Background:
Omicron and its sublineages have comprised of the majority of SARS-CoV-2 genomes sequenced by the Centers for Disease Control and Prevention (CDC) since December 2021. KP.2 was first identified as a circulating variant under monitoring (VUM) by the World Health Organization in March 2024. FLiRT-mutated subvariants (including KP.2 and recent FluQE-mutated subvariants) have been the predominant variants sequenced in the US throughout 2024. FLiRT-mutated sub-lineages are antigenically distant from prior circulating SARS-CoV-2 lineages, including Omicron XBB, Omicron BA.4/BA.5 and the original SARS-CoV-2 wild-type strain. While Omicron XBB-adapted vaccines provide some protection against a range of outcomes from FLiRT-mutated-related COVID-19, evidence suggests that vaccines better matched to currently circulating sub-lineages can help further improve protection against symptomatic disease and severe COVID-19. Following guidance from regulatory authorities on the requirements for strain changes, Pfizer/BioNTech filed data showing that the FLiRT-mutated-adapted (KP.2) monovalent COVID-19 vaccine generates improved responses against circulating sublineages, compared to the 2023-2024 Omicron XBB-adapted COVID-19 vaccine. On June 27, 2024, the Advisory Committee on Immunization Practices recommended an updated 2024-2025 COVID-19 vaccine for all persons aged ≥6 months, regardless of prior vaccination history. On August 22nd 2024, FDA approved the KP.2 strain COVID-19 vaccine (2024-2025 Formula) for those aged \>12 years ages and authorized its use in those 6 months through 11 years of age.
Research Question:
What is the real-world effectiveness of the Pfizer/BioNTech 2024-2025 formulation of the COVID-19 vaccine against symptomatic COVID-19, across different age groups, during periods when different subvariants are circulating, and by months since receipt of the 2024-2025 formulated COVID-19 vaccine dose?
Research Methods:
Population: In collaboration with CVS, Pfizer will conduct a retrospective study to analyze patients tested for SARS-CoV-2 on or after September 5th, 2024, which corresponds with 14 days following FDA approval of the 2024-2025 updated COVID-19 vaccine. CVS will leverage CVS MinuteClinic data on patients ≥5 years of age who are testing for SARS-CoV-2 to evaluate the effectiveness of the 2024-2025 Pfizer/BioNTech COVID-19 vaccine formulation against symptomatic SARS-CoV-2 infection.
Exposure: The exposure of interest will be receipt of the Pfizer-BioNTech BNT162b2 COVID-19 vaccine (2024-2025 formulation) ≥14 days before testing for SARS-CoV-2. The reference group for the overall VE will be no receipt of the Pfizer-BioNTech BNT162b2 COVID-19 vaccine (2024-2025 formulation) or any other 2024-2025 formulated COVID-19 vaccine regardless of prior vaccination history.
Outcome: Cases will be defined as patients testing positive for SARS-CoV-2 infection by RAT at a CVS MinuteClinic and reporting at least one COVID-19 symptom. Controls will be defined as participants testing negative for SARS-CoV-2 by RAT at a CVS MinuteClinic and reporting at least one COVID-19 symptom during the same period.
Calculation: Estimated vaccine effectiveness will be calculated as 1 minus the odds ratio from logistic regression models multiplied by 100.
