About

Clea Sarnquist is a Clinical Professor in Pediatrics with a focus on Infectious Diseases at Stanford University. Her work involves research and teaching in the field of infectious diseases, contributing to the academic and clinical understanding of pediatric infectious conditions. As part of the faculty at the Stanford Program in Human Biology, she is engaged in advancing knowledge in health sciences and educating students in related disciplines.

Research topics

• Medicine
• Political Science
• Environmental health
• Social psychology
• Medical education
• Public relations
• Applied psychology
• Psychiatry
• Psychology
• Internal medicine
• Clinical psychology
• Gastroenterology
• Immunology

Selected publications

• Symptoms, Viral Loads, and Rebound Among COVID-19 Outpatients Treated With Nirmatrelvir/Ritonavir Compared With Propensity Score–Matched Untreated Individuals

  UNC Libraries · 2025-03-18

  articleOpen access

  BACKGROUND: Nirmatrelvir/ritonavir (N/R) reduces severe outcomes from coronavirus disease 2019 (COVID-19); however, rebound after treatment has been reported. We compared symptom and viral dynamics in individuals with COVID-19 who completed N/R treatment and similar untreated individuals. METHODS: We identified symptomatic participants who tested severe acute respiratory syndrome coronavirus 2-positive and were N/R eligible from a COVID-19 household transmission study. Index cases from ambulatory settings and their households contacts were enrolled. We collected daily symptoms, medication use, and respiratory specimens for quantitative polymerase chain reaction for 10 days during March 2022-May 2023. Participants who completed N/R treatment (treated) were propensity score matched to untreated participants. We compared symptom rebound, viral load (VL) rebound, average daily symptoms, and average daily VL by treatment status measured after N/R treatment completion or 7 days after symptom onset if untreated. RESULTS: Treated (n = 130) and untreated participants (n = 241) had similar baseline characteristics. After treatment completion, treated participants had greater occurrence of symptom rebound (32% vs 20%; P = .009) and VL rebound (27% vs 7%; P < .001). Average daily symptoms were lower among treated participants without symptom rebound (1.0 vs 1.6; P < .01) but not statistically lower with symptom rebound (3.0 vs 3.4; P = .5). Treated participants had lower average daily VLs without VL rebound (0.9 vs 2.6; P < .01) but not statistically lower with VL rebound (4.8 vs 5.1; P = .7). CONCLUSIONS: Individuals who completed N/R treatment experienced fewer symptoms and lower VL but rebound occured more often compared with untreated individuals. Providers should prescribe N/R, when indicated, and communicate rebound risk to patients.

  PublisherDOI

• Associations of SARS-CoV-2 PCR positivity with clinical symptoms and race/ethnicity: The household transmission study

  PLoS ONE · 2025-09-30

  articleOpen accessCorresponding

  OBJECTIVE: The objective of this study was to identify demographic and clinical factors associated with SARS-CoV-2 infection among household contacts (HCs) following exposure to a confirmed case. METHODS: We analyzed an existing case-ascertained prospective cohort study of 43 HCs of SARS-CoV-2-positive index cases recruited from Stanford Health Care between March 2020 and June 2022. Participants self-collected nasal swabs daily for up to 21 days for reverse transcription polymerase chain reaction (RT-PCR) testing and reported symptoms in daily diaries. Using Cox proportional hazards models, we assessed associations between participant characteristics over time to first positive PCR result. RESULTS: We found that symptomatology and race/ethnicity were independently associated with increased infection risk. In multivariable analysis, participants with systemic symptoms had a higher likelihood of testing positive (adjusted hazard ratio [aHR]=2.62; 95% confidence interval [CI]: 1.38-6.55). Additionally, identifying as a racial/ethnic minority had a greater risk of a positive test (aHR = 2.55 for systemic symptoms, 2.43 for any respiratory symptoms, and 2.40 for upper respiratory symptoms) compared to white patients. CONCLUSION: These findings underscore the importance of symptom-based surveillance and highlight ongoing racial and ethnic disparities in SARS-CoV-2 transmission risk. This study also demonstrates the feasibility of longitudinal, self-administered testing and offers a scalable model for investigating transmission dynamics of respiratory viruses in community settings.

  PublisherDOI

• Social vulnerability and the risk of respiratory virus infection in households: a case-ascertained study

  Research Square · 2025-06-30

  preprintOpen access
  PublisherOA PDFDOI

• Social vulnerability and the risk of respiratory virus infection in households: a case-ascertained study

  BMC Infectious Diseases · 2025-12-13

  articleOpen access

  This study examines whether the Social Vulnerability Index (SVI), a location-based composite measure of social vulnerability, is associated with the risk of SARS-CoV-2 or influenza infection within households. Prospective cohort case-ascertained household transmission study. We analyzed data from a case-ascertained household transmission study conducted across multiple U.S. sites (September 2021–May 2023). Household contacts of index cases with confirmed infections self-collected nasal swabs daily for ten days, tested via RT-PCR for SARS-CoV-2 or influenza. Age, sex, and vaccine receipt were self-reported, with vaccination verified. Household addresses were geocoded to 2020 census tracts and linked to the national SVI percentile. Using modified Poisson regression models with generalized estimating equations, we assessed associations between census tract-level SVI and infection risk, adjusting for age, sex, vaccine receipt, and clustering by census tract. Participants included household contacts of index cases with SARS-CoV-2 (793 households, 1,408 participants) or influenza (273 households, 512 participants). We found that higher overall SVI was associated with increased SARS-CoV-2 infection risk (adjusted Incidence risk ratio [aIRR] 1.24; 95% CI: 1.00, 1.52). Specifically, the socioeconomic SVI domain was linked to higher infection risk (aIRR = 1.24; 95% CI: 1.02, 1.51). Other SVI domains were not statistically significant. For influenza, SVI was overall associated with greater infection, but confidence intervals crossed the null (aIRR = 1.45; 95% CI: 0.88, 2.39). Household contacts of SARS-CoV-2 index cases in high-SVI areas faced an increased risk of infection. No significant association was found for influenza, likely due to the small sample size. Increased access to SARS-CoV-2 testing, treatment, and preventive measures (e.g., masking, handwashing, isolation) may be especially important in high-SVI areas.

  PublisherDOI

• Acceptability and feasibility of implementing the Enhanced Assess, Acknowledge, Act (EAAA) sexual assault prevention intervention on a U.S. university campus: Themes from qualitative interviews and written reflections

  Journal of American College Health · 2024-05-16 · 2 citations

  articleSenior authorCorresponding

  EAAA translates well, with a few adaptations, to a residential campus environment in the U.S. Research is needed to assess program effectiveness in reducing sexual assault.

  PublisherDOI

• A Review of Evidence-Based Dating Violence Prevention Programs With Behavioral Change Outcomes for Adolescents and Young Adults

  Trauma Violence & Abuse · 2024-04-26 · 2 citations

  reviewSenior author

  Adolescent dating violence (DV) is not only a social but also a public health problem, necessitating the development and scale-up of prevention strategies. We conducted a review of the literature to identify adolescent and young adult DV prevention programs that have shown promising behavioral outcomes. The literature search covered articles published from 1996 to 2022 and indexed in Medline, Cochrane, Scopus, PsycINFO, and Embase. The review focused on programs implemented and evaluated in the United States or Canada that included intervention and comparison groups, a baseline assessment, and at least one post-assessment conducted after the intervention exposure. Promising behavioral outcomes were defined as positive, statistically significant differences between intervention and comparison groups with respect to DV perpetration or victimization or bystander behavior in relation to DV. A total of 118 articles were screened by abstract and read in-depth. Eighteen programs that met the inclusion criteria were identified. Of these programs, one showed reductions in DV victimization, six showed reductions in DV perpetration, and nine showed behavioral reductions in both violence perpetration and victimization. The review highlighted that while multiple programs have demonstrated efficacy in preventing or reducing intimate partner violence in North American youth populations, more robust research on the replication of these programs outside researcher-controlled environments is needed. Furthermore, issues with program inclusivity, such as with sex and gender-minority individuals, should be considered in future intervention development and replication research.

  PublisherDOI

• 925. Oseltamivir usage in community settings: data from a household transmission study

  Open Forum Infectious Diseases · 2023-11-27 · 2 citations

  articleOpen access

  Abstract Background Oseltamivir is the most common antiviral prescribed to treat influenza. There are limited data about oseltamivir receipt in uncomplicated influenza, including frequency of early discontinuation of oseltamivir. Methods Individuals who tested positive for influenza were identified from outpatient clinics, emergency departments, or surveillance testing at seven sites in the United States from December 2021–March 2023. Index cases and their household contacts (HHC) enrolled ≤6 days after the first illness in the household, completed symptom/medication logs, and collected nasal swabs for influenza testing daily for 10 days. Oseltamivir receipt was classified by daily logs (ever/never receipt, and duration of use: early discontinuation [1–2 days], 3–4 days, or ≥5 days) among eligible persons (Methods 1). Addresses linked to the 2020 Social Vulnerability Index by census tract. Odds of oseltamivir receipt were estimated using binomial regression with household clustering. Methods upload 1: Analytic flow diagram for assessment of use and discontinuation of oseltamivir in household settings, United States 2021-22 and 2022-23 influenza seasons. Discontinuation was defined as use for 1-2 days, compared to use for 3-4 or ≥5 days. If the participant reported oseltamivir on the first or last day of follow-up and did not report use for at least 3 days, the duration of oseltamivir usage was considered “censored” and discontinuation was not described. Results Of 737 household members, 142 individuals (90/235 index cases, 40/284 infected HHC, 12/218 uninfected HHC) reported oseltamivir. Oseltamivir receipt was more common among those recruited in 2022–23 vs. 2021–22 and by participants who self-reported pre-existing conditions vs. those who did not. Oseltamivir receipt was less common among children 5–11 vs. adults 18–49 years (Results 1). Individuals from the most vulnerable census tracts were least likely to receive oseltamivir (Results 2). Among symptomatic infected persons, oseltamivir was typically initiated within 2 days of symptoms (76%). Of 126 individuals whose duration of oseltamivir was not censored by the start or end of follow-up, 19% reported receipt on only 1-2 days, 17% for 3-4 days, and 63% for ≥5 days. Compared to those who reported ≥5 days of oseltamivir receipt, people who took oseltamivir for 1–2 days had similar reported symptoms, including gastrointestinal symptoms, on the first day of illness and first day of oseltamivir (Results 3). Results upload 1: Characteristics of individuals who did and did not report use of oseltamivir among individuals in households with a known influenza case, United States, 2021-22 and 2023-24 influenza seasons. Results Upload 2. Social vulnerability of individuals who did and did not report use of oseltamivir among individuals in geocoded households with a known influenza case, United States, 2021-22 and 2023-24 influenza seasons. Conclusion Over a third of index cases received oseltamivir, and receipt differed by age and social vulnerability status. In this analysis, early discontinuation was not associated with initial symptom burden or symptoms, including gastrointestinal side-effects, after initiating oseltamivir. Disclosures Edward Belongia, MD, Seqirus: Grant/Research Support Yvonne A. Maldonado, MD, Pfizer: Grant/Research Support|Pfizer: Site Investigator, DSMB member Suchitra Rao, MBBS, MSCS, Sequiris: Advisor/Consultant Huong McLean, PhD, MPH, Seqirus: Grant/Research Support Joshua Petrie, PhD, CSL Seqirus: Grant/Research Support Edwin J. Asturias, MD, Hillevax: Advisor/Consultant|Moderna: Advisor/Consultant|Pfizer: Grant/Research Support Carlos G. Grijalva, MD, MPH, AHRQ: Grant/Research Support|CDC: Grant/Research Support|FDA: Grant/Research Support|Merck: Advisor/Consultant|NIH: Grant/Research Support|Syneos Health: Grant/Research Support

  PublisherOA PDFDOI

• 2293. Examining social vulnerability and its effect on COVID-19 transmission in households

  Open Forum Infectious Diseases · 2023-11-27

  articleOpen access

  Abstract Background Social vulnerability impacts the transmission of SARS-CoV-2 (SCV2) among household contacts. Understanding these correlates can inform interventions to prevent infection among close contacts. We examined whether the social vulnerability index (SVI), a composite measure of socioeconomic status, household characteristics, racial and ethnic minority status, and housing type and transportation, is associated with the risk of SCV2 infection among household contacts. Overall Social Vulnerability Index Diagram Methods We used data from a multi-site, prospective, case-ascertained household transmission study with daily nasal swabs for 10 days and RT-PCR testing to detect SCV2 infections in household contacts. Age and gender were self-reported and vaccination status was self-reported and verified. We mapped households to 2020 census tracts and the 2020 SVI (Figure 1). We examined the association between census tract-level SVI (in quartiles) and the risk of infection among household contacts using Poisson regression with generalized estimating equations, accounting for household clustering. Inclusion criteria for analysis in this study. Inclusion criteria for analysis in this study. Results Among 1,171 household contacts from 719 households, 67.4% developed SCV2 infection. After adjusting for the age of the contact and study site, contacts living in the most vulnerable SVI quartiles, Q3 (Incidence Rate Ratio [IRR] 1.19, 95% CI 1.01-1.40) and Q4 (IRR=1.18, 95% CI 1.00-1.40), had higher rates of infection compared to those living in the least vulnerable quartile (Q1) at the census tract level. To describe the effect of SVI accounting for vaccination, we performed a second regression adjusting for vaccine receipt among participants. We found that Q3 (IRR 1.19, 95% CI 1.01-1.40) still had higher rates of infection compared to those living in the least vulnerable quartile (Q1). Q4 was directionally consistent but confidence bounds crossed 1 (IRR=1.17, 95% CI 0.99-1.39). Conclusion Household contacts from census tracts with greater social vulnerability at the census tract level had a greater risk of SCV2 infection. These risks held even after accounting for vaccine receipt among participants. Future public health interventions should focus on reducing infection and transmission among individuals living in areas with higher social vulnerability beyond vaccination coverage. Disclosures Carlos G. Grijalva, MD, MPH, AHRQ: Grant/Research Support|CDC: Grant/Research Support|FDA: Grant/Research Support|Merck: Advisor/Consultant|NIH: Grant/Research Support|Syneos Health: Grant/Research Support Suchitra Rao, MBBS, MSCS, Sequiris: Advisor/Consultant Edwin J. Asturias, MD, Hillevax: Advisor/Consultant|Moderna: Advisor/Consultant|Pfizer: Grant/Research Support Huong McLean, PhD, MPH, Seqirus: Grant/Research Support Edward Belongia, MD, Seqirus: Grant/Research Support Yvonne A. Maldonado, MD, Pfizer: Grant/Research Support|Pfizer: Site Investigator, DSMB member

  PublisherOA PDFDOI

• 930. COVID-19 symptom and viral load rebound among individuals reporting nirmatrelvir/ritonavir use compared to propensity score matched individuals not taking COVID-19 treatment

  Open Forum Infectious Diseases · 2023-11-27

  articleOpen access

  Abstract Background Nirmatrelvir/ritonavir (N/R) protects against severe outcomes after SARS-CoV-2 (SCV2) infection, but patients and studies have described symptom and viral rebound after treatment. Our aim was to compare symptom and viral trajectories during acute illness among individuals with COVID-19 treated with N/R compared to similar individuals who did not receive any COVID-19 treatment. Methods This analysis included participants enrolled ≤ 6 days of index symptom onset in a US household transmission study who tested SCV2-positive, Mar. 2022–Mar. 2023. We followed participants for 10 days after enrollment, obtaining demographics, clinical history, daily symptoms (list of 15), medications, and specimens for SCV2 quantitative PCR. Symptomatic participants eligible for N/R were included (Fig. 1). We used propensity score matching to select untreated participants who were similar to N/R treated participants (Table 1). We assessed symptoms and viral load (when ≥ 2 nasal swab results were available) from N/R completion (N/R treated) or after seven days since symptom onset (untreated) to the end of follow up. We defined symptom rebound as an increase of ≥ 2 symptoms and viral load rebound as an increase of ≥ 0.5 log10(IU/mL) over a minimum of 5 log10(IU/mL). We used Wilcoxon Test to compare mean daily symptoms and viral loads and logistic regression to calculate odds of rebound. Case-ascertained household transmission study participants were included in this analysis if they were enrolled in March 2022 (first report of nirmatrelvir/ritonavir) or after and tested positive for SARS-CoV-2 (n=2075). We included symptomatic N/R eligible participants who had non-missing data for propensity score model variables and daily specimens and symptoms (n=1224) and then excluded N/R treated participants who did not complete N/R in 5-6 days according to EUA (n=108). Propensity score matching was performed by calculating propensity score of nirmatrelvir/ritonavir use based on age, sex, race/ethnicity, prior COVID-19, recruitment method, participant type, medical care access, COVID-19 vaccination history, comorbidities, and predominant variant at the time of index onset. The best covariate balance was achieved using nearest propensity score matching method with a ratio of 2:1 no treatment to N/R treated. Those that did not match to a treated participant were excluded (n=768). The two recruitment sources collected different specimen types (sentinel sites collected nasal swabs and remote recruitment collected saliva) and used different viral load quantification standards. Because of this, viral load analysis was limited to only those that collected nasal swabs and had at least two viral load results after nirmatrelvir/ritonavir completion or, for the no treatment participants, after day 7 since symptom onset. N/R=nirmatrelvir/ritonavir; SCV2=SARS-CoV-2; EUA=Emergency Use Agreement Results N/R treated (n=116) and untreated (n=232) participants had similar baseline characteristics (Table 1). Median days from symptom onset to N/R initiation was 2 days (IQR=1-3). Symptom rebound occurred among 32% of N/R treated and 19% of untreated participants (OR=1.95; 95% CI=1.17, 3.24; Fig. 2). Mean daily symptoms were lower among N/R treated (1.6 vs 2.0; p=0.2) and significantly lower among N/R treated when rebound did not occur (0.8 vs 1.5; p=0.01). Viral load rebound occurred among 25% of N/R treated and 13% of untreated participants (OR=2.31; 95% CI=1.17, 4.55) and mean daily viral load was significantly lower among N/R treated overall (1.5 vs 2.7), without rebound (1.1 vs 2.5), and with rebound (4.8 vs 5.6, all p < 0.05, Fig. 3). The following symptoms were elicited daily from participants: fever/feverish/chills, cough, sore throat, runny nose, nasal congestion, fatigue/feeling run down, wheezing, trouble breathing/shortness of breath, chest tightness/chest pain, loss of smell/loss of taste, headache, abdominal pain, diarrhea, vomiting, and muscle or body aches. Symptom rebound was defined as an increase of at least two symptoms after the completion of nirmatrelvir/ritonavir or, when no treatment was reported, after seven days since symptom onset. Daily symptoms after end of treatment were averaged from the day after the last day of nirmatrelvir/ritonavir or, if no treatment, day eight since symptom onset to the last available symptom diary follow up. N/R=nirmatrelvir/ritonavirFigure 3.Viral load trajectory during the first two weeks after symptom onset by nirmatrelvir/ritonavir treatment and viral load rebound visualized by (A) median viral load each day since symptom onset and proportion with viral load rebound and (B) average daily viral load after nirmatrelvir/ritonavir completion or seven days since symptom onset Nasal swabs were tested for SARS-CoV-2 by PCR using the Panther Fusion Hologic system. Viral load as logIU/mL was determined using WHO standard. Negative results were set to zero and below limit of quantification (3 logIU/mL) results were set to 1.5 logIU/mL. Viral load rebound was defined as an increase of at least 0.5 logIU/mL (with a threshold of 5 logIU/mL) after the completion of nirmatrelvir/ritonavir or, if no treatment was reported, after seven days since symptom onset. Daily viral load after end of treatment was averaged from the day after the last day of nirmatrelvir/ritonavir or, if no treatment, day eight since symptom onset to the last available viral load result. N/R=nirmatrelvir/ritonavir; IU=international units Conclusion In outpatient settings, N/R treated individuals had fewer symptoms and lower viral loads, but greater odds of symptom and viral rebound compared to similar untreated individuals. Disclosures Joshua Petrie, PhD, CSL Seqirus: Grant/Research Support Suchitra Rao, MBBS, MSCS, Sequiris: Advisor/Consultant Edward Belongia, MD, Seqirus: Grant/Research Support Edwin J. Asturias, MD, Hillevax: Advisor/Consultant|Moderna: Advisor/Consultant|Pfizer: Grant/Research Support Huong McLean, PhD, MPH, Seqirus: Grant/Research Support Yvonne A. Maldonado, MD, Pfizer: Grant/Research Support|Pfizer: Site Investigator, DSMB member Carlos G. Grijalva, MD, MPH, AHRQ: Grant/Research Support|CDC: Grant/Research Support|FDA: Grant/Research Support|Merck: Advisor/Consultant|NIH: Grant/Research Support|Syneos Health: Grant/Research Support

  PublisherOA PDFDOI

• Mental health and gender-based violence: An exploration of depression, PTSD, and anxiety among adolescents in Kenyan informal settlements participating in an empowerment intervention

  PLoS ONE · 2023 · 23 citations

  Senior authorCorresponding
  • Medicine
  • Psychiatry
  • Clinical psychology

  OBJECTIVE: This study examines the prevalence of depression, anxiety, and post-traumatic stress disorder (PTSD) among adolescents attending schools in several informal settlements of Nairobi, Kenya. Primary aims were estimating prevalence of these mental health conditions, understanding their relationship to gender-based violence (GBV), and assessing changes in response to an empowerment intervention. METHODS: Mental health measures were added to the final data collection point of a two-year randomized controlled trial (RCT) evaluating an empowerment self-defense intervention. Statistical models evaluated how past sexual violence, access to money to pay for a needed hospital visit, alcohol use, and self-efficacy affect both mental health outcomes as well as how the intervention affected female students' mental health. FINDINGS: Population prevalence of mental health conditions for combined male and female adolescents was estimated as: PTSD 12.2% (95% confidence interval 10.5-15.4), depression 9.2% (95% confidence interval 6.6-10.1) and anxiety 17.6% (95% confidence interval 11.2% - 18.7%). Female students who reported rape before and during the study-period reported significantly higher incidence of all mental health outcomes than the study population. No significant differences in outcomes were found between female students in the intervention and standard-of-care (SOC) groups. Prior rape and low ability to pay for a needed hospital visit were associated with higher prevalence of mental health conditions. The female students whose log-PTSD scores were most lowered by the intervention (effects between -0.23 and -0.07) were characterized by high ability to pay for a hospital visit, low agreement with gender normative statements, larger homes, and lower academic self-efficacy. CONCLUSION: These data illustrate a need for research and interventions related to (1) mental health conditions among the young urban poor in low-income settings, and (2) sexual violence as a driver of poor mental health, leading to a myriad of negative long-term outcomes.

  PublisherDOI

Frequent coauthors

• Yvonne Maldonado

  99 shared

• Jeffrey Luther

  49 shared

• Mark Sawyer

  University of Tasmania

  49 shared

• Kris E. Calvin

  American Academy of Pediatrics

  49 shared

• Dean A. Blumberg

  University of California Davis Medical Center

  49 shared

• Wilbert H. Mason

  Kaiser Permanente Fontana Medical Center

  49 shared

• Jonathan Altamirano

  Stanford University

  19 shared

• Michael Baiocchi

  Stanford University

  16 shared