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Table 2 Power for analysis of primary exposure-outcome associations

From: Impact of early life exposures to geohelminth infections on the development of vaccine immunity, allergic sensitization, and allergic inflammatory diseases in children living in tropical Ecuador: the ECUAVIDA birth cohort study

Primary exposures (geohelminth infections) Outcome Sample size available Analysis sample size Exposure prevalence Expected prevalence of outcomes
(exposed vs. unexposed groups)
Α Power
Maternal Vaccine antibodies @ 7 mths       
     Hib 2,300 1,000 50% 65% vs. 75% 0.01 80%
     Rotavirus 2,300 1,000 50% 40% vs. 60% 0.01 > 99%
Maternal Vaccine antibodies @ 2 yrs       
     TT 1,955 1,000 50% 85% vs. 95% 0.01 > 99%
     HBV 1,955 1,750 50% 80% vs. 85% 0.05 80%
     OPV type 3 1,955 500 50% 80% vs. 95% 0.01 > 99%
Infant Vaccine antibodies @ 5 yrs       
     TT 1,725 1,000 35% 60% vs. 80% 0.01 99%
     HBV 1,725 1,500 35% 70% vs. 80% 0.01 95%
     OPV type 3 1,725 1,000 35% 50% vs. 70% 0.01 > 99%
Maternal SPT @ 3 years 1,840 1,840 50% 15% vs. 25% 0.01 99%
Infant SPT @ 3 years 1,840 1,840 35% 15% vs. 25% 0.01 > 99%
Maternal Eczema @ 3 years 1,840 1,840 50% 25% vs. 35% 0.01 99%
Maternal Asthma @ 5 years 1,725 1,725 50% 17% vs. 23% # 0.05 86%
Infant Asthma @ 5 years 1,725 1,725 35% 17% vs. 23% # 0.05 83%
Infant Asthma @ 5 years 1,725 1,207 20% 25% vs. 15% # 0.01 93%
  1. Random samples of the study population will be selected for analysis of the protective levels of vaccine antibodies. Based on data from the cohort we estimate that 20% of children will have allergen skin test reactivity to any allergen at 5 years, that 30% of children will have at least one documented episode of eczema by 3 years of age and that 20% of children will have asthma at 5 years. Based on data from the cohort we estimate that ~50% of mothers are infected with any geohelminth parasite and ~30% of children will have at least one documented geohelminth infection during the first 2 years of life.
  2. #-expected effects of geohelminth infections on asthma prevalence using data from cross-sectional analyses in Ecuador [58] and Brazil [59].