Fig. 2: Relative risk of attendance, admission or death, BA.2 versus BA.1 by age group.

Risk of hospitalisation and mortality, overall and by age group, for COVID-19 cases with Omicron lineage BA.2 compared to BA.1 in England, 01 December 2021–2025 March 2022. The central measures are adjusted hazard ratios and the errors bars are the corresponding 95% confidence intervals from Cox regression models stratified for exact specimen date, area of residence, age group and vaccination status, and additionally using regression adjustments for within-age-group residual differences in exact age, sex, ethnicity, index of multiple deprivation (IMD) quintile and within-IMD-quintile residual differences in exact IMD rank, and reinfection status. A shows risk of any hospital attendance, including admissions, within 14 days of the earliest specimen date in the COVID-19 episode following infection with SARS-CoV-2 lineage BA.2, compared to BA.1. B shows the risk of hospital admission within 14 days. C shows the risk of death within 28 days. For the death outcome, hazard ratios were not estimated for cases aged <20 years due to small numbers. Likelihood ratio test (LRT) P values from two-sided tests for interaction between age group and variant status for attendance, admission, and death are 0.010, 0.0003958, and 0.003 respectively. These explorative tests were not adjusted for multiple comparisons. The adjusted hazard ratio estimates and 95% confidence intervals that the figure is based on are included in Table S3.