Assessing vaccine effectiveness against severe COVID-19 disease caused by omicron variant. Report from a meeting of the World Health Organization

Relative effectiveness of COVID-19 vaccination with 3 compared to 2 doses against SARS-CoV-2 B.1.1.529 (Omicron) among an Australian population with low prior rates of SARS-CoV-2 infection

“…Also ascertainment of severe disease using hospitalisations as a proxy may be biased if diagnosis of infection is incidental to the hospital admission rather than a contributory factor. [29] However, we were able to use ward admission types to assist in classifying hospitalisations related to Omicron, a method consistent with studies of severe disease conducted early in the pandemic [30] and showed that our method found a large proportion of individuals where the hospitalisation was likely due to COVID-19 (see Appendix 1 ). Finally ascertainment of infections changed during the course of this study.…”

Effectiveness of the neutralizing antibody sotrovimab among high-risk patients with mild-to-moderate SARS-CoV-2 in Qatar

“…With the lower severity of Omicron infections ( Butt et al, 2022 ), most COVID-19 hospitalizations during this time were with COVID-19, rather than because of COVID-19. Use of hospitalization as marker of COVID-19 severity can lead to bias in studies assessing effectiveness of interventions, particularly after Omicron emergence ( Feikin et al, 2022 , Stowe et al, 2022 ). Therefore, COVID-19 case severity was not assessed using records of hospitalization, but using specific criteria for case severity ( World Health Organization, 2021 ), criticality ( World Health Organization, 2021 ), and fatality ( World Health Organization, 2021 ) per WHO guidelines, a key strength of this study.…”

Clinical characteristics of the Omicron variant - results from a Nationwide Symptoms Survey in the Faroe Islands

“…The median time from the last vaccination was 177 days, and the continued protection of the vaccine can have faded to some degree during this time. In addition, our definition of severe disease is based on self-reported severity, as mentioned previously, and not hospitalization or ICU admission, as in many studies ( Feikin et al , 2022 ). Altarawneh et al found that previous infection alone, vaccination alone, and a combination of vaccination and previous infection all showed strong effectiveness against severe, critical, or fatal COVID-19 because of Omicron.…”