Vaccine Effectiveness Against Influenza-Associated Urgent Care, Emergency Department, and Hospital Encounters During the 2021-2022 Season, VISION Network.
J Infect Dis
; 228(2): 185-195, 2023 Jul 14.
Article
in English
| MEDLINE | ID: covidwho-2212818
ABSTRACT
BACKGROUND:
Following historically low influenza activity during the 2020-2021 season, the United States saw an increase in influenza circulating during the 2021-2022 season. Most viruses belonged to the influenza A(H3N2) 3C.2a1b 2a.2 subclade.METHODS:
We conducted a test-negative case-control analysis among adults ≥18 years of age at 3 sites within the VISION Network. Encounters included emergency department/urgent care (ED/UC) visits or hospitalizations with ≥1 acute respiratory illness (ARI) discharge diagnosis codes and molecular testing for influenza. Vaccine effectiveness (VE) was calculated by comparing the odds of influenza vaccination ≥14 days before the encounter date between influenza-positive cases (type A) and influenza-negative and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-negative controls, applying inverse probability-to-be-vaccinated weights, and adjusting for confounders.RESULTS:
In total, 86 732 ED/UC ARI-associated encounters (7696 [9%] cases) and 16 805 hospitalized ARI-associated encounters (649 [4%] cases) were included. VE against influenza-associated ED/UC encounters was 25% (95% confidence interval (CI), 20%-29%) and 25% (95% CI, 11%-37%) against influenza-associated hospitalizations. VE against ED/UC encounters was lower in adults ≥65 years of age (7%; 95% CI, -5% to 17%) or with immunocompromising conditions (4%; 95% CI, -45% to 36%).CONCLUSIONS:
During an influenza A(H3N2)-predominant influenza season, modest VE was observed. These findings highlight the need for improved vaccines, particularly for A(H3N2) viruses that are historically associated with lower VE.Keywords
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Main subject:
Influenza Vaccines
/
Influenza, Human
/
Influenza A Virus, H1N1 Subtype
/
COVID-19
Type of study:
Experimental Studies
/
Observational study
/
Prognostic study
Topics:
Vaccines
Limits:
Adult
/
Child, preschool
/
Humans
Country/Region as subject:
North America
Language:
English
Journal:
J Infect Dis
Year:
2023
Document Type:
Article
Affiliation country:
Infdis
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