Influenza Vaccine Effectiveness for Prevention of Severe Influenza-Associated Illness Among Adults in the United States, 2019-2020: A Test-Negative Study.
Clin Infect Dis
; 73(8): 1459-1468, 2021 10 20.
Article
in En
| MEDLINE
| ID: mdl-34014274
ABSTRACT
BACKGROUND:
Influenza vaccine effectiveness (VE) against a spectrum of severe disease, including critical illness and death, remains poorly characterized.METHODS:
We conducted a test-negative study in an intensive care unit (ICU) network at 10 US hospitals to evaluate VE for preventing influenza-associated severe acute respiratory infection (SARI) during the 2019-2020 season, which was characterized by circulation of drifted A/H1N1 and B-lineage viruses. Cases were adults hospitalized in the ICU and a targeted number outside the ICU (to capture a spectrum of severity) with laboratory-confirmed, influenza-associated SARI. Test-negative controls were frequency-matched based on hospital, timing of admission, and care location (ICU vs non-ICU). Estimates were adjusted for age, comorbidities, and other confounders.RESULTS:
Among 638 patients, the median (interquartile) age was 57 (44-68) years; 286 (44.8%) patients were treated in the ICU and 42 (6.6%) died during hospitalization. Forty-five percent of cases and 61% of controls were vaccinated, which resulted in an overall VE of 32% (95% CI 2-53%), including 28% (-9% to 52%) against influenza A and 52% (13-74%) against influenza B. VE was higher in adults 18-49 years old (62%; 95% CI 27-81%) than those aged 50-64 years (20%; -48% to 57%) and ≥65 years old (-3%; 95% CI -97% to 46%) (Pâ =â .0789 for interaction). VE was significantly higher against influenza-associated death (80%; 95% CI 4-96%) than nonfatal influenza illness.CONCLUSIONS:
During a season with drifted viruses, vaccination reduced severe influenza-associated illness among adults by 32%. VE was high among young adults.Key words
Full text:
1
Database:
MEDLINE
Main subject:
Influenza Vaccines
/
Influenza, Human
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Influenza A Virus, H1N1 Subtype
Type of study:
Observational_studies
/
Risk_factors_studies
Limits:
Adolescent
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Adult
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Aged
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Humans
/
Middle aged
Country/Region as subject:
America do norte
Language:
En
Journal:
Clin Infect Dis
Journal subject:
DOENCAS TRANSMISSIVEIS
Year:
2021
Type:
Article
Affiliation country:
United States