Application of a life table approach to assess duration of BNT162b2 vaccine-derived immunity by age using COVID-19 case surveillance data during the Omicron variant period
Authors: Sternberg Maya R. , Johnson Amelia , King Justice , Ali Akilah R. , Linde Lauren , Awofeso Abiola O. , Baker Jodee S. , Bayoumi Nagla S. , Broadway Steven , Busen Katherine , Chang Carolyn , Cheng Iris , Cima Mike , Collingwood Abi , Dorabawila Vajeera , Drenzek Cherie , Fleischauer Aaron , Gent Ashley , Hartley Amanda , Hicks Liam , Hoskins Mikhail , Jara Amanda , Jones Amanda , Khan Saadiah I. , Kamal-Ahmed Ishrat , Kangas Sarah , Kanishka FNU , Kleppinger Alison , Kocharian Anna , León Tomás M. , Link-Gelles Ruth , Lyons B. Casey , Masarik John , May Andrea , McCormick Donald , Meyer Stephanie , Milroy Lauren , Morris Keeley J. , Nelson Lauren , Omoike Enaholo , Patel Komal , Pietrowski Michael , Pike Melissa A. , Pilishvili Tamara , Peterson Pompa Xandy , Powell Charles , Praetorius Kevin , Rosenberg Eli , Schiller Adam , Smith-Coronado Mayra L. , Stanislawski Emma , Strand Kyle , Tilakaratne Buddhi P. , Vest Hailey , Wiedeman Caleb , Zaldivar Allison , Silk Benjamin , Scobie Heather M. 
Published: September 2023

Background
SARS-CoV-2 Omicron variants have the potential to impact vaccine effectiveness and duration of vaccine-derived immunity. We analyzed U.S. multi-jurisdictional COVID-19 vaccine breakthrough surveillance data to examine potential waning of protection against SARS-CoV-2 infection for the Pfizer-BioNTech (BNT162b) primary vaccination series by age.

Methods
Weekly numbers of SARS-CoV-2 infections during January 16, 2022–May 28, 2022 were analyzed by age group from 22 U.S. jurisdictions that routinely linked COVID-19 case surveillance and immunization data. A life table approach incorporating line-listed and aggregated COVID-19 case datasets with vaccine administration and U.S. Census data was used to estimate hazard rates of SARS-CoV-2 infections, hazard rate ratios (HRR) and percent reductions in hazard rate comparing unvaccinated people to people vaccinated with a Pfizer-BioNTech primary series only, by age group and time since vaccination.

Results
The percent reduction in hazard rates for persons 2 weeks after vaccination with a Pfizer-BioNTech primary series compared with unvaccinated persons was lowest among children aged 5–11 years at 35.5% (95% CI: 33.3%, 37.6%) compared to the older age groups, which ranged from 68.7%–89.6%. By 19 weeks after vaccination, all age groups showed decreases in the percent reduction in the hazard rates compared with unvaccinated people; with the largest declines observed among those aged 5–11 and 12–17 years and more modest declines observed among those 18 years and older.

Conclusions
The decline in vaccine protection against SARS-CoV-2 infection observed in this study is consistent with other studies and demonstrates that national case surveillance data were useful for assessing early signals in age-specific waning of vaccine protection during the initial period of SARS-CoV-2 Omicron variant predominance. The potential for waning immunity during the Omicron period emphasizes the importance of continued monitoring and consideration of optimal timing and provision of booster doses in the future.