Waning of first- and second-dose ChAdOx1 and BNT162b2 COVID-19 vaccinations: a pooled target trial study of 12.9 million individuals in England, Northern Ireland, Scotland and Wales

Abstract

Background Several SARS-CoV-2 vaccines have been shown to provide protection against COVID-19 hospitalization and death. However, some evidence suggests that notable waning in effectiveness against these outcomes occurs within months of vaccination. We undertook a pooled analysis across the four nations of the UK to investigate waning in vaccine effectiveness (VE) and relative vaccine effectiveness (rVE) against severe COVID-19 outcomes. Methods We carried out a target trial design for first/second doses of ChAdOx1(Oxford–AstraZeneca) and BNT162b2 (Pfizer–BioNTech) with a composite outcome of COVID-19 hospitalization or death over the period 8 December 2020 to 30 June 2021. Exposure groups were matched by age, local authority area and propensity for vaccination. We pooled event counts across the four UK nations. Results For Doses 1 and 2 of ChAdOx1 and Dose 1 of BNT162b2, VE/rVE reached zero by approximately Days 60–80 and then went negative. By Day 70, VE/rVE was –25% (95% CI: –80 to 14) and 10% (95% CI: –32 to 39) for Doses 1 and 2 of ChAdOx1, respectively, and 42% (95% CI: 9 to 64) and 53% (95% CI: 26 to 70) for Doses 1 and 2 of BNT162b2, respectively. rVE for Dose 2 of BNT162b2 remained above zero throughout and reached 46% (95% CI: 13 to 67) after 98 days of follow-up. Conclusions We found strong evidence of waning in VE/rVE for Doses 1 and 2 of ChAdOx1, as well as Dose 1 of BNT162b2. This evidence may be used to inform policies on timings of additional doses of vaccine.

Effect of Age, Sex, and COVID-19 Vaccination History on All-Cause Mortality: Unexpected Outcomes in a Complex Biological and Social System

“…rVE for dose 2 of Pfizer remained above zero throughout and reached 46% after 98 days of follow-up [146]. This study broadly confirms potential negative vaccine effectiveness; however, it only covers COVID-19 confirmed hospitalization or death, i.e., not allcause mortality [179] .…”

“…Waning is a part of the real-world effects of both influenza [174,] and COVID-19 vaccination [175][176][177][178][179][180]. The waning of efficacy after COVID-19 vaccination will mostly affect the >21 days after vaccination group in Fig- ures A2.1 to A2.7.…”

Effectiveness and safety of coronavirus disease 2019 vaccines

“…VE of COVID-19 vaccination against confirmed SARS-CoV-2 infection and COVID-19 hospitalisation or death wanes over time [ 10 ]. Investigating vaccine waning was complicated by the emergence of new variants (specifically the Delta variant of concern in the UK).…”

Resilience to emerging infectious diseases and the importance of scientific innovation

“…The case cannot be clearer as we emerge from the COVID-19 pandemic. Multiple innovations were central to our response against COVID-19, including mass testing 1 and genomic tracking of the SARS-CoV-2 virus, 2 the creation of vaccines, 3 , 4 , 5 data linkage across health systems, modelling of the impact of public health interventions, 6 and the development of new treatments. 7 These scientific advances occurred at unprecedented pace and saved millions of lives.…”