Interim Estimates of COVID-19 Vaccine Effectiveness Against COVID-19–Associated Emergency Department or Urgent Care Clinic Encounters and Hospitalizations Among Adults During SARS-CoV-2 B.1.617.2 (Delta) Variant Predominance — Nine States, June–August 2021

Abstract

this report was posted as an MMWR Early Release on the MMWR website (https://www.cdc.gov/mmwr).Data on COVID-19 vaccine effectiveness (VE) since the B.1.617.2 (Delta) variant of SARS-CoV-2, the virus that causes COVID-19, became the predominant circulating strain in the United States are limited (1-3). CDC used the VISION Network* to examine medical encounters (32,867) from 187 hospitals and 221 emergency departments (EDs) and urgent care (UC) clinics across nine states during June-August 2021, beginning on the date the Delta variant accounted for >50% of sequenced isolates in each medical facility's state. VISION Network methods have been published (4).Eligible medical encounters were defined as those among adults aged ≥18 years who had received SARS-CoV-2 molecular testing (primarily reverse transcription-polymerase chain reaction assay within 14 days before or 72 hours after the admission or encounter) and a COVID-19-like illness discharge diagnosis. Vaccination status was documented in electronic health records and immunization registries. Full vaccination was defined as receipt of the second dose of BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) mRNA vaccines, or a single dose of Ad26.COV2 (Janssen [Johnson & Johnson]) vaccine ≥14-days before the testing or encounter date. Patients who had received no COVID-19 vaccine doses were considered unvaccinated. Patients who had received 1 mRNA dose only or had received the second dose <14 days before testing or encounter date were excluded. VE was estimated using a test-negative design, calculating the odds of receiving a positive SARS-CoV-2 test result comparing fully vaccinated and unvaccinated patients (referent group). VE was adjusted for age, geographic region, calendar time (days from January 1 to medical event), and virus circulation, and weighted for inverse propensity to be vaccinated or unvaccinated (calculated separately for each VE model). VE estimates with 95% confidence intervals (CIs) that did not overlap were considered statistically different. This activity

Effectiveness of 2-Dose Vaccination with mRNA COVID-19 Vaccines Against COVID-19–Associated Hospitalizations Among Immunocompromised Adults — Nine States, January–September 2021

“…To evaluate vaccine effectiveness (VE) among immunocompromised adults, data from the VISION Network* on hospitalizations among persons aged ≥18 years with COVID-19-like illness from 187 hospitals in nine states during January 17-September 5, 2021 were analyzed. Using selected discharge diagnoses, † VE against COVID-19-associated hospitalization conferred by completing a 2-dose series of an mRNA COVID-19 vaccine ≥14 days before the index hospitalization date § (i.e., being fully vaccinated) was evaluated using a test-negative design comparing 20,101 immunocompromised adults (10,564 * Funded by CDC, the VISION Network includes Columbia University Irving Medical Center, New York, New York; HealthPartners Minnesota and Wisconsin; Intermountain Healthcare, Salt Lake City, Utah; Kaiser Permanente Northern California, Oakland, California; Kaiser Permanente Northwest, Portland, Oregon; Regenstrief Institute, Indianapolis, Indiana; and University of Colorado, Aurora, Colorado. † Immunocompromised status was defined as the presence of at least one discharge diagnosis, using diagnosis codes from International Classification of Diseases, Ninth Revision (ICD-9) and International Classification of Diseases, Tenth Revision (ICD-10), for solid malignancy (ICD-10 codes: C00-C80, C7A, C7B, D3A, Z51.0, and Z51.1), hematologic malignancy (ICD-10 codes: C81-C86, C88, C90-C96, D46, D61.0, D70.0, D61.2, D61.9, and D71), rheumatologic or inflammatory disorder (ICD-10 codes: D86, E85 [except E85.0], G35, J67.9, L40.54, L40.59, L93.0, L93.2, L94, M05-M08, M30, M31.3, M31.5, M32-M34, M35.3, M35.8, M35.9, M46, and T78.40), other intrinsic immune condition or immunodeficiency (ICD-10 codes: D27.9, D61.09, D72.89, D80, D81 [except D81.3], D82-D84, D89 [except D89.2], K70.3, K70.4, K72, K74.3-K74.6 [except K74.60 and K74.69], N04, and R18), or organ or stem cell transplant (ICD-10 codes: T86 [except T86.82-T86.84, T86.89, and T86.9], D47.Z1, Z48.2, Z94, and Z98.85).…”

“…Among immunocompromised patients, VE was also calculated separately among subgroups of patients with each of the five categories of immunocompromising diagnoses (subgroups that were not mutually exclusive). VE was also calculated separately for hospitalizations occurring before and after the period when the Delta variant accounted for ≥50% of sequenced isolates within each site's state (10). VE estimates with 95% CIs that did not overlap were considered statistically different, which is a conservative approach.This study was reviewed and approved by Westat, Inc. institutional review board.…”

Laboratory-Confirmed COVID-19 Among Adults Hospitalized with COVID-19–Like Illness with Infection-Induced or mRNA Vaccine-Induced SARS-CoV-2 Immunity — Nine States, January–September 2021

“…For the next secondary § Index test date was defined as the date of respiratory specimen collection associated with the most recent positive or negative SARS-CoV-2 test result before the hospitalization or the hospitalization date if testing only occurred after admission. ¶ https://www.cdc.gov/coronavirus/2019-ncov/php/invest-criteria.html analysis, aORs for hospitalizations that occurred before and during SARS-CoV-2 B.1.617.2 (Delta) variant predominance (June-September 2021) were compared, beginning on the date the Delta variant accounted for >50% of sequenced isolates in each medical facility's state (2). Finally, effect modification was assessed by mRNA vaccine product or by age group; p-values <0.2 were considered indicative of a statistically significant difference in aOR by product or age, similar to previous modeling studies of effect modification (4).…”

Effectiveness of the mRNA-1273 Vaccine during a SARS-CoV-2 Delta Outbreak in a Prison

“… To the Editor: The mRNA vaccines have been shown to be highly effective in preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and associated illness, 1 , 2 although recent reports suggest reduced effectiveness against infection with the B.1.617.2 (or delta) variant. 3 , 4 We assessed the effectiveness of the mRNA-1273 (Moderna) vaccine among incarcerated men during a coronavirus disease 2019 (Covid-19) outbreak that was dominated by transmission of the delta variant.…”