Key result
Female sex was associated with a higher likelihood of symptoms (mean, 0.96 vs 0.80; P=0.003) and a higher median number of symptoms (4 vs 3; P=0.011) compared to males after influenza challenge.
Why the study?
Preclinical and retrospective human studies suggest adult females have worse influenza outcomes than males, but prospective studies in humans are lacking.
Are there sex differences in symptoms and shedding following influenza A challenge in healthy volunteers?
Cohort (n=164)
Are there sex differences in symptoms and shedding following influenza A challenge in healthy volunteers?
Absolute Event Rate: 0.96% vs 0.8%
p-value: p=.003
In a human challenge study, females exhibited more symptoms than males following influenza A infection, potentially linked to differences in prechallenge NAI titers.
Sex differences in influenza symptoms may inform challenge study design; leaves open effects on shedding and transmission.
BACKGROUND: Preclinical animal studies and retrospective human studies suggest that adult females have worse outcomes from influenza than males. Prospective studies in humans are missing. METHODS: Data from 164 healthy volunteers who underwent influenza A/California/04/2009/H1N1 challenge were compiled to compare differences between sexes. Baseline characteristics, including hormone levels, hemagglutination inhibition (HAI) titers, neuraminidase inhibition (NAI) titers, and outcomes after challenge were compared. Linear and logistic regression models were built to determine significant predictor variables with respect to outcomes of interest. RESULTS: HAI titers were similar between the sexes, but NAI titers were higher in males than females at 4 weeks and 8 weeks postchallenge. Females were more likely to have symptoms (mean, 0.96 vs 0.80; P = .003) and to have a higher number of symptoms (median, 3 vs 4; P = .011) than males. Linear and logistic regression models showed that prechallenge NAI titers, but not HAI titers or sex hormone levels, were predictive of all shedding and symptom outcomes of interest. CONCLUSIONS: Females in our cohorts were more likely to be symptomatic and to have a higher number of symptoms than males. NAI titers predicted all outcomes of interest and may explain differential outcomes between the sexes.
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Giurgea et al. (2021) conducted a cohort in Influenza (n=164). Female sex vs. Male sex was evaluated on Likelihood of symptoms (p=.003). Female sex was associated with a higher likelihood of symptoms (mean, 0.96 vs 0.80; P=0.003) and a higher median number of symptoms (4 vs 3; P=0.011) compared to males after influenza challenge.
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