Effects of BNT162b2 mRNA vaccine on COVID-19 infection and hospitalisation amongst older people: matched case control study for England
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Abstract
Background
The BNT162b2 mRNA vaccine has been shown to be effective at preventing serious COVID-19 events in clinical trials. There is less evidence on effectiveness in real-world settings, especially for older people. Here, we aimed to estimate vaccine effectiveness in the context of the rapid NHS mass-vaccination programme in England, exploiting age-based vaccination eligibility thresholds to minimise and correct for selection bias.
Methods
We studied 170,226 individuals between the ages of 80 and 83 years from community settings outside care homes who received one dose of BNT162b2 mRNA between the 15 and 20 December 2020 and were scheduled a second dose 21 days later. We matched these vaccine recipients to slightly younger (aged 76–79 years) persons not yet eligible to receive the vaccine on gender, area of residence, area deprivation, health status, living arrangements, acute illness, and history of seasonal flu vaccination. We compared their rates of COVID-19 positivity and hospitalisation in the subsequent 45 days. We adjusted for the increasing concentration of COVID-19 positivity in the control population caused by the requirement to have no COVID-19 symptoms prior to vaccination.
Results
Emergency hospital admissions were 51.0% (95% confidence interval 19.9 to 69.5%) lower and positive COVID-19 tests were 55.2% (40.8 to 66.8%) lower for vaccinated individuals compared to matched controls 21 to 27 days after first vaccination. Emergency admissions were 75.6% (52.8 to 87.6%) lower, and positive COVID-19 tests were 70.1% (55.1 to 80.1%) lower 35 to 41 days after first vaccination when 79% of participants had received a second dose within 26 days of their first dose.
Conclusions
Receipt of the BNT162b2 mRNA vaccine is effective at reducing COVID-19 hospitalisations and infections. The nationwide vaccination of older adults in England with the BNT162b2 mRNA vaccine reduced the burden of COVID-19.
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SciScore for 10.1101/2021.04.19.21255461: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: Thank you for sharing your code.
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Strengths and weaknesses of the study: We focused on a large number of the oldest people at high risk of serious Covid-19 outcomes. We considered a period and country experiencing widespread transmission and large numbers of hospitalisations. This provided statistical precision in the effectiveness estimates within a short period. We exploited a precise age cut-off that determined access to the vaccine, which reduced bias from selection into …
SciScore for 10.1101/2021.04.19.21255461: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: Thank you for sharing your code.
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Strengths and weaknesses of the study: We focused on a large number of the oldest people at high risk of serious Covid-19 outcomes. We considered a period and country experiencing widespread transmission and large numbers of hospitalisations. This provided statistical precision in the effectiveness estimates within a short period. We exploited a precise age cut-off that determined access to the vaccine, which reduced bias from selection into treatment. Nonetheless, there is a risk of bias from unmeasured confounding. We matched cases and controls on combinations of 12 personal, household and area variables. We also compared four measures of hospital use in the previous 18 months and history of negative SARS-CoV-2 tests (see Appendix 6). Cases did not have lower event rates and had higher use of hospital services and more community-based Covid-19 tests prior to vaccination. This likely reflects the age difference which may bias our estimates towards lower than true effectiveness. The rich set of matching variables meant some cases were excluded because there was no control available. These exclusions were more likely for some populations, including minority ethnic groups and residents of London, but the included individuals had similar outcomes to the excluded individuals and the effectiveness results were similar when we matched on fewer variables (Appendix 4). The speed of the rollout of the NHS vaccination programme in England into younger populations reduced the pool of si...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- No funding statement was detected.
- No protocol registration statement was detected.
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