Monitoring Incidence of COVID-19 Cases, Hospitalizations, and Deaths, by Vaccination Status — 13 U.S. Jurisdictions, April 4–July 17, 2021
Across 13 U.S. jurisdictions, age-standardized IRRs for cases in persons not fully vaccinated versus fully vaccinated decreased from 11.1 (95% CI = 7.8–15.8) during April 4–June 19 to 4.6 (95% CI = 2.5–8.5) during June 20–July 17, while IRRs decreased slightly from 13.3 (95% CI = 11.3–15.6) to 10.4 (95% CI = 8.1–13.3) for hospitalizations and from 16.6 (95% CI = 13.5–20.4) to 11.3 (95% CI = 9.1–13.9) for deaths during the same two periods. Case IRRs decreased, suggesting reduced vaccine effectiveness for prevention of SARS-CoV-2 infections. rates of COVID-19 cases, hospitalizations, and deaths were substantially higher in persons not fully vaccinated compared with those in fully vaccinated persons, similar to findings in other reports.
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
Among adults with ED/UC encounters for COVID-19–like illness (18,231; median patient age = 43 years, IQR = 29–62 years), laboratory-confirmed SARS-CoV-2 infections were identified among 28.9% (3,145 of 10,872) of unvaccinated and 7.0% (512 of 7,359) of fully vaccinated patients. VE against COVID-19 emergency departments and urgent care encounters was 82% (95% CI = 81%–84%). VE was highest among Moderna vaccine recipients (92%), followed by Pfizer-BioNTech vaccine recipients (77%), and was lowest (65%) for Janssen vaccine recipients. In this multistate interim analysis of 32,867 medical encounters among adults of all ages during June–August 2021, when the Delta variant was predominant in the United States, VE of all three authorized COVID-19 vaccines combined remained high against hospitalization (86%).
SARS-CoV-2 Transmission to Masked and Unmasked Close Contacts of University Students with COVID-19 — St. Louis, Missouri, January–May 2021
During January–May 2021, 265 students received a positive SARS-CoV-2 test result; these students named 378 close contacts. Compared with close contacts whose exposure only occurred when both persons were masked (7.7%), close contacts with any unmasked exposure (32.4%) had higher adjusted odds ratios (aORs) of receiving a positive SARS-CoV-2 test result (aOR = 4.9; 95% confidence interval [CI] = 1.4–31.1). Universal masking and fewer encounters in close proximity to persons with COVID-19 can limit the spread of SARS-CoV-2 in university settings.
Durability analysis of the highly effective BNT162b2 vaccine against COVID-19
[Preprint.] We conducted a test-negative case-control study to assess the durability of protection after full vaccination with BNT162b2 [Pfizer]. The primary population included 652 individuals who had a positive symptomatic test after full vaccination with BNT162b2 (cases) and 5,946 individuals with at least one negative symptomatic test after full vaccination (controls). The adjusted odds of symptomatic infection were higher 120 days after full vaccination versus at the date of full vaccination (Odds Ratio [OR]: 3.21, 95% confidence interval [CI]: 1.33-7.74). Importantly, the odds of infection were still lower 150 days after the first BNT162b2 dose as compared to 4 days after the first dose (OR: 0.3, 95% CI: 0.19-0.45), when immune protection approximates the unvaccinated status. Low rates of COVID-19 associated hospitalization or death in this cohort precluded analyses of these severe outcomes.
Metformin in Patients With COVID-19: A Systematic Review and Meta-Analysis
We identified 28 studies with 2,910,462 participants. Meta-analysis of 19 studies showed that metformin is associated with 34% lower COVID-19 mortality [odds ratio (OR), 0.66; 95% confidence interval (CI), 0.56–0.78; I2 = 67.9%] and 27% lower hospitalization rate (pooled OR, 0.73; 95% CI, 0.53–1.00; I2 = 16.8%). Our findings suggest a relative benefit for metformin use in nursing home and hospitalized COVID-19 patients. However, randomized controlled trials are warranted to confirm the association between metformin use and COVID-19 outcomes.