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. 2022 Aug 25;75(2):230-238.
doi: 10.1093/cid/ciab931.

Vaccine Effectiveness Against Life-Threatening Influenza Illness in US Children

Samantha M Olson  1 , Margaret M Newhams  2 , Natasha B Halasa  3 , Leora R Feldstein  1 , Tanya Novak  2   4 , Scott L Weiss  5 , Bria M Coates  6 , Jennifer E Schuster  7 , Adam J Schwarz  8 , Aline B Maddux  9 , Mark W Hall  10 , Ryan A Nofziger  11 , Heidi R Flori  12 , Shira J Gertz  13 , Michele Kong  14 , Ronald C Sanders  15 , Katherine Irby  15 , Janet R Hume  16 , Melissa L Cullimore  17 , Steven L Shein  18 , Neal J Thomas  19 , Laura S Stewart  3 , John R Barnes  1 , Manish M Patel  1 , Adrienne G Randolph  2   4   20 ; Pediatric Intensive Care Influenza Investigators
Collaborators, Affiliations

Vaccine Effectiveness Against Life-Threatening Influenza Illness in US Children

Samantha M Olson et al. Clin Infect Dis. .

Abstract

Background: Predominance of 2 antigenically drifted influenza viruses during the 2019-2020 season offered an opportunity to assess vaccine effectiveness against life-threatening pediatric influenza disease from vaccine-mismatched viruses in the United States.

Methods: We enrolled children aged <18 years admitted to the intensive care unit with acute respiratory infection across 17 hospitals. Respiratory specimens were tested using reverse-transcription polymerase chain reaction for influenza viruses and sequenced. Using a test-negative design, we estimated vaccine effectiveness comparing odds of vaccination in test-positive case patients vs test-negative controls, stratifying by age, virus type, and severity. Life-threating influenza included death or invasive mechanical ventilation, vasopressors, cardiopulmonary resuscitation, dialysis, or extracorporeal membrane oxygenation.

Results: We enrolled 159 critically ill influenza case-patients (70% ≤8 years; 51% A/H1N1pdm09 and 25% B-Victoria viruses) and 132 controls (69% were aged ≤8 years). Among 56 sequenced A/H1N1pdm09 viruses, 29 (52%) were vaccine-mismatched (A/H1N1pdm09/5A+156K) and 23 (41%) were vaccine-matched (A/H1N1pdm09/5A+187A,189E). Among sequenced B-lineage viruses, majority (30 of 31) were vaccine-mismatched. Effectiveness against critical influenza was 63% (95% confidence interval [CI], 38% to 78%) and similar by age. Effectiveness was 75% (95% CI, 49% to 88%) against life-threatening influenza vs 57% (95% CI, 24% to 76%) against non-life-threating influenza. Effectiveness was 78% (95% CI, 41% to 92%) against matched A(H1N1)pdm09 viruses, 47% (95% CI, -21% to 77%) against mismatched A(H1N1)pdm09 viruses, and 75% (95% CI, 37% to 90%) against mismatched B-Victoria viruses.

Conclusions: During a season when vaccine-mismatched influenza viruses predominated, vaccination was associated with a reduced risk of critical and life-threatening influenza illness in children.

Keywords: case control; influenza; pediatrics; severity; vaccination.

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Conflict of interest statement

Potential conflicts of interest. J. R. B. reports CDC program funds outside of the submitted work. B. M. C. reports payments to their institution from the National Institutes of Health (NIH), National Heart, Lung, and Blood Institutes, American Thoracic Society, and American Lung Association outside of the submitted work. M. W. H. reports royalties or licenses from Kiadis and participation on a data safety monitoring board or advisory board for La Jolla Pharmaceuticals. M. K. reports grants or contracts made to their institution from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01). R. A. N. reports funding to their institution as a subaward from the CDC and NIH. A. G. R. reports royalties or licenses from UpToDate for section editor pediatric critical care; payment for expert testimony for a sepsis-related case; unpaid role as a council member of the International Sepsis Forum; and unpaid role as medical board member of Families Fighting Flu. J. E. S. reports money paid to their institution from Merck and the NIH outside of the submitted work. N. J. T. reports payments to Penn State from the CDC outside of the submitted work. S. L. W. reports funds made to their institution from the NIH and Pennsylvania Department of Health outside of the submitted work and being a Data and Safety Monitoring Board (DSMB) member for the Oxy-PICU Clinical Trial. N. B. H. reports grants or contracts to their institution from Sanofi and Quidel; an educational grant funded by genetech; and healthcare-associated infections and vaccine donation from Sanofi for a vaccine study. J. R. H. reports DSMB for institutional study at the University of Minnesota (“Magnesium sulfate as adjuvant analgesia and its effect on opiate use by post-operative transplant patients in the pediatric ICU”) for magnesium sulfate as an investigational new drug per the US Food and Drug Administration with no financial reimbursements. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

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