Covid-19 Sentry

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From Preprints

  1. Participants: 1,035,163 people aged 18-100 years who tested positive for SARS-CoV-2 in the national surveillance programme, and had an infection identified as either Omicron- or Delta compatible. Main outcome measures: Death involving COVID-19 as identified from death certification records. The exposure of interest was the SARS-CoV-2 variant identified from NHS Test and Trace PCR positive tests taken in the community (pillar 2) and analysed by Lighthouse laboratories. Cause-specific Cox proportional hazard regression models were adjusted for sex, age, vaccination status, previous infection, calendar time, ethnicity, Index of Multiple Deprivation rank, household deprivation, university degree, keyworker status, country of birth, main language, region, disability, and comorbidities. Additionally, we tested for interactions between variant and sex, age, vaccination status and comorbidities. Results: The risk of death involving COVID-19 was 67% lower for Omicron compared to Delta and the reduction in the risk of death involving COVID-19 for Omicron compared to Delta was more pronounced in males than in females and in people under 70 years old than in people aged 70 years or over. Regardless of age, reduction of the risk of death from Omicron relative to Delta more was more pronounced in people who had received a booster than in those having received only two doses. Conclusions: Our results support early work showing the relative reduction in severity of Omicron compared to Delta in terms of hospitalisation and extends this research to assess COVID-19 mortality. Our work also highlights the importance of the vaccination booster campaign, where the reduction in risk of death involving COVID-19 is most pronounced in individuals who had received a booster.

    🖺 Full Text HTML: Risk of COVID-19 related deaths for SARS-CoV-2 Omicron (B.1.1.529) compared with Delta (B.1.617.2)
  1. METHODS: Two national matched, retrospective cohort studies were conducted to estimate effectiveness of BA.1 infection against reinfection with BA.2 (N=20,197; BA.1-against-BA.2 study), and effectiveness of BA.2 infection against reinfection with BA.1 (N=100,925; BA.2-against-BA.1 study). Associations were estimated using Cox proportional-hazards regression models. RESULTS: In the BA.1-against-BA.2 study, cumulative incidence of infection was estimated at 0.03% (95% CI: 0.01-0.07%) for the BA.1-infected cohort and at 0.62% (95% CI: 0.51-0.75%) for the uninfected-control cohort, 15 days after the start of follow-up. Effectiveness of BA.1 infection against reinfection with BA.2 was estimated at 94.9% (95% CI: 88.4-97.8%). In the BA.2-against-BA.1 study, cumulative incidence of infection was estimated at 0.03% (95% CI: 0.02-0.04%) for the BA.2-infected cohort and at 0.17% (95% CI: 0.15-0.21%) for the uninfected-control cohort, 15 days after the start of follow-up. Effectiveness of BA.2 infection against reinfection with BA.1 was estimated at 85.6% (95% CI: 77.4-90.9%). CONCLUSIONS: Infection with an Omicron sub-lineage appears to induce strong, but not full protection against reinfection with the other sub-lineage, for at least several weeks after the initial infection.

    🖺 Full Text HTML: Protection of Omicron sub-lineage infection against reinfection with another Omicron sub-lineage

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