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. 2025 Jun 2;8(6):e2517402.
doi: 10.1001/jamanetworkopen.2025.17402.

Estimated 2023-2024 COVID-19 Vaccine Effectiveness in Adults

Ruth Link-Gelles  1   2 , Elizabeth A K Rowley  3 , Stephanie A Irving  4 , Nicola P Klein  5 , Shaun J Grannis  6   7 , Toan C Ong  8 , Sarah W Ball  3 , Malini B DeSilva  9 , Kristin Dascomb  10 , Allison L Naleway  4 , Padma Koppolu  4 , Ousseny Zerbo  5 , Bruce Fireman  5 , John Hansen  5 , Julius Timbol  5 , Lawrence Block  5 , Brian E Dixon  7   11 , Thomas J Duszynski  7   12 , Katie S Allen  7   11 , David Mayer  8 , Catia Chavez  8 , Michelle Barron  8 , Sarah E Reese  3 , Sean Chickery  3 , Jonathan M Davis  3 , Allison Avrich Ciesla  1   13 , Josephine Mak  1 , Morgan Najdowski  1   13 , Omobosola O Akinsete  9 , Charlene E McEvoy  9 , Inih J Essien  9 , Tamara Sheffield  10 , Daniel Bride  10 , Julie Arndorfer  10 , Joshua Van Otterloo  10 , Karthik Natarajan  14 , Mark W Tenforde  1 , Jennifer DeCuir  1   2 , Amanda B Payne  1
Affiliations

Estimated 2023-2024 COVID-19 Vaccine Effectiveness in Adults

Ruth Link-Gelles et al. JAMA Netw Open. .

Abstract

Importance: SARS-CoV-2 continues to evolve, population immunity changes, and COVID-19 vaccine formulas have been updated, necessitating ongoing COVID-19 vaccine effectiveness (VE) monitoring.

Objectives: To evaluate the VE of 2023-2024 COVID-19 vaccines against COVID-19-associated emergency department (ED) and urgent care (UC) encounters, hospitalizations, and critical illness, including during XBB- and JN.1-predominant periods.

Design, setting, and participants: This test-negative design VE case-control study was conducted using data from September 21, 2023, to August 22, 2024, from EDs, UC centers, and hospitals in 6 US health care systems. Eligible adults 18 years or older with COVID-19-like illness and molecular or antigen testing for SARS-CoV-2 were studied. Case patients were those with a positive molecular or antigen test result; control patients were those with a negative molecular test result.

Exposure: Receipt of 2023-2024 (monovalent XBB.1.5) COVID-19 vaccination with products approved or authorized for use in the US.

Main outcomes and measures: Main outcomes were COVID-19-associated ED and UC encounters, hospitalizations, and critical illness (admission to the intensive care unit or in-hospital death). VE was estimated comparing the odds of receipt of the 2023-2024 COVID-19 vaccine with no receipt among case and control patients.

Results: Among 345 639 eligible ED and UC encounters in immunocompetent adults 18 years or older with COVID-19-like illness and available test results (median [IQR] age, 53 [34-71] years; 209 087 [60%] female), 37 096 (11%) had a positive SARS-CoV-2 test result. VE against COVID-19-associated ED and UC encounters was 24% (95% CI, 21%-26%) during 7 to 299 days after vaccination. Among 111 931 eligible hospitalizations in immunocompetent adults 18 years or older with COVID-19-like illness and available test results (median [IQR] age, 71 [58-81] years), 10 380 (9%) had a positive SARS-CoV-2 test result. During 7 to 299 days after vaccination, VE was 29% (95% CI, 25%-33%) against COVID-19-associated hospitalization and 48% (95% CI, 40%-55%) against COVID-19-associated critical illness. VE was highest 7 to 59 days after vaccination (VE against ED and UC encounters 49%; 95% CI, 46%-52%; hospitalization, 51%; 95% CI, 46%-56%; critical illness, 68%; 95% CI, 56%-76%) and then waned (VE 180-299 days after vaccination against ED and UC encounters, -7% [95% CI, -13% to -2%]; hospitalization, -4% [95% CI, -14% to 5%]; and critical illness, 16% [95% CI, -6 to 34%]).

Conclusions and relevance: In this case-control study of VE, 2023-2024 COVID-19 vaccines were estimated to provide additional effectiveness against medically attended COVID-19, with the highest and most sustained estimates against critical illness. These results highlight the importance of receiving recommended COVID-19 vaccination for adults 18 years or older.

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Conflict of interest statement

Conflict of Interest Disclosures: Dr Klein reported receiving grants from Pfizer, Moderna, Merck, GlaxoSmithKline, Seqirus, AstraZeneca, and Janssen outside the submitted work. Dr Ball reported receiving funding from University of Utah outside the submitted work. Dr DeSilva reported receiving grants from Minnesota Department of Health outside the submitted work. Dr Naleway reported receiving grants from the National Institutes of Health outside the submitted work. Dr Zerbo reported receiving grants from Pfizer and Moderna outside the submitted work. Dr McEvoy reported receiving grants from GlaxoSmithKline, Astra-Zeneca, National Heart, Lung, and Blood Institute, and US Department of Defense outside the submitted work. No other disclosures were reported.

Figures

Figure 1.
Figure 1.. Vaccine Effectiveness (VE) by SARS-CoV-2 Variant Predominant Period Among Adults 18 Years or Older, September 2023 to August 2024
VE estimates were adjusted for age, race and ethnicity, sex, geographic region, calendar time. Error bars indicate 95% CIs. ED indicates emergency department; UC, urgent care. aVariant-specific periods were defined by time when more than 50% of sequenced specimens nationally belonged to the respective lineage: September 21 to December 23, 2023 (XBB predominance) and December 24, 2023, to August 22, 2024 (JN.1 predominance) bDue to the timing of the 2023-2024 COVID-19 vaccine recommendations and emergence of JN.1, VE during the XBB-predominant period could only be estimated to 98 days and 93 days past vaccination in the ED and UC as well as the hospital settings, respectively. To compare similar periods after dosing, we have included this abbreviated time period in the JN.1-predominant period estimates in addition to the full (ie, 7-299 day) period. cSome estimates are imprecise, which might be due to a relatively small number of persons in each level of vaccination or case status. This imprecision indicates that the actual VE could be substantially different from the point estimate shown, and estimates should therefore be interpreted with caution. Additional data accrual could increase precision and allow more precise interpretation.
Figure 2.
Figure 2.. Vaccine Effectiveness Among Adults 18 Years or Older Without Documented Immunocompromise, September 2023- August 2024
Vaccine effectiveness estimates were adjusted for age, race and ethnicity, sex, geographic region, calendar time. Error bars indicate 95% CIs. aVE indicates adjusted vaccine effectiveness; ED, emergency department; UC, urgent care. aSome estimates are imprecise, which might be due to a relatively small number of persons in each level of vaccination or case status. This imprecision indicates that the actual VE could be substantially different from the point estimate shown, and estimates should therefore be interpreted with caution. Additional data accrual could increase precision and allow more precise interpretation.
Figure 3.
Figure 3.. Relative 2- vs 1-Dose Vaccine Effectiveness (VE) Among Adults 65 Years or Older, April 2023 to August 2024
VE estimates were adjusted for age, race and ethnicity, sex, geographic region, calendar time. ED indicates emergency department; NA, not available; UC, urgent care.
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