neutralization potency and breadth. One mAb isolated after re-infection, C68.490, targets a conserved region in the receptor binding domain core and shows remarkable activity not only against SARS-CoV-2 variants, but also diverse sarbecoviruses from more distant clades present in animal reservoirs. These findings suggest that a focus on individuals with diverse and repeated antigen exposure could lead to identification of antibodies with therapeutic utility not just towards current and future SARS-CoV-2 variants, but also distant sarbecoviruses in the event of a future spillover.

  PublisherOA PDFDOI

• Knowledge About Respiratory Syncytial Virus and Acceptance of Infant Monoclonal Antibody for RSV and RSV Vaccination During Pregnancy

  The Pediatric Infectious Disease Journal · 2025-02-01 · 7 citations

  article

  BACKGROUND: Respiratory syncytial virus (RSV) is the leading cause of hospitalization among infants in the United States (US). RSV immunization, in the form of a monoclonal antibody (mAb) for infants and vaccines for pregnant people, may reduce infant RSV risk. METHODS: In April and May 2023, we surveyed adults with children in Oregon and Washington about the likelihood to accept infant mAb and maternal RSV vaccine and RSV awareness. We used multivariable logistic regression to identify predictors of self-reported likelihood of accepting RSV immunization. RESULTS: Among 1082 respondents, 68% and 70% responded they would very likely accept infant mAb or maternal RSV vaccine, respectively. Respondents had lower odds of accepting infant mAb (OR: 0.10, 95% CI: 0.07-0.15) and maternal RSV vaccine (OR: 0.16, 95% CI: 0.12-0.23) if they were somewhat or very concerned about side effects. Respondents had higher odds of accepting infant mAb if they received an influenza vaccination (OR: 3.79, 95% CI: 1.88-7.63). Respondents had higher odds of accepting maternal vaccine if they had an advanced degree (OR: 1.70, 95% CI: 1.06-2.73), had received an influenza vaccination (OR: 3.62, 95% CI: 1.80-7.25), or were aware of RSV before our survey (OR: 2.03, 95% CI: 1.03-4.01). CONCLUSION: Most respondents reported that they would likely accept RSV mAb for their infant or an RSV vaccine during pregnancy. Concerns about side effects lowered the odds of accepting immunization, however, nearly one-half of those concerned about side effects still expressed a high likelihood of accepting either immunization.

  PublisherDOI

• Scenario Projections of Respiratory Syncytial Virus Hospitalizations Averted Due to New Immunizations

  JAMA Network Open · 2025-06-11 · 5 citations

  articleOpen access

  Importance: In 2023, new immunization strategies became available for preventing respiratory syncytial virus (RSV) hospitalizations in infants and older adults. Modeling studies to understand the population-level impact of their use are important for public health planning. Objective: To estimate the number of hospitalizations averted in 2023 to 2024 due to new RSV immunization strategies and provide scenario projections for future seasons. Design, Setting, and Participants: This decision analytical model examined RSV hospitalizations in King County, Washington, from October 7, 2023, through April 26, 2025. The population of King County was disaggregated into infants younger than 6 months, infants aged 6 to 11 months, children aged 1 to 4 years, children/adults aged 5 to 59 years, adults aged 60 to 74 years, and adults aged 75 years or older. Exposures: Respiratory syncytial virus vaccination for adults aged 60 years or older, maternal RSV vaccination, and long-acting monoclonal antibodies (nirsevimab) for infants younger than 8 months. Main Outcomes and Measures: The proportion of RSV hospitalizations averted in adults aged 60 years or older and infants younger than 1 year were estimated using an RSV transmission model calibrated to RSV hospitalizations. Results: The RSV transmission model simulated the population of King County, which includes approximately 2.3 million individuals, with 23 700 infants younger than 1 year and 446 500 adults aged 60 years or older. During the 2023 to 2024 RSV season, 21.2% of adults aged 60 to 74 years, 32.7% of adults aged 75 years or older, and 33.0% of infants were protected through active or passive immunization. A total of 125 (95% projection interval [PI], 77-192) RSV hospitalizations were averted, with most of the benefit observed in infants younger than 6 months (28.6% [95% PI, 26.9%-30.5%] reduction from baseline) and adults aged 75 years or older (14.8% [95% PI, 14.3%-15.5%] reduction from baseline). For the 2024 to 2025 season, optimistic scenarios of high immunization coverage (50% in older adults and 80% in infants) projected reductions of 29.8% (95% PI, 29.1%-30.8%) in adults aged 75 years or older and 68.8% (95% PI, 66.0%-71.7%) in infants younger than 6 months compared with a counterfactual scenario with no immunizations. Targeting infants eligible for catch-up doses of nirsevimab early in the season increased the proportion of RSV hospitalizations averted in infants aged 6 to 11 months from 31.7% (95% PI, 29.4%-33.9%) to 40.4% (95% PI, 39.0%-42.1%). If vaccine protection in adults aged 75 years or older waned by 50% in the second year after immunization, the proportion of RSV hospitalizations averted was projected to decrease to 22.2% (95% PI, 21.7%-23.0%). Conclusions and Relevance: In this decision analytical model of RSV immunizations, the results suggest a modest reduction in RSV-diagnosed hospitalizations during the 2023 to 2024 season due to limited availability of immunization products, particularly for infants. A higher uptake earlier in the season may lead to substantial reductions in RSV hospitalizations in the 2024 to 2025 season.

  PublisherOA PDFDOI

• The Path Forward for Vaccine Policy in the United States

  New England Journal of Medicine · 2025-07-30 · 5 citations

  article1st authorCorresponding
  PublisherDOI

• Correlates of risk of respiratory syncytial virus disease: a prospective cohort study

  Nature Communications · 2025-09-26 · 4 citations

  articleOpen accessSenior author

  Few population-based studies have evaluated the importance of pre-existing respiratory syncytial virus (RSV) antibody on RSV susceptibility among children and adults. We conducted a prospective, community-based cohort study among individuals aged 6 months-50 years in Oregon and Washington State, USA (June 2022-May 2023), with weekly symptom surveys and swab collection regardless of symptoms. Swabs were tested for RSV using RT-qPCR. Enrollment sera were tested for RSV prefusion F IgG binding (all participants) and neutralizing antibodies (pediatric participants). We detected 305 RSV illnesses among 3237 participants from 1188 households. Using proportional hazards regression, higher RSV binding antibody titers were associated with a lower estimated hazard of RSV among pediatric participants (hazard ratio=0.66 per 1-unit difference in log10-RSV antibody titer; 95% CI: 0.56, 0.78). In a post-pandemic period, pre-existing RSV antibody titers were associated with a lower risk of RSV illness in children aged 6 months-17 years, which could inform vaccine development for this age group. This study found higher RSV antibody levels were associated with lower RSV risk in children outside the hospital. An earlier rise in incidence and higher incidence rates were observed among children <5 years compared to older children and adults.

  PublisherOA PDFDOI

• Shot Through the Heart—Can RSV Vaccination Reduce Risk of Cardiovascular Outcomes?

  JAMA · 2025-08-30 · 2 citations

  article1st authorCorresponding
  PublisherDOI

• Infant CD4 T-Cell Response to SARS-CoV-2 mRNA Vaccination Is Restricted in Cytokine Production and Modified by Vaccine Manufacturer

  Open Forum Infectious Diseases · 2025-09-25 · 1 citations

  articleOpen access

  Background: Safe and effective vaccines are a key preventative measure to protect infants from SARS-CoV-2 infection and disease. Although mRNA vaccines induce robust antibody titers in infants, little is known about the quality of CD4 T-cell responses induced by vaccination. CD4 T-cell responses are important in orchestrating coordinated immune responses during infection and may help to limit disease severity. Methods: To characterize the CD4 T-cell response to SARS-CoV-2 mRNA vaccination in infants, we sampled blood from 13 infants before and after primary SARS-CoV-2 mRNA vaccine series; samples from 12 historical vaccinated adults were used for comparisons. Peripheral blood mononuclear cells were stimulated with spike peptide pools, and the ability of CD4 T-cells to secrete Th1, Th2, and Th17 cytokines was quantified. Measures of polyfunctionality were generated with the COMPASS algorithm. Results: = .08). This contrasted with adults, in whom vaccination induced robust production of IFN-γ, IL-2, and TNF-α. Th2 and Th17 responses were limited in both infants and adults. In infants, CD4 T-cell responses post vaccination were greater in those who received mRNA-1273 vs BNT162b. In contrast to CD4 T-cell responses, spike-specific IgG titers were similar in infants and adults. Conclusions: These data suggest that infants have restricted induction of cytokine-producing CD4 T-cells following SARS-CoV-2 mRNA vaccination relative to adults.

  PublisherOA PDFDOI

• A promise fulfilled: Updates on respiratory syncytial virus vaccines and monoclonal antibodies

  Journal of Allergy and Clinical Immunology · 2025-11-04 · 4 citations

  reviewSenior author
  PublisherDOI

• Investigating Symptom Duration Using Current Status Data: A Case Study of Postacute COVID-19 Syndrome.

  UNC Libraries · 2025-06-12

  articleOpen access

  BACKGROUND: For infectious diseases, characterizing symptom duration is of clinical and public health importance. Symptom duration may be assessed by surveying infected individuals and querying symptom status at the time of survey response. For example, in a severe acute respiratory syndrome coronavirus 2 testing program at the University of Washington, participants were surveyed at least 28 days after testing positive and asked to report current symptom status. This study design yielded current status data: outcome measurements for each respondent consisted only of the time of survey response and a binary indicator of whether symptoms had resolved by that time. Such study design benefits from limited risk of recall bias, but analyzing the resulting data necessitates tailored statistical tools. METHODS: We review methods for current status data and describe a novel application of modern nonparametric techniques to this setting. The proposed approach is valid under weaker assumptions compared with existing methods, allows the use of flexible machine learning tools, and handles potential survey nonresponse. Our method relies on the assumption that the survey response time is conditionally independent of symptom resolution time within strata of measured covariates, and we propose an approach to assess the sensitivity of results to deviations from conditional independence. RESULTS: From the university study, we estimate that 19% of participants experienced ongoing symptoms 30 days after testing positive, decreasing to 7% at 90 days. We found the estimates to be more sensitive to violations of the conditional independence assumption at 30 days compared with 90 days. Female sex, fatigue during acute infection, and higher viral load were associated with slower symptom resolution. CONCLUSION: The proposed method and accompanying sensitivity analysis procedure provide tools for investigators faced with current status data.

  PublisherDOI

Recent grants

• Prospective Community-Based Study of RSV Risk Factors in Nepalese Children

  NIH · $897k · 2013–2018

Frequent coauthors

• Janet A. Englund

  295 shared

• Trevor Bedford

  Fred Hutch Cancer Center

  248 shared

• Lea M. Starita

  208 shared

• Jay Shendure

  Howard Hughes Medical Institute

  192 shared

• Peter D. Han

  134 shared

• Deborah A. Nickerson

  University of Washington

  130 shared

• Caitlin R. Wolf

  University of Washington

  99 shared

• Michael Boeckh

  Fred Hutch Cancer Center

  97 shared

Labs

• Helen Y. Chu LaboratoryPI

Awards & honors

• Term Professorship, Medicine - Allergy and Infectious Dis.