About

Kristen A. Feemster, M.D., M.P.H., M.S.H.P.R., is an Adjunct Associate Professor of Pediatrics (Infectious Diseases) at the Perelman School of Medicine at the University of Pennsylvania. She is also a Senior Fellow at the Leonard Davis Institute of Health Economics and holds faculty positions at the Center for Pediatric Clinical Effectiveness, the Global Health Program, and PolicyLab at the Children's Hospital of Philadelphia. Dr. Feemster directs research at the Vaccine Education Center at the Children's Hospital of Philadelphia and is involved in clinical and research activities related to infectious diseases, pediatrics, and vaccine policy. Her educational background includes a BS in Biology from Yale University, an MPH in Population and Family Health from Columbia University Mailman School of Public Health, an MD from Columbia University College of Physicians and Surgeons, and an MSHRP in Health Policy Research from the University of Pennsylvania School of Medicine. Her research expertise encompasses health services research, infectious diseases epidemiology, vaccine policy, vaccine-preventable diseases, immunizations, and GIS methodology. Dr. Feemster's work focuses on improving vaccine education, policy, and practice, contributing to the fields of pediatric infectious diseases and health economics.

Research topics

• Internal medicine
• Biology
• Microbiology
• Medicine
• Immunology
• Genetics
• Virology
• Pediatrics

Selected publications

• P-1478. Trends in Streptococcus pneumoniae serotypes and antimicrobial resistance among US adults ≥18 years old with invasive and noninvasive pneumococcal disease (2022-2023)

  Open Forum Infectious Diseases · 2026-01-01

  articleOpen accessSenior author

  Abstract Background Antimicrobial resistance (AMR) is a global public threat. Pneumococcal conjugate vaccines (PCVs) contribute both directly and indirectly to combating AMR. The US Advisory Committee on Immunization Practices (ACIP) recommends PCV21 for adults ≥50 years (yrs). PCV21 provides serotype (ST) coverage for 83% of invasive pneumococcal disease (IPD) with 30% of cases caused by eight STs not included in other licensed vaccines. It is important to monitor S. pneumoniae epidemiology and AMR trends to understand the impact of new PCVs. We evaluated ST distribution and antimicrobial susceptibility of S. pneumoniae obtained from adult patients (≥18 yrs) with invasive pneumococcal disease (IPD) and non-IPD during 2022-2023. Methods : S. pneumoniae isolates causing IPD and non-IPD were collected from 30 sites in 19 states between 2022 and 2023. Whole genome sequencing of the S. pneumoniae isolates was performed using Illumina NextSeq sequencers (Illumina, San Diego, CA, USA). Capsular locus sequences were extracted and analyzed using the PneumoCaT database for serotype determination. Antimicrobial susceptibility tests were performed using the broth microdilution method. Results Among the 675 S. pneumoniae isolates, ST3 was the most common (12.3%), followed by 35B (9.8%), 9N (6.8%), 22F (6.4%), 11A (6.1%), 19F (6.1%), 23A (5.6%), and 15A (5.2%), with PCV21 covering 83% of isolates compared to 50% for PCV20. PCV20 STs demonstrated susceptibility to penicillin (80.7%), ceftriaxone (99.4%), and azithromycin (63.5%). In contrast, PCV21 STs demonstrated lower susceptibility to penicillin (65.3%), ceftriaxone (98.8%), and azithromycin (53.7%). PCV21 unique STs demonstrated the lowest susceptibility to penicillin (52%), azithromycin (49.5%), and doxycycline (77.8%) compared to other vaccine types. Serotypes, 35B (3%), 23A (52.6%), and 23B (52.6%) demonstrated the lowest penicillin susceptibility. Conclusion Newly introduced PCVs include several serotypes associated with high rates of AMR, particularly PCV21 whose unique serotypes had the lowest penicillin susceptibility. Thus, new PCVs have the potential to help reduce AMR. However, continued surveillance is needed to evaluate trends in the impact of PCVs on ST epidemiology and AMR over time. Disclosures Mekki Bensaci, PhD, Merck: Employee Karri A. A. Bauer, PharmD, Merck: Employee Kenneth Klinker, PharmD, Merck: Employee Jason Cota, PharmD, Merck: Employee Pavel Prusakov, PharmD, Merck: Employee Rodrigo E. Mendes, PhD, GSK: Grant/Research Support|Shionogi & Co., Ltd.: Grant/Research Support|United States Food and Drug Administration: FDA Contract Number: 75F40123C00140 Kristen Feemster, MD, Merck: Employee

  PublisherOA PDFDOI

• Health disparities in the burden of pneumococcal disease in US adults

  Pneumonia · 2026-04-07

  articleOpen accessSenior author

  There are significant racial and environmental disparities in the burden of pneumococcal disease. Understanding the role of social determinants of health (SDoH) on pneumococcal disease can help health authorities identify health inequities and develop interventions to reduce these disparities. This targeted literature review (TLR) aimed to examine the clinical and economic burden of pneumococcal disease in US adults with a focus on SDoH such as race, urbanicity, and socioeconomic status. A TLR of studies published between January 2012 and July 2024 was conducted using PubMed (via Medline) and Centers for Disease Control and Prevention (CDC) surveillance data. Supplementary searches were made on Google Scholar to address data gaps. Outcomes of interest were incidence, prevalence, mortality, healthcare resource use, costs, and vaccine coverage rates by race/ethnicity, urbanicity (population density), and socioeconomic variables (income, education, employment status and home ownership). Of 4,609 identified publications, 12 studies were included. Black adults had the highest incidence and mortality rates and longest hospital stay due to pneumococcal disease across all adult age groups. Additionally, Black (compared to non-Black) adults were more likely to be hospitalized at younger ages (50–64 years). Black adults ≥50 years incurred significantly higher pneumococcal disease hospitalization costs compared to non-Black adults. Lower urbanicity displayed higher mortality rates for adults with pneumonia. Adult patients 18–64 years living in more disadvantaged areas had a higher risk of hospitalization for IPD. Similarly, adults living in higher levels of area-based poverty had increased rates of CAP hospitalizations. Incidence of community-acquired pneumonia (CAP) was higher in early retirees and their adult dependents compared to their employed counterparts and adult dependents. Vaccination rates were lower in Black adults, rural residents, those with lower SES, education or income, blue-collar workers, and those who did not own a home. Disparities in pneumococcal disease burden and vaccination uptake exist among US adults, particularly among Black adults, rural residents and those with lower education and income. There is paucity of studies examining disparities in pneumococcal disease and inequities according to race, urbanicity, and socioeconomic status warranting further investigation of the topic to inform prevention strategies.

  PublisherOA PDFDOI

• Alterations of the Upper Respiratory Microbiome Among Children Living With HIV Infection in Botswana

  The Journal of Infectious Diseases · 2025-08-12

  articleOpen access

  Children living with HIV (CLWH) are at high risk of colonization and infection by respiratory pathogens, though this risk can be reduced by other microbes in the upper respiratory microbiome. The impact of HIV infection on the pediatric upper respiratory microbiome is poorly understood, and we sought to address this knowledge gap by identifying associations between HIV infection and the nasopharyngeal microbiomes of Batswana children. We enrolled Batswana CLWH (<5 years) and age- and sex-matched HIV-exposed, uninfected and HIV-unexposed, uninfected children in a cross-sectional study. We used shotgun metagenomic sequencing to compare nasopharyngeal microbiomes by HIV status. Among the 143 children in this study, HIV and HIV-associated immunosuppression were associated with alterations in nasopharyngeal microbiome composition, including lower abundances of Corynebacterium species associated with resistance to bacterial pathogen colonization. These findings suggest that the upper respiratory microbiome may contribute to the high risk of respiratory infections among CLWH.

  PublisherOA PDFDOI

• Health state utilities associated with invasive pneumococcal disease, pneumonia, and recurrent acute otitis media in young children

  Quality of Life Research · 2025-01-03 · 4 citations

  articleOpen access

  PURPOSE: Cost-utility analyses examining the value of new vaccines for pneumococcal disease will require health state utilities as inputs. Existing utilities for pneumococcal infections in young children are limited. The purpose of this study was to estimate health state utilities associated with pneumococcal infections in young children. METHODS: Six health state vignettes depicting infections due to Streptococcus pneumoniae were drafted based on published literature and clinician interviews. To address methodological challenges in estimating utilities for temporary infections in children 0-5 years of age, several time trade-off approaches were explored in a pilot study (N = 28 participants). In the subsequent utility elicitation study conducted in the UK, health states were valued using the best performing method from the pilot (10-year time horizon, with infections repeated annually) with adult general population respondents imagining a child 2-5 years of age. RESULTS: A total of 208 participants completed interviews (51.9% female; mean [SD] age = 41.0 [14.9] years). Mean (SD) utilities were 0.902 (0.092) for pneumonia requiring hospitalization, 0.901 (0.087) for bacteremia, 0.894 (0.103) for recurrent acute otitis media (AOM), 0.882 (0.107) for recurrent AOM treated with pressure equalization tubes, 0.878 (0.109) for bacteremic pneumonia, and 0.809 (0.145) for meningitis. CONCLUSION: Lower health state utilities were associated with health states that had longer treatment periods, required more invasive treatment, and described more severe infections. Utilities from this study can be used in models examining cost-effectiveness of pneumococcal vaccines. These results have methodological implications for future research estimating utilities associated with temporary pediatric health conditions.

  PublisherOA PDFDOI

• Influence of area-level social vulnerability on all-cause pneumonia incidence among adult Medicare and Medicaid enrollees

  Communications Medicine · 2025-11-14 · 1 citations

  articleOpen accessSenior author

  BACKGROUND: The incidence of pneumonia varies by demographic and clinical factors, but less is known about the influence of area-level social determinants of health. METHODS: Using Medicare and Medicaid claims, we characterized the relationship between the county-level Minority Health Social Vulnerability Index (MHSVI) and all-cause pneumonia (ACP), pneumococcal pneumonia (PP) and invasive pneumococcal disease (IPD) incidence from 2016 to 2019. RESULTS: We show that in Medicare ( ≥ 65 years, 55% female) and Medicaid (ages 19-64, 58% female), ACP incidence is 8052 and 1819 per 100,000 person-years, respectively. Across both cohorts, rates are highest among enrollees who are male, non-Hispanic white, older, at high risk for pneumococcal disease (those with immunocompromising or other serious conditions such as cancer), and rural county residents. Among high-risk Medicare and Medicaid enrollees, ACP incidence is higher in the most versus least socially vulnerable counties, whereas the opposite is observed among moderate-risk enrollees (those with chronic conditions such as diabetes) and low-risk enrollees (those without chronic or immunocompromising conditions). CONCLUSIONS: Controlling for individual characteristics attenuated the relationship between vulnerability and disease incidence overall and in most subgroups. Within MHSVI themes, ACP incidence is higher for the most versus least vulnerable counties based on Medical Vulnerability and Household Composition and Disability themes versus the overall MHSVI. Results for secondary outcomes (PP and IPD) follows similar patterns as for ACP but are weaker in magnitude and significance.

  PublisherOA PDFDOI

• 8 months to 5 days: what happened when Pennsylvania changed the vaccination regulations for provisional enrollment?

  UNC Libraries · 2025-07-18

  articleOpen access

  In March 2017, the Pennsylvania Department of Health reduced the time allowed to demonstrate compliance with school-entry vaccination requirements from eight months to five days. We describe changes in provisional enrollment, vaccine exemptions, and vaccine coverage rates before and after the new regulation. Across Pennsylvania, provisional enrollment decreased from 11.1% in 2016/17 to 2.5% in 2017/18 (77% relative decrease). Personal belief exemptions continued a modest upward trend, similar to previous years, and medical exemptions remained steady. Among kindergartners, coverage with &ge; 2 doses of MMR vaccine and 2 doses of Varicella vaccine increased; similar increases were seen for the MCV and Tdap vaccines among 7th graders. However, improvements in coverage and reductions in provisional enrollment were not consistent across counties. Provisional enrollment in Philadelphia County during the 2017/18 school year (10.4%) did not substantially decrease. The statewide reduction in provisional enrollment suggests that the new regulations accomplished the goal of increasing the proportion of students who are up-to-date on required vaccines at the beginning of the school year without a significant increase in vaccine exemptions. However, the persistence of high provisional enrollment in some counties points to additional barriers to this goal in some schools and regions.

  PublisherDOI

• P-242. Disparities and inequities in the burden of pneumococcal disease in US adults

  Open Forum Infectious Diseases · 2025-01-29

  articleOpen access

  Abstract Background Understanding the impact of social determinants of health on pneumococcal disease (PD) is important. The purpose of this study was to conduct a targeted literature review (TLR) of the clinical and economic burden of PD in US adults with a focus on examining disparities and inequities by race, geography, urbanicity, income, education, and employment. Methods Original research studies reporting burden of PD in US adults published between 2012 and January 2024 were identified through a US focused TLR in Pubmed (vial Medline) and a review of surveillance data from the CDC website. The original search was supplemented with targeted searches via Google Scholar in areas for which data were not identified via Pubmed or the CDC website. Results Of 4,133 identified publications, 16 studies were identified: 10 described disparities by race, 7 by geography, 2 by urbanicity, 3 by income, 1 by education and 1 by employment. Black adults had the highest incidence and longest length of stay due to IPD and bacteremic community acquired pneumonia (CAP) and highest mortality rates from CAP compared to other racial groups across all adult age groups; Black adults living in poverty experienced a 2.1 times higher rate of PD compared to white adults. Pneumococcal disease also varied by geography and urbanicity. Lower urbanicity displayed higher mortality rates for PD. Incidence of all-cause CAP was higher in early retirees 18–64 years old and their adult dependents compared to their employed counterparts and their adult dependents. PD health care expenditures mirror the patterns observed for disease burden. Vaccination rates were lower in Black adults compared to white adults and in adults who resided in rural areas, were less educated and had a lower income. Conclusion This TLR confirms that disparities and inequities in the burden of PD among US adults exist with higher disease burden and lower pneumococcal vaccination in Black adults, those living in rural areas and with lower education and income. There is a paucity of studies examining inequities and social disparities of health in PD. Additional studies are needed to examine disparities and inequities in PD according to race, geography, urbanicity, income, education, and employment. Disclosures Salini Mohanty, DrPH, MPH, Merck &amp; Co., Inc.: Employee|Merck &amp; Co., Inc.: Stocks/Bonds (Public Company) Kelly D. Johnson, PhD, Merck &amp; Co., Inc.: Employee|Merck &amp; Co., Inc.: Stocks/Bonds (Public Company) Sheba Nellore, MBA, Merck: Advisor/Consultant Lindsay McNamee, BSc, Merck &amp; Co Inc.: Advisor/Consultant Hanane Khoury, PhD, Merck: Advisor/Consultant Laura De Benedetti, BSc, Merck &amp; Co, Inc: Advisor/Consultant Elmira Flem, MD, PhD, Merck: Stocks/Bonds (Private Company) Kristen A. Feemster, MD, MPH, MSHPR, FAAP, Merck &amp; Co., Inc., Rahway, NJ, USA: Grant/Research Support|Merck &amp; Co., Inc., Rahway, NJ, USA: Stocks/Bonds (Public Company) Nicole Cossrow, PhD, Merck: Stocks/Bonds (Public Company)

  PublisherDOI

• Additional file 1 of Influence of area-level social vulnerability on all-cause pneumonia, all-cause acute otitis media, and invasive pneumococcal disease incidence among Medicaid-enrolled children

  Open MIND · 2025-01-01

  article

  supplementary material 1

  DOI

• Corrigendum to “Changes in pneumococcal vaccination disparities by area-level social vulnerability during the COVID-19 pandemic among Medicare and Medicaid enrollees” [Vaccine 62 (2025) 127452]

  Vaccine · 2025-10-18

  erratumSenior author
  PublisherDOI

• Changes in pneumococcal vaccination disparities by area-level social vulnerability during the COVID-19 pandemic among Medicare and Medicaid enrollees

  Vaccine · 2025-07-15 · 2 citations

  articleOpen accessSenior author

  BACKGROUND: The COVID-19 pandemic amplified long-standing health disparities in the United States and spurred new research into factors associated with vaccine uptake. While much of the focus has been on COVID-19 vaccines, few studies have examined disparities in pneumococcal vaccination. METHODS: Using a retrospective cohort design, we assessed how disparities in county-level pneumococcal vaccination rates by social vulnerability level changed across two periods: before COVID-19 (Medicare: 2016-2019; Medicaid: 2017-2019) and during COVID-19 (2020-2022). Vaccination data were derived from the claims of adult Medicare enrollees (aged ≥65 years) and Medicaid enrollees (aged 19-64), whereas social vulnerability was measured using the Minority Health Social Vulnerability Index. We analyzed changes in vaccine uptake disparities using a difference-in-differences regression model adjusted for demographics and clinical factors. FINDINGS: Both before and during COVID-19, vaccination rates were lower among enrollees residing in high-vulnerability counties. During the pandemic, disparities in pneumococcal vaccination rates decreased among the 37.5 million Medicare enrollees analyzed but increased among the 8.1 million Medicaid enrollees. These patterns remained even after adjusting for enrollee demographic and clinical characteristics. INTERPRETATION: During COVID-19, Medicare enrollees exhibited reduced disparities in pneumococcal vaccination, possibly due to heightened risk perception, whereas Medicaid enrollees experienced widening gaps, likely driven by socioeconomic barriers. These findings highlight the complex interplay of individual demographic and clinical characteristics, and area-level social vulnerability in shaping vaccine uptake. To improve public health, initiatives should consider these multifaceted factors to effectively address disparities.

  PublisherDOI

Recent grants

• NIH Grant K08HS020939

  NIH · $676k · 2017

Frequent coauthors

• Andrew P. Steenhoff

  Children's Hospital of Philadelphia

  92 shared

• Susan Coffin

  Children's Hospital of Philadelphia

  66 shared

• Tonya Arscott‐Mills

  University of Pennsylvania

  63 shared

• Matthew S. Kelly

  Duke University

  55 shared

• Samir S. Shah

  Community Eye Care Foundation

  47 shared

• Alexander G. Fiks

  Children's Hospital of Philadelphia

  45 shared

• Paul A. Offit

  Children's Hospital of Philadelphia

  29 shared

• Robert W. Grundmeier

  Children's Hospital of Philadelphia

  29 shared