Effectiveness of BNT162b2 COVID-19 vaccination in prevention of hospitalisations and severe disease in adults with SARS-CoV-2 Delta (B.1.617.2) and Omicron (B.1.1.529) variant between June 2021 and July 2022: A prospective test negative case-control study

Abstract

Background: Whilst other studies have reported the effectiveness of mRNA vaccination against hospitalisation, including emergency department or intensive care admission, few have assessed effectiveness against other more clinically robust indices of COVID-19 severity.

Methods: A prospective single-centre test-negative design case-control study of adults hospitalised with COVID-19 disease or other acute respiratory disease between 1 June 2021 and 20 July 2022. We assessed VE (vaccine effectiveness) against hospitalisation, length of stay [LOS] >3 days, WHO COVID Score >5 and supplementary oxygen FiO₂ (fraction inspired oxygen) >28%, conducting regression analyses controlling for age, gender, index of multiple deprivation, Charlson comorbidity index, time, and community infection prevalence.

Findings: 935 controls and 546 cases were hospitalised during the Delta period, with 721 controls and 372 cases hospitalised during the Omicron study period. Two-dose BNT162b2 was associated with VE 82.5% [95% confidence interval 76.2%-87.2%] against hospitalisation following Delta infection, 63.3% [26.9-81.8%], 58.5% [24.8-77.3%], and 51.5% [16.7-72.1%] against LOS >3 days, WHO COVID Score >5, and requirement for FiO2 >28% respectively. Three-dose BNT162b2 protection against hospitalisation with Omicron infection was 30.9% [5.9-49.3%], with sensitivity analyses ranging from 28.8-72.6%. Protection against LOS >3 days, WHO COVID Score >5 and requirement for FiO2 >28% was 56.1% [20.6-76.5%], 58.8% [31.2-75.8%], and 41.5% [-0.4-66.3%], respectively. In the UK, BNT162b2 was prioritised for high-risk individuals and those aged >75 years. In the latter group we found a higher estimate of VE against hospitalisation of 47.2% [16.8-66.6%].

Interpretation: BNT162b2 vaccination results in risk reductions for hospitalisation and multiple patient outcomes following Delta and Omicron COVID-19 infection, particularly in older adults. BNT162b2 remains effective against severe SARS-CoV-2 disease.

Funding: AvonCAP is an investigator-led project funded under a collaborative agreement by Pfizer.

Keywords: COVID-19; Respiratory infection; SARS-CoV-2; Vaccination.

Fig. 1

Study flow diagram. Inclusion and exclusion criteria in the cohort stratified by SARS-CoV-2 variant and restricted to BNT162b2 vaccine. Of the 546 SARS-CoV-2 positive individuals with known/inferred Delta variant, 90 were vaccinated with two-dose BNT162b2, 456 unvaccinated cases. There were 372 SARS-CoV-2 positive individuals with known/inferred Omicron variant: 182 vaccinated with three-dose BNT162b2, and 185 unvaccinated cases. Of the 935 SARS-CoV-2 negative individuals admitted during the Delta time period, 608 were vaccinated with two-dose BNT162b2 and 327 were unvaccinated cases. In the Omicron time period, 721 SARS-CoV-2 negative individuals were admitted: 410 vaccinated with three-dose BNT162b2 and 311 unvaccinated patients. ∗ During the Delta period, the controls include 51 individuals with 2 respiratory hospitalisations; 6 individuals who were admitted with three separate respiratory admissions, and one individual with 4 separate respiratory admissions. 93.8% of the controls (877/935) had only one respiratory hospitalisation. † In the Omicron period, the controls include 94 individuals with two respiratory admissions, 30 individuals with three separate respiratory admissions, 8 individuals with four separate respiratory admissions and 4 individuals with more than four separate respiratory admissions. 81.1% of the controls (585/721) had only one respiratory hospitalisation. Details of adults hospitalised with SARS-CoV-2 infection are provided in Supplementary Fig. S1. VOC, variant of concern.

Supplementary Fig. S1