TABLE. COVID-19 vaccine effectiveness* against laboratory-confirmed COVID-19–associated emergency department and urgent care clinic encounters and hospitalizations^† among adults during SARS-CoV-2 B.1.617.2 (Delta) variant predominance,^§ by outcome, age group, and vaccine — nine states,^¶ June–August 2021.

Outcome	Total	No. of SARS-CoV-2–positive tests (row %)	VE, % (95% CI)
All adults (aged ≥18 yrs), any COVID-19 vaccine
COVID-19 hospitalizations
Unvaccinated (ref)	6,960	1,316 (18.9)	—
Fully vaccinated**	7,676	235 (3.1)	86 (82–89)
COVID-19 ED/UC encounters
Unvaccinated (ref)	10,872	3,145 (28.9)	—
Fully vaccinated**	7,359	512 (7.0)	82 (81–84)
COVID-19 hospitalizations, any COVID-19 vaccine, by age
Age group = 18–74 yrs
Unvaccinated (ref)	5,708	1,185 (20.8)	—
Fully vaccinated**	4,551	134 (2.9)	89 (85–92)
Age group = ≥75 yrs
Unvaccinated (ref)	1,252	131 (10.5)	—
Fully vaccinated**	3,125	101 (3.2)	76 (64–84)
COVID-19 hospitalizations by COVID-19 vaccine
BNT162b2 (Pfizer-BioNTech)
Unvaccinated (ref)	6,960	1,316 (18.9)	—
Fully vaccinated**	4,243	135 (3.2)	80 (73–85)
mRNA-1273 (Moderna)
Unvaccinated (ref)	6,960	1,316 (18.9)	—
Fully vaccinated**	2,975	70 (2.4)	95 (92–97)
Ad26.COV2.S (Janssen)
Unvaccinated (ref)	6,960	1,316 (18.9)	—
Fully vaccinated**	458	30 (6.5)	60 (31–77)
COVID-19 ED/UC encounters by COVID-19 vaccine
BNT162b2 (Pfizer-BioNTech)
Unvaccinated (ref)	10,872	3,145 (28.9)	—
Fully vaccinated**	3,946	314 (8.0)	77 (74–80)
mRNA-1273 (Moderna)
Unvaccinated (ref)	10,872	3,145 (28.9)	—
Fully vaccinated**	2,656	98 (3.7)	92 (89–93)
Ad26.COV2.S (Janssen)
Unvaccinated (ref)	10,872	3,145 (28.9)	—
Fully vaccinated**	757	100 (13.2)	65 (56–72)

Abbreviations: CI = confidence interval; ED = emergency department; HHS = U.S. Department of Health and Human Services; Janssen = Johnson & Johnson vaccine; Ref = referent group; UC = urgent care; VE = vaccine effectiveness.

* VE was estimated using a test-negative design, adjusted for age, geographic region, calendar time (cubic spline with quartile knots), and virus circulation (percentage of SARS-CoV-2–positive results from testing within the counties surrounding the facility on the date of the event) and weighted for inverse propensity to be vaccinated or unvaccinated (calculated separately for each of the 10 VE models) using facility characteristics, sociodemographics, and underlying medical conditions.

^† Medical events with a discharge code consistent with COVID-19-like illness were included, such as acute respiratory illness (e.g., COVID-19, respiratory failure, or pneumonia) or related signs or symptoms (cough, fever, dyspnea, vomiting, or diarrhea) using diagnosis codes from the ninth and tenth revisions of the International Classification of Diseases. Clinician-ordered molecular assays (e.g., real-time reverse transcription–polymerase chain reaction) for SARS-CoV-2 occurring ≤14 days before to <72 hours after hospital admission or ED/UC encounter were included.

^§ Medical events occurred when Delta variant was predominant (>50%) in each state, according to data from network partners, CDC COVID data tracker (https://covid.cdc.gov), and HHS Protects Public Data Hub (https://protect-public.hhs.gov).

^¶ Partners contributing both ED/UC encounters and hospitalizations in 2021 were in Indiana (range of earliest to latest medical event: July 3–26), Oregon and Washington (June 30–August 4), and Utah (June 1–July 24). Partners contributing hospitalizations only were in California (June 23–August 4), Colorado (June 3–July 20), Minnesota and Wisconsin (July 1–August 2), and New York (June 30–July 25).

** Full vaccination was defined as index testing or admission date ≥14 days after second dose of BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) or after a single dose of Ad26.COV2 (Janssen) vaccines.