Vaccine effectiveness and duration of protection of Comirnaty, Vaxzevria and Spikevax against mild and severe COVID-19 in the UK (preprint)

ABSTRACT

BackgroundCOVID-19 vaccines have been used for 9 months in the UK. Real world data have demonstrated the vaccines to be highly effective against COVID-19, severe disease and death. Here, we estimate vaccine effectiveness over time since the second dose of Comirnaty, Vaxzevria and Spikevax in England. MethodsWe used a test-negative case-control design to estimate vaccine effectiveness against symptomatic disease, hospitalisation and mortality by age, comorbidity status and over time after the second dose to investigate waning separately for Alpha and Delta variants. ResultsVaccine effectiveness against symptomatic disease peaked in the early weeks after the second dose and then fell to 47.3 (95% CI 45 to 49.6) and 69.7 (95% CI 68.7 to 70.5) by 20+ weeks against the Delta variant for Vaxzevria and Comirnaty, respectively. Waning of vaccine effectiveness was greater for 65+ year-olds compared to 40-64 year-olds. Vaccine effectiveness fell less against hospitalisations to 77.0 (70.3 to 82.3) and 92.7 (90.3 to 94.6) beyond 20 weeks post-vaccination and 78.7 (95% CI 52.7 to 90.4) and 90.4 (95% CI 85.1 to 93.8) against death for Vaxzevria and Comirnaty, respectively. Greater waning was observed among 65+ year-olds in a clinically extremely vulnerable group and 40-64-year olds with underlying medical conditions compared to healthy adults. ConclusionsWe observed limited waning in vaccine effectiveness against hospitalisation and death more than 20 weeks post-vaccination with Vaxzevria or Comirnaty. Waning was greater in older adults and those in a clinical risk group, suggesting that these individuals should be prioritised for booster doses.