October 4, 2022Open Access
A Multi-Center, Controlled Human Infection Study of Influenza A (H1N1)pdm09 in Healthy Adults
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Key result
Every two-fold increase in baseline hemagglutination inhibition titer was associated with a non-significant 19% decrease in the odds of developing mild-to-moderate influenza disease (OR 0.81).
Why the study?
Influenza controlled human infection model studies can advance development of vaccines and therapeutics, but the associations between baseline challenge virus-specific HAI and MN titers and subsequent symptomatic infection needed evaluation.
Population
76 healthy adults aged 18 through 49 years
Comparison
Baseline HAI and MN titers ≥40 vs <40
Design
Multisite controlled human infection model study
Authors
Discussion
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Implication
Higher baseline HAI/MN titers were associated with modest protection from MMID in CHIM; leaves open their validation as reliable correlates for vaccine development.
Structured PICO
P
Population
76 healthy adults aged 18 to 49 years, without recent influenza vaccination, who underwent a controlled human infection with influenza A (H1N1)pdm09 and were followed for up to 91 days.
E
Exposure
Influenza A/Bethesda/MM2/H1N1 (an A/California/04/2009/H1N1pdm-like virus) challenge, administered as 1 mL of virus product in each nostril (total 1x10^7 TCID50).
O
Outcome
Mild-to-moderate influenza disease (MMID), defined as ≥1 post-challenge positive qualitative RT-PCR test with a qualifying symptom/clinical finding within 7 days post-challenge.composite
Main Result
Odds Ratio: 0.81 (95% CI 0.62–1.06)
Absolute Event Rate: 64.9% vs 76.9%
p-value: p=0.126
In a controlled human infection model, high baseline HAI and MN titers were associated with protection from mild-to-moderate influenza illness, though the primary odds ratio for HAI did not reach statistical significance.
Limitations
- Study was not designed to test any specific null hypothesis or reach a pre-determined level of estimation precision
Cite This Study
Ortiz et al. (2022) studied Influenza A (H1N1)pdm09 infection (n=76). Baseline hemagglutination inhibition (HAI) titer vs. Lower baseline HAI titer was evaluated on Mild-to-moderate influenza disease (MMID) (OR 0.81, 95% CI 0.62-1.06, p=0.126). Every two-fold increase in baseline hemagglutination inhibition titer was associated with a non-significant 19% decrease in the odds of developing mild-to-moderate influenza disease (OR 0.81).
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