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 Quadrivalent human papillomavirus (HPV) Vaccine Evaluation Study with Addition of the Nonavalent Vaccine Study (QUEST-ADVANCE) aims to provide insight into the long-term immunogenicity and effectiveness of one, two and three HPV vaccine doses. Here, we describe the protocol for QUEST-ADVANCE.

QUEST-ADVANCE is an observational cohort study including males and females who are unvaccinated or vaccinated with the quadrivalent or nonavalent HPV vaccine in British Columbia, Canada. Female participants who are unvaccinated or vaccinated with 1–3 doses of the quadrivalent or nonavalent HPV vaccine at 9–14 years of age will be recruited approximately 5 or 12 years postvaccination eligibility. Male participants who are unvaccinated or vaccinated with 1 or 2 doses of the nonavalent HPV vaccine at 9–14 years of age will be recruited at approximately 5 years postvaccination eligibility. The study involves a maximum of four visits over a period of 4–5 years for female participants, and two visits over a 12-month period for male participants. At each visit, self-collected swabs (cervico-vaginal or penile) and questionnaire data will be collected. In each study group, a subset of participants will be invited to participate in a substudy evaluating the long-term humoral immunogenicity of the HPV vaccine. Additional blood samples will be collected from participants who are part of the immunogenicity substudy. The total required sample size is 7180 individuals. The primary objectives are (1) to examine vaccine effectiveness in males and females against prevalent genital HPV infections for one, two and three doses of the HPV vaccine compared with unvaccinated participants and (2) to evaluate if there is non-inferior immunogenicity as indicated by type-specific antibody response of one dose of the HPV vaccine in 20–27-year-old females vaccinated at 9–14 years of age compared with historical data of three doses of the HPV vaccine females vaccinated at 16–26 years of age up to 12 years postvaccination.

QUEST-ADVANCE was approved by the Research Ethics Board of the University of British Columbia/Children’s and Women’s Health Centre of British Columbia (H20-02111). Individual electronic informed consent or assent will be obtained from each participant before any study-specific procedures are undertaken. Results will be published in an international peer-reviewed journal and on the study website.