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BNT162b2 (Pfizer–Biontech) mRNA COVID-19 Vaccine Against Omicron-Related Hospital and Emergency Department Admission in a Large US Health System: A Test-Negative Design
25 Pages Posted: 18 Jan 2022More...
Background: Vaccine effectiveness (VE) against omicron is not well-characterized. We evaluated the effectiveness of two and three doses of BNT162b2 against hospital and ED admission for delta and omicron-related illness in a large US integrated health system.
Methods: Using a test-negative design, we analyzed electronic health records from members ≥18 years of age at Kaiser Permanente Southern California from Dec 01, 2021 through Jan 11, 2022. VE was calculated among those admitted to the hospital or emergency department (ED, without subsequent hospitalization) with COVID-19 symptoms using odds ratios from adjusted logistic regression models.
Findings: Analyses were conducted on 14,137 instances of hospital or ED admission for COVID-19-like illness where SARS-CoV-2 lineage could be determined. In adjusted VE analyses, protection from two doses against delta waned (ED: 80% [95% CI: 69−87] at <3 months to 63% [57−69] at ≥6 months; hospital admission: 88% (71−95) at <3 months to 74% (65−80) at ≥6 months). A third dose restored high VE against delta, with 88% (84−91) against ED and 93% (89−96) against hospital admission. VE of two or three doses of BNT162b2 was lower for omicron compared to delta. Protection against omicron-related ED admission waned after two doses, from 60% (43−72) at <3 months to 41% (32−50) at ≥6 months. VE of three doses against omicron-related ED admission also waned, from 78% (73−82) at <3 months to 48% (14−69) at ≥3 months. Against hospital admission, two-dose VE against omicron was 68% (58−75), and three-dose effectiveness was 89% (84−92). Waning of effectiveness against omicron-related hospitalization after two or three doses was not observed.
Interpretation: Up to four months following a third dose of BNT162b2, VE remained high (≥89%) against omicron-related hospitalization. Longer-term durability, however, remains unknown. Three doses of BNT162b2 were also effective at preventing omicron-related ED admission, however, protection waned for this milder form of disease. Additional doses of BNT162b2 or of omicron-targeted mRNA vaccines may be needed to maintain high levels of protection seen at earlier stages of the pandemic.
Trial Registration: This study was registered with NCT04848584.
Funding: Pfizer Inc.
Declaration of Interest: SRV, LJ, LP, and JMM are employees of and hold stock and/or stock options in Pfizer Inc. SYT, JMS, VH, and BA received research support from Pfizer during the conduct of this study that was paid directly to KPSC. All other authors report no conflicts.
Ethical Approval: The study protocol was reviewed and approved by the KPSC institutional review board which waived requirement for informed consent (number 12816).
Keywords: omicron, effectiveness, waning, booster, third dose, BNT162b2, SARS-CoV-2, COVID-19, United States, test-negative, kaiser
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