Hospitalized patients with severe COVID-19 during the Omicron wave in Israel - benefits of a fourth vaccine dose.

BACKGROUND: Waning vaccine-immunity and an increased incidence of COVID-19 during the Omicron outbreak led the Israeli Ministry of Health to recommend a fourth dose of BNT162b2 for high-risk individuals. This study assessed the effect of that dose for hospitalized patients with severe/critical, breakthrough COVID-19. METHODS: In this multi-center retrospective cohort study of hospitalized adults with severe/critical COVID-19 in Israel, from 01/15/2022-01/31/2022, cases were divided according to the number of vaccinations received. Poor outcome was defined as mechanical ventilation or in-hospital death, and was compared between 3- and 4-dose vaccinees using logistic regression. RESULTS: Included were 1,049 patients, median age 80 years (IQR 69-87), 51% males. Among them, 394 were unvaccinated, 386 had received 3 doses and 88 4 doses. The 3-dose group was older, had more males and immunosuppression, but with similar outcomes, 49% vs. 51% compared to unvaccinated patients (p = 0.72). Patients after 4 doses were similarly older and immunosuppressed, but had better outcomes compared to unvaccinated patients, 34% vs. 51% (p < 0.01). We examined independent predictors for poor outcome in patients with either 3 or 4 doses, received a median of 161 (IQR 147-168) or 14 (IQR 10-18) days before diagnosis, respectively. Receipt of the fourth dose was associated with protection: OR 0.51 (95%CI 0.3-0.87), as was Remdesivir OR 0.65 (95%CI 0.44-0.96). Male sex, chronic renal failure and dementia were associated with poor outcomes. CONCLUSIONS: Among hospitalized patients with severe/critical breakthrough COVID-19, a recent fourth dose was associated with significant protection against mechanical ventilation or death, compared to three doses.

Hospitalised patients with breakthrough COVID-19 following vaccination during two distinct waves in Israel, January to August 2021: a multicentre comparative cohort study.

BackgroundChanging patterns of vaccine breakthrough can clarify vaccine effectiveness.AimTo compare breakthrough infections during a SARS-CoV-2 Delta wave vs unvaccinated inpatients, and an earlier Alpha wave.MethodsIn an observational multicentre cohort study in Israel, hospitalised COVID-19 patients were divided into three cohorts: breakthrough infections in Comirnaty-vaccinated patients (VD; Jun-Aug 2021) and unvaccinated cases during the Delta wave (ND) and breakthrough infections during an earlier Alpha wave (VA; Jan-Apr 2021). Primary outcome was death or ventilation.ResultsWe included 343 VD, 162 ND and 172 VA patients. VD were more likely older (OR: 1.06; 95% CI: 1.05-1.08), men (OR: 1.6; 95% CI: 1.0-2.5) and immunosuppressed (OR: 2.5; 95% CI: 1.1-5.5) vs ND. Median time between second vaccine dose and admission was 179 days (IQR: 166-187) in VD vs 41 days (IQR: 28-57.5) in VA. VD patients were less likely to be men (OR: 0.6; 95% CI: 0.4-0.9), immunosuppressed (OR: 0.3; 95% CI: 0.2-0.5) or have congestive heart failure (OR: 0.6; 95% CI: 0.3-0.9) vs VA. The outcome was similar between all cohorts and affected by age and immunosuppression and not by vaccination, variant or time from vaccination.ConclusionsVaccination was protective during the Delta variant wave, as suggested by older age and greater immunosuppression in vaccinated breakthrough vs unvaccinated inpatients. Nevertheless, compared with an earlier post-vaccination period, breakthrough infections 6 months post-vaccination occurred in healthier patients. Thus, waning immunity increased vulnerability during the Delta wave, which suggests boosters as a countermeasure.