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Pfizer-BioNTech and AstraZeneca vaccines offer high protection against severe COVID-19, six months after second doses, study finds

Press release issued: 20 July 2022

Protection against severe COVID-19 by two doses of Pfizer-BioNTech and AstraZeneca COVID-19 vaccines remained high up to six months after second doses, finds new research which analysed NHS health record data on over seven million adults. Reassuringly, the University of Bristol-led study published in The BMJ today [July 20], found protection in older adults aged over 65 years, and in clinically vulnerable adults.

Researchers from Bristol Medical School, Oxford University and the London School of Hygiene and Tropical Medicine sought to investigate how quickly vaccine effectiveness waned over time in adults without prior SARS-CoV-2 infection and who received two doses of BNT162b2 (Pfizer-BioNTech) or ChAdOx1 (AstraZeneca) COVID-19 vaccine compared with unvaccinated individuals. 

Rates of COVID-19 hospital admission and COVID-19 death were substantially lower among vaccinated than unvaccinated adults up to six months after their second dose.  Vaccine effectiveness against these events was found to be at least 80 per cent for BNT162b2, and at least 75 per cent for ChAdOx1. However, waning vaccine effectiveness against infection with SARS-CoV-2 meant that rates in vaccinated individuals were similar to or higher than in unvaccinated individuals by six months after the second dose. 

Paper: 'Waning effectiveness of BNT162b2 and ChAdOx1 covid-19 vaccines over six months since second dose: OpenSAFELY cohort study using linked electronic health records' by E Horne et al. in The BMJ [open access]

Read the full University of Bristol press release

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