The Omicron variant of SARS-CoV-2 has emerged as the predominant strain of COVID-19 since 2022. Its association with prior vaccines remained under investigation.

Retrospective cohort study.

Clinical data for patients, from 1 May 2022 to 31 January 2023, were extracted from the Chi-Mei Medical Center, Chiali electronic medical record databases.

Hospitalised COVID-19 patients in dedicated wards were enrolled in the study. Cases of COVID-19 reinfection and relapse were also included. Patients who did not have COVID-19, those with PCR repositivity, or those with incomplete laboratory data were excluded.

Various doses of vaccines included primary series, additional dose and booster. The types of vaccines included ChAdOx1-S, mRNA-based vaccines and recombinant protein vaccine. The interval between the last vaccination date and the diagnosis date of COVID-19 was assessed.

The primary outcome was all-cause mortality by day 30. The secondary outcomes were severe disease of COVID-19 and 90-day survival.

Among 469 cases, the adjusted HR for 30-day mortality in vaccinated compared with unvaccinated patients was 0.831 (95% CI 0.541 to 1.277; p=0.398), indicating no statistically significant association. Age, Charlson Comorbidity Index (CCI), quick Sequential Organ Failure Assessment score and administration of dexamethasone were recognised as powerful predictors for survival in multivariable analysis. In subgroup analysis, a statistically significant association with better 30-day survival was observed among patients aged

Vaccination was associated with lower mortality in younger or low-CCI patients, but not in older or highly comorbid patients.

The burden of rheumatoid arthritis (RA) is profound, although treated with the treat-to-target strategy for RA patients according to the two most influential organisations for rheumatology worldwide. The need to timely achieve the control of disease activity for RA patients, especially for those difficult-to-treat individuals, is still unmet. Besides, the data on the diagnosis and prognosis of RA-related complications or comorbidities such as sarcopenia, cardiovascular diseases (CVD), malignancies and infections in large real-world cohorts are still limited. Therefore, the aim of this large-scale cohort study is to identify the development of clinical, biomedical, histopathological and imaging biomarkers for the diagnosis and prognosis of difficult-to-treat RA, and RA-related complications/comorbidities and to evaluate their impact on the prognosis of RA.

In this real-world multicentre prospective cohort, consecutive RA patients are planned to be recruited during 2024 and 2033 and with at least 5-year follow-up. Sociodemographic characteristics collection, clinical assessment, muscle assessment, histopathological assessment, imaging examination and biological samples collection will be performed at baseline, 1st, 3rd, 6th and 12th month during the first year and subsequently every 6 months until 5 years to repeat the assessments and collect the information of interested outcomes. The outcomes of interest include RA disease outcomes (including disease activity, functional and radiographic indicators) and RA-related complications/comorbidities (eg, sarcopenia, CVD, malignancies and specific infection).

Ethical approval has been approved by the Medical Ethics Committee of Sun Yat-sen Memorial Hospital, Sun Yat-sen University (ID: SYSKY-2023-1235-01); the Affiliated Panyu Central Hospital of Guangzhou Medical University (ID: PYRC-2024-214-01); and ShenShan Medical center, Memorial Hospital of Sun Yat-sen University (ID: 2024-SSKY-118-01). All study participants sign an informed consent form. Dissemination of results will occur via national and international conferences, in peer-reviewed journals, public conferences and social media.

NCT06233929.