Fourth COVID vaccine dose tied to 78% lower risk of death in older Israelis
Israelis aged 60 and older given a fourth dose of the Pfizer/BioNTech COVID-19 vaccine amid the Omicron surge had a 64% lower risk of hospitalization and 78% lower risk of death than those who received three doses, suggests an observational study published yesterday in Nature Medicine.
Clalit Health Services researchers compared the outcomes of 328,597 patients who received a fourth COVID-19 vaccine dose with those of 234,868 patients who received three doses. Israelis 60 and older who had received a third dose at least 4 months before became eligible for a fourth dose on Jan 3, 2022, and study follow-up began 1 week later. Average patient age was 73.0 years, and 53% were women.
In the fourth-dose group, 270 patients were hospitalized, compared with 550 in the three-dose group (hazard ratio [HR], 0.36; 95% confidence interval [CI], 0.31 to 0.43). Ninety-two fourth-dose patients died, as did 232 third-dose recipients (adjusted HR, 0.22; 95% CI, 0.17 to 0.28).
Risk factors for death included age 70 to 79 (HR, 2.24) and 80 to 100 (HR, 9.95), male sex (HR, 1.59), chronic heart failure (HR, 4.11), chronic obstructive pulmonary disease (COPD) (HR, 1.82), diabetes (HR, 2.06), and stroke (HR, 1.84).
Risk factors for hospitalization included age 70 to 79 (HR, 1.82) and 80 to 100 (HR, 4.04), male sex (HR, 1.53), chronic heart failure (HR, 2.17), chronic kidney failure (HR, 2.27), COPD (HR, 2.24), diabetes (HR, 1.43), high blood pressure (HR, 1.39), ischemic heart disease (HR, 1.21), and stroke (HR, 1.43).
"Although this study is observational in nature, we believe that its substantial findings and the observed potential for avoiding the most severe COVID-19 outcomes could assist decision-makers in assessing the benefit of providing the second-booster to targeted populations," the researchers wrote. "Studies with long-term follow-up to determine the durability of the second-booster effectiveness against severe disease and safety are warranted."
Apr 25 Nat Med study
When hospitalized, Omicron patients require similar care to Delta patients
Though they need hospital care much less often, patients hospitalized with the Omicron SARS-CoV-2 variant require similar levels of respiratory support and intensive care unit (ICU) treatment as those with the Delta variant, according to a Johns Hopkins study published in the May issue of eBioMedicine.
The study involved 1,119 Omicron and 908 Delta patients diagnosed from Nov 22 to Dec 31, 2021, in the Washington, DC, area. The researchers found that the Omicron patients were 67% less likely to require hospitalization, 62% less likely to need ICU care, and 74% less likely to die than their Delta-infected counterparts.
Once in the hospital, however, patients with Omicron had a similar need for supplemental oxygen and ICU care as hospitalized Delta patients. Among Omicron patients, 67.6% required supplemental oxygen, and 17.6% were taken to an ICU. For Delta, 73% needed supplemental oxygen, and 25.4% required ICU-level care.
The researchers found no significant differences in viral loads between the two groups, regardless of vaccination status.
"It's true that patients with omicron were significantly less likely to be admitted to the hospital than patients with delta," said senior author Heba Mostafa, MBBCh, PhD, in a Johns Hopkins news release. "But omicron patients who did need hospitalization faced a risk of severe disease comparable to those hospitalized with delta. For many people, it is not a mild infection at all."
May EBioMedicine study
Apr 25 Johns Hopkins news release