Pfizer-BioNTech COVID-19 Vaccine Effectiveness Study - Kaiser Permanente Southern California

NCT04848584 | Completed FDA Drug

• 2 other identifiers: C4591014NCT04848584
• Study Type: observational
• Target: 1
• Locations: 1 country
• Sites: 1

Brief Summary

The primary objective of this study is to determine the vaccine effectiveness of 2 doses of Pfizer-BioNTech BNT162b2 vaccine against COVID-19-associated hospitalization. There will be a large retrospective database study using two parallel study designs: a test-negative case-control design and a retrospective cohort design. VE estimates by various strata and strain type will be conducted.

Conditions

COVID-19

Outcome Measures

Primary Outcomes (6)

• Test Negative Design Outcome: VE calculated as 1 minus the odds ratio (OR) comparing the odds of being vaccinated with 2 doses with BNT162b2 for hospitalized cases and controls, multiplied by 100%.

  To estimate the effectiveness of 2 doses of BNT162b2 against hospitalization for Acute Respiratory Infection due to SARS-CoV-2 infection

  up to three years

• Cohort Design Outcome: VE calculated as 1 minus the hazard ratio (HR) comparing the incidence of 2 doses with BNT162b2 for hospitalization due to SARS-CoV-2 infection and not, multiplied by 100%.

  To estimate the effectiveness of 2 doses of BNT162b2 against hospitalization due to SARS-CoV-2 infection

  up to three years

• VE of XBB.1.5-adapted monovalent vaccine against hospitalization

  chart reviews focused on the identification of hospitalizations that are clearly not for COVID-19.

  up to three years

• VE of XBB.1.5-adapted monovalent vaccine against critical illness

  Chart confirmed COVID-19 related to critical illness (death, mechanical ventilation, ICU)

  up to three years

• VE of XBB.1.5-adapted monovalent against outpatient visits

  Number of patients with identified acute respiratory illness (ARI) diagnosis

  up to three years

• VE of XBB.1.5-adapted monovalent vaccine against UC/ED visits.

  Number of patients with identified acute respiratory illness (ARI) diagnosis

  up to three years

Secondary Outcomes (21)

• Test Negative Design Outcome: VE calculated as 1 minus the OR comparing the odds of being vaccinated with 2 doses BNT162b2 for ED cases and controls, multiplied by 100%

  up to three years

• Test Negative Design Outcome: VE calculated as 1 minus the OR comparing the odds of being partially vaccinated with BNT162b2 (only 1 dose) for hospitalized cases and controls, multiplied by 100%.

  up to three years

• Test Negative Design Outcome: VE calculated as 1 minus the OR comparing the odds of being partially vaccinated with BNT162b2 (only 1 dose) for ED cases and controls, multiplied by 100%.

  up to three years

• Test Negative Design Outcome: VE calculated as 1 minus the OR comparing the odds of ever being vaccinated (≥1 dose) with BNT162b2 for hospitalized cases and controls, multiplied by 100%.

  up to three years

• Test Negative Design Outcome: VE calculated as 1 minus the OR comparing the odds of ever being vaccinated (≥1 dose) with BNT162b2 for ED cases and controls, multiplied by 100%.

  up to three years

Study Arms (7)

Fully vaccinated

Prior receipt of 2 doses of BNT162b2 received with ≥7 days between receipt of the 2nd dose and the index date. This group will serve as the 'exposed' group evaluated in the primary objective.

Biological: Primary Exposure Status of Pfizer-BioNTech COVID-19 Vaccine; Biological: BNT162b2 BA.4/5 bivalent

Partially vaccinated

Prior receipt of 1 dose (only) of BNT162b2 received with ≥14 days between receipt of the 1st dose and the index date.

Biological: Primary Exposure Status of Pfizer-BioNTech COVID-19 Vaccine; Biological: BNT162b2 BA.4/5 bivalent

Ever vaccinated

Prior receipt ≥1 dose of BNT162b2 received with ≥14 days between index date and receipt of the 1st dose

Biological: Primary Exposure Status of Pfizer-BioNTech COVID-19 Vaccine

Never vaccinated

never received BNT162b2. This group will serve as the reference exposure group (i.e., 'unexposed' group) in all VE analyses

Biological: Primary Exposure Status of Pfizer-BioNTech COVID-19 Vaccine; Biological: BNT162b2 BA.4/5 bivalent

Bivalent vaccinated

Receipt of the BNT162b2 BA.4/5 bivalent vaccine ≥8 weeks (≥56 days) since the most recent dose of wild-type COVID-19 mRNA vaccine (BNT162b2 or mRNA-1273) received

Biological: BNT162b2 BA.4/5 bivalent

XBB.1.5 vaccinated

Receipt of XBB.1.5-adapted monovalent vaccine with greater than or equal 14 days between receipt of vaccine and the event date.

Biological: XBB.1.5-adapted vaccinated

Unexposed to XBB.1.5

Unvaccinated with XBB.1.5-adapted monovalent vaccine or any other manufacturer's XBB-adapted formulation.

Biological: XBB.1.5-adapted vaccinated

Interventions

Primary Exposure Status of Pfizer-BioNTech COVID-19 Vaccine BIOLOGICAL

prior administration of Pfizer-BioNTech COVID-19 vaccine; vaccine is not administered in this study

Also known as: COVID VACCINE

Ever vaccinated; Fully vaccinated; Never vaccinated; Partially vaccinated

BNT162b2 BA.4/5 bivalent BIOLOGICAL

Vaccination with a bivalent booster was defined as receipt of the BNT162b2 BA 4/5 bivalent vaccine ≥8 weeks (≥56 days) since the most recent dose of wild-type COVID-19 mRNA vaccine (BNT162b2 or mRNA-1273) received.

Bivalent vaccinated; Fully vaccinated; Never vaccinated; Partially vaccinated

XBB.1.5-adapted vaccinated BIOLOGICAL

Vaccinated with XBB.1.5-adapted vaccine

Unexposed to XBB.1.5; XBB.1.5 vaccinated

Eligibility Criteria

• Age: 0 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

All members of KPSC who are eligible based on vaccination status and age.

You may qualify if:

• KPSC patients eligible to receive BNT162b2 who are admitted to the hospital (primary objective and some secondary objectives) with acute respiratory infection (ARI; International Classification of Diseases (ICD) codes) after 14 December 2020 (date of first vaccinations at KPSC), and who receive a PCR test for SARS-CoV-2.
• For secondary objectives estimating VE against ED admission, the TND will include KPSC patients eligible to receive BNT162b2 who present to the ED with ARI after 14 December 2020, and who receive a PCR test for SARS-CoV-2.
• We will include membership requirement of 1 year prior to index date, which is defined as the date of hospitalization or ED admission (allowing 31-day administrative gap), to facilitate accurate capture of comorbid conditions.
• All KPSC members as of 14 December 2020 (date of first Pfizer vaccination at KPSC) eligible to receive BNT162b2.
• For the cohort study, patients must have at least 1 year of membership (allowing 31-day administrative gap) prior to 14 December 2020 (index date, date vaccinations first began at KPSC) to facilitate accurate capture of comorbid conditions.

You may not qualify if:

• XBB.1.5-adapted monovalent vaccine eligibility analyses:
• KPSC membership for a minimum of 1 year prior to index date, allowing a 30-day gap in membership to allow for delays in renewal. Participants \<1 year did not have a membership requirement.≥6 months of age as of index date
• Admitted to the hospital or had an encounter in the ED, UC, or OP setting with a diagnosis of acute respiratory infection (ARI; defined based on International Classification of Diseases (ICD) codes listed in Appendix Table 1) after 25 September 2023
• Received a SARS-CoV-2 PCR or rapid antigen test
• Individuals who received a non-Pfizer-BioNTech XBB.1.5-adapted monovalent vaccine
• Individuals with an index event \<14 days after vaccination with Pfizer-BioNTech XBB.1.5-adapted monovalent vaccine
• Individuals receiving a mRNA bivalent BA4.5 booster ≤ 8 weeks (≤ 56 days) since receiving last wild type dose
• Individuals with \<28 days between a second and subsequent wild type dose
• Individuals receiving a XBB.1.5-adapted monovalent vaccine ≤ 8 weeks (≤ 56 days) since receiving a mRNA bivalent BA4.5 booster
• Individuals receiving oral COVID-19 antiviral OP treatments within 30 days of index event (will be excluded for primary analysis, but included in sensitivity analyses)

Sponsors & Collaborators

• Pfizer: lead

Study Sites (1)

Kaiser Permanente Southern California

Pasadena, California, 91101, United States

Location

Related Publications (4)

• Tartof SY, Slezak JM, Puzniak L, Hong V, Frankland TB, Ackerson BK, Xie F, Takhar H, Ogun OA, Simmons S, Zamparo JM, Valluri SR, Jodar L, McLaughlin JM. Effectiveness of BNT162b2 BA.4/5 bivalent mRNA vaccine against a range of COVID-19 outcomes in a large health system in the USA: a test-negative case-control study. Lancet Respir Med. 2023 Dec;11(12):1089-1100. doi: 10.1016/S2213-2600(23)00306-5. Epub 2023 Oct 25.

  PMID: 37898148 DERIVED

• Tartof SY, Slezak JM, Puzniak L, Hong V, Frankland TB, Xie F, Ackerson BK, Valluri SR, Jodar L, McLaughlin JM. Effectiveness and durability of BNT162b2 vaccine against hospital and emergency department admissions due to SARS-CoV-2 omicron sub-lineages BA.1 and BA.2 in a large health system in the USA: a test-negative, case-control study. Lancet Respir Med. 2023 Feb;11(2):176-187. doi: 10.1016/S2213-2600(22)00354-X. Epub 2022 Oct 7.

  PMID: 36216013 DERIVED

• Tartof SY, Slezak JM, Puzniak L, Hong V, Xie F, Ackerson BK, Valluri SR, Jodar L, McLaughlin JM. Durability of BNT162b2 vaccine against hospital and emergency department admissions due to the omicron and delta variants in a large health system in the USA: a test-negative case-control study. Lancet Respir Med. 2022 Jul;10(7):689-699. doi: 10.1016/S2213-2600(22)00101-1. Epub 2022 Apr 22.

  PMID: 35468336 DERIVED

• Tartof SY, Slezak JM, Fischer H, Hong V, Ackerson BK, Ranasinghe ON, Frankland TB, Ogun OA, Zamparo JM, Gray S, Valluri SR, Pan K, Angulo FJ, Jodar L, McLaughlin JM. Effectiveness of mRNA BNT162b2 COVID-19 vaccine up to 6 months in a large integrated health system in the USA: a retrospective cohort study. Lancet. 2021 Oct 16;398(10309):1407-1416. doi: 10.1016/S0140-6736(21)02183-8. Epub 2021 Oct 4.

  PMID: 34619098 DERIVED

Related Links

• To obtain contact information for a study center near you, click here.

MeSH Terms

Conditions

COVID-19

Condition Hierarchy (Ancestors)

Pneumonia, Viral; Pneumonia; Respiratory Tract Infections; Infections; Virus Diseases; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; RNA Virus Infections; Lung Diseases; Respiratory Tract Diseases

Study Officials

• Pfizer CT.gov Call Center

  Pfizer

  STUDY DIRECTOR

Study Design

• Study Type: observational
• Observational Model: CASE CONTROL
• Time Perspective: RETROSPECTIVE
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: March 30, 2021
• First Posted: April 19, 2021
• Study Start: May 15, 2021
• Primary Completion: April 30, 2025
• Study Completion: April 30, 2025
• Last Updated: July 29, 2025

Record last verified: 2025-07

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)