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

Abstract

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.

Introduction

When COVID-19 vaccines were authorized and approved by the Food and Drug Administration (FDA) in the United States, the Centers for Disease Control and Prevention (CDC) began tracking cases, hospitalizations, and deaths among vaccinated persons [1]. The interpretability of this initial approach to COVID-19 vaccine breakthrough surveillance was hampered by limited reporting representativeness, a lack of denominators for rate calculations, and the absence of an unvaccinated comparison group. As state and local public health departments developed the capacity to routinely link case surveillance and immunization registry data, CDC collaborated with these jurisdictions to systematically monitor disease and mortality rates stratified by vaccination status [2]. Multi-jurisdictional surveillance data showed that COVID-19 vaccines provided strong protection against COVID-19-associated hospitalization and death in a period when the Delta variant was predominant [2]. A study during the Delta period showed evidence of waning protection against infection but strong protection against death 6 months after vaccination [3, 4]; these findings were similar to other published studies from Israel and the United States [5–8]. 

Materials methods

COVID-19 case data by vaccination status

We analyzed reported numbers of SARS-CoV-2 infections by age group (5–11, 12–17, 18–49, 50–64, ≥65 years of age) from 22 U.S. jurisdictions (AR, AZ, CA, CO, CT, DC, FL, GA, IN, KS, MI, MA, MN, NC, NE, NJ, NM, NYC, PHL, TN, UT, WI); ~53% of the U.S. population) with routine linkages between COVID-19 case surveillance and immunization information system (IIS) data reported to CDC during January 16, 2022 –May 28, 2022 through two different mechanisms. Nine jurisdictions reported line-level data for all COVID-19 cases, including date of specimen collection, vaccine product, and dates of vaccination; 13 jurisdictions reported line-level data on cases among vaccinated persons, together with aggregated weekly counts of cases among partially vaccinated and unvaccinated persons by age group and epidemiological week of the SARS-COV-2 positive test [12, 13]. A vaccinated person was defined as a person with SARS-CoV-2 RNA or antigen detected in a respiratory specimen collected ≥14 days after verifiably completing the primary series of an FDA-authorized or approved COVID-19 vaccine. An unvaccinated person was defined as a person who was not verified to have received any COVID-19 vaccine doses before the positive SARS-CoV-2 specimen collection date. Analyses were limited to the period January 16, 2022–May 28, 2022 when the Omicron variant was predominant. 

Results

Across 22 reporting jurisdictions, there were 4,409,632 persons ≥5 years old who were vaccinated but had not received a booster dose during January 16 to May 28, 2022 (Table 1). Since children were the last group to receive FDA authorization for COVID-19 vaccination, the majority of those vaccinated without a booster during this period were children ages 5–11 years (42%). There were 1,387,186 (34.4%), 1,203,904 (29.9%), 963,880 (23.9%), and 473,756 (11.8%) vaccinated persons during each of the four cohorts: (1) January 16–February 5, (2) February 6–26, (3) February 27–April 2, or (4) April 3–30, respectively. During January 16 to May 28, 2022, a total of 1,041 COVID-19 cases were reported per 100,000 vaccinated persons aged ≥5 years overall. The highest case rate was among children ages 5–11 years (1,384 cases per 100,000 vaccinated persons).

Discussion

This report describes the application of a life table analysis using COVID-19 case surveillance and vaccine administration data to evaluate the differences in hazard rates among people vaccinated and unvaccinated over time, which serves as a proxy of waning of vaccine protection against SARS-CoV-2 infection by age group during the Omicron period. At 19 weeks after vaccination, decreased protection against infection was observed for all age groups, residual protection against infection was observed for ages 12 and older. Children aged 5–11 years had similar hazard rates among vaccinated and unvaccinated cohorts at 14 weeks (or at 19 weeks in the sensitivity analysis), indicating limited vaccine protection against infection after these time points. Vaccine protection against severe COVID-19 outcomes was not evaluated but has been shown elsewhere to be more robust and durable than protection against infection and symptomatic disease [3, 4, 20–22].

Acknowledgments

We would like to acknowledge Aaron Bieringer, Miriam Muscoplat, Sydney Kuramoto, Amanda Markelz, Amy Saupe, Corinne Holtzman, Kathy Como-Sabetti, and Ruth Lynfield for their help in preparing advising on interpretation of these data.

Citation: Sternberg MR, Johnson A, King J, Ali AR, Linde L, Awofeso AO, et al. (2023) 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. PLoS ONE 18(9): e0291678. https://doi.org/10.1371/journal.pone.0291678

Editor: Barbara T. Rumain, Touro University, UNITED STATES

Received: March 8, 2023; Accepted: September 1, 2023; Published: September 20, 2023

This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

Data Availability: The data availability statement should be updated to say that all census data used for this study can be found at https://www2.census.gov/programs-surveys/popest/tables/2010-2019/state/asrh/ the file name used is sc-est2019-alldata6.csv.

Funding: The authors received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0291678#references