July 16, 2021

Study describes characteristics of hospitalised COVID-19 patients who were fully-vaccinated

Findings from a study published in Clinical Microbiology and Infection showed that severe coronavirus disease 2019 (COVID-19), associated with a high mortality rate, might develop in a minority of fully-vaccinated individuals with multiple comorbidities. 

“mRNA COVID-19 vaccines have shown high effectiveness in the prevention of symptomatic COVID-19, hospitalisation, severe disease, and death. Nevertheless, a minority of vaccinated individuals might get infected and suffer significant morbidity,” wrote Tal Brosh-Nissimov, Samson Assuta Ashdod University Hospital, Ashdod, Israel, and colleagues. “Characteristics of vaccine breakthrough infections have not been studied. We sought to portray the population of Israeli patients, who were hospitalised with COVID-19 despite full vaccination.”

A total of 152 patients who received the BNT162b2 (Pfizer-BioNTech) COVID-19 vaccine and developed COVID-19, requiring hospitalisation, more than 7 days after receiving the second vaccine dose were included in the retrospective multicentre cohort study.

The primary outcome was a composite of mechanical ventilation or in-hospital death, referred to as poor outcome, whereas favourable outcome was defined as patients who were either discharged or were still hospitalised but not ventilated at the end of the study.

The median time elapsed from the second-dose vaccination to admission was 39.5 days (range 8-97), and the majority (82%) of patients were admitted 21 days or more after vaccination, which, noted the researchers, supported the assumption that the patients were not infected before vaccination. The median age was 71.1 (range 22-98) and most (70%) were males. 

The cohort was characterised by a high prevalence of comorbidities including hypertension (71%), diabetes (48%), congestive heart failure (CHF; 27%), chronic kidney diseases (24%) and chronic lung diseases (24%), dementia (19%), and cancer (24%), with only 6 (4%) patients having no comorbidities. Additionally, immunosuppression was present in 60 (40%) patients. Common causes of immunosuppression were chronic corticosteroid treatment, chemotherapy or anti-metabolite treatment, solid organ transplantation and anti-CD20 treatment.

Overall, the primary outcome of mechanical ventilation or death occurred in 38 patients (25%), with a mortality rate of 22% (34/152). Among the 114 patients who had a favourable outcome, 12 were still hospitalised but not ventilated at the end of the study period. A comparison of baseline risk-factors between the groups did not identify any statistically-significant differences. Some nonsignificant differences of-note included a higher prevalence of anti-CD20 treatment (13% vs 4%, P = 0.12), cancer (32% vs 22%, P = 0.23), CHF (34% vs 25%, P = 0.25) and dementia (26% vs 17%, P = 0.19) among patients with a poor outcome compared with those who had a favourable outcome. 

“This representative cohort of hospitalised patients is characterised by older age, high rate of comorbidities predisposing for progression to severe COVID-19, and a high rate of immunosuppression. The outcome of these patients was similar to that of non-vaccinated hospitalised COVID-19 patients,” the authors noted. 

“Additional prospective longitudinal studies are urgently needed to identify predictors for vaccine breakthrough infection and simple correlates of vaccine protection, to enable identification of individuals at higher risk, who would require continued strict precautions, and possibly repeated active vaccination or other prophylactic measures, such as passive vaccination,” the authors added.

SOURCE: Clinical Microbiology and Infection