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Estimated Effectiveness of the BNT162b2 XBB Vaccine Against COVID-19
Sara Y Tartof1,2, Jeff M Slezak1, Timothy B Frankland3
1Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena.
Insights
The updated BNT162b2 XBB vaccine (Pfizer-BioNTech) significantly protects against COVID-19 hospitalization and emergency visits. Older COVID-19 vaccines offered minimal protection, underscoring the importance of annual updates.
Area of Science:
- Immunology
- Public Health
- Vaccinology
Background:
- Limited data exist on the early effectiveness of the BNT162b2 XBB vaccine (2023-2024 formulation).
- Understanding vaccine effectiveness is crucial for guiding public health recommendations and vaccine strategies.
Purpose of the Study:
- To estimate the effectiveness of the BNT162b2 XBB vaccine against medically attended COVID-19 outcomes in US adults.
- To compare the protection offered by the updated XBB vaccine versus older COVID-19 vaccine formulations.
Main Methods:
- A test-negative case-control study was conducted between October and December 2023.
- Adults presenting with acute respiratory illness were classified as cases (positive SARS-CoV-2 PCR) or controls (negative PCR).
- Logistic regression models were used to estimate adjusted odds ratios for vaccine effectiveness.
Main Results:
- The BNT162b2 XBB vaccine showed 62% effectiveness against COVID-19 hospitalization and 58% against emergency department/urgent care visits.
- Individuals vaccinated with older COVID-19 vaccine versions did not demonstrate a statistically significant reduced risk of COVID-19 outcomes compared to unvaccinated individuals.
Conclusions:
- The BNT162b2 XBB vaccine provides significant additional protection against COVID-19.
- Annually updated COVID-19 vaccines are recommended due to limited long-term protection from older formulations.
Importance:
Data describing the early additional protection afforded by the recently recommended BNT162b2 XBB vaccine (Pfizer-BioNTech; 2023-2024 formulation) are limited.
Objective:
To estimate the association between receipt of the BNT162b2 XBB vaccine and medically attended COVID-19 outcomes among US adults 18 years and older.
Design, Setting, And Participants:
This test-negative case-control study was performed to estimate the effectiveness of the BNT162b2 XBB vaccine against COVID-19-associated hospitalization and emergency department (ED) or urgent care (UC) encounters among adults in the Kaiser Permanente Southern California health system between October 10, 2023, and December 10, 2023. Cases were those presenting with an acute respiratory illness and who had a positive SARS-CoV-2 polymerase chain reaction test; controls had an acute respiratory illness but tested negative for SARS-CoV-2.
Exposure:
The primary exposure was receipt of the BNT162b2 XBB vaccine compared with not receiving an XBB vaccine of any kind, regardless of prior COVID-19 vaccination or SARS-CoV-2 infection history. Receipt of prior (non-XBB) versions of COVID-19 vaccines was also compared with being unvaccinated to estimate remaining protection from older vaccines.
Main Outcomes And Measures:
Analyses for cases and controls were conducted separately for COVID-19 hospital admissions and ED/UC encounters. Adjusted odds ratios and 95% CIs were estimated from multivariable logistic regression models that were adjusted for patient demographic and clinical characteristics. Estimation of vaccine effectiveness was calculated as 1 - odds ratio × 100%.
Results:
Among 2854 cases and 15 345 controls (median [IQR] age, 56 [37-72] years; 10 658 [58.6%] female), adjusted estimation of effectiveness of the BNT162b2 XBB vaccine received a median of 34 days prior vs not having received an XBB vaccine of any kind was 62% (95% CI, 32%-79%) against COVID-19 hospitalization and 58% (95% CI, 48%-67%) for ED/UC visits. Compared with being unvaccinated, those who had received only older versions of COVID-19 vaccines did not show statistically significant reduced risk of COVID-19 outcomes, including hospital admission.
Conclusions And Relevance:
Findings of this case-control study reaffirm current recommendations for broad age-based use of annually updated COVID-19 vaccines given that (1) the BNT162b2 XBB vaccine provided statistically significant additional protection against a range of COVID-19 outcomes and (2) older versions of COVID-19 vaccines offered little, if any, long-term protection, including against hospital admission, regardless of the number or type of prior doses received.
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