Effectiveness of BNT162b2 booster doses in England: an observational study in OpenSAFELY-TPP

Effectiveness of BNT162b2 booster doses in England: an observational study in OpenSAFELY-TPP

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How to cite: William J Hulme, Elizabeth J Williamson, Elsie Horne, Amelia CA Green, Linda Nab, Ruth Keogh, Edward PK Parker, Venexia M Walker, Tom M Palmer, Helen J Curtis, Milan Wiedemann, Christine Cunningham, Alex J Walker, Louis Fisher, Brian MacKenna, Christopher T Rentsch, Anna Schultze, Krishnan Bhaskaran, John Tazare, Laurie A Tomlinson, Helen I McDonald, Caroline E Morton, Richard Croker, Colm D Andrews, Lisa EM Hopcroft, Robin Y Park, Jon Massey, Amir Mehrkar, Jessica Morley, Sebastian CJ Bacon, David Evans, Peter Inglesby, George Hickman, Simon Davy, Iaim Dillingham, Tom Ward, Viyaasan Mahalingasivam, Bang Zheng, Ian J Douglas, Stephen JW Evans, Christopher Bates, Jonathan AC Sterne, Miguel A Hernan, Ben Goldacre medRxiv 2022.06.06.22276026

Abstract

Background:

The UK COVID-19 vaccination programme delivered its first “booster” doses in September 2021, initially in groups at high risk of severe disease then across the adult population. The BNT162b2 Pfizer-BioNTech vaccine was used initially, with Moderna mRNA-1273 subsequently also used.

Methods:

We used the OpenSAFELY-TPP database, covering 40% of English primary care practices and linked to national coronavirus surveillance, hospital episodes, and death registry data, to estimate the effectiveness of boosting with BNT162b2 compared with no boosting in eligible adults who had received two primary course vaccine doses between 16 September and 16 December 2021 when the Delta variant of SARS-CoV-2 was dominant. Follow up was for up to 10 weeks. Each booster recipient was matched with an unboosted control on factors relating to booster priority status and prior immunisation. Additional factors were adjusted for in Cox models estimating hazard ratios (HRs). Outcomes were positive SARS-CoV-2 test, COVID-19 hospitalisation, COVID-19 death and non-COVID-9 death. Booster vaccine effectiveness was defined as 1−HR.

Results:

Among 4,352,417 BNT162b2 booster recipients matched with unboosted controls, estimated effectiveness of a booster dose compared with two doses only was 50.7% (95% CI 50.1-51.3) for positive SARS-CoV-2 test, 80.1% (78.3-81.8) for COVID-19 hospitalisation, 88.5% (85.0-91.1) for COVID-19 death, and 80.3% (79.0-81.5) for non-COVID-19 death. Estimated effectiveness was similar among those who had received a BNT162b2 or ChAdOx1-S two-dose primary vaccination course, but effectiveness against severe COVID-19 was slightly lower in those classified as clinically extremely vulnerable (76.3% (73.1-79.1) for COVID-19 hospitalisation, and 85.1% (79.6-89.1) for COVID-19 death). Estimated effectiveness against each outcome was lower in those aged 18-65 years than in those aged 65 and over.

Conclusions:

Our findings are consistent with strong protection of BNT162b2 boosting against positive SARS-CoV-2 test, COVID-19 hospitalisation, and COVID-19 death.