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Table 2 Summary of studies reporting reporting incidence of influenza virus infection using serology

From: Incidence of influenza virus infection among pregnant women: a systematic review

Study Number of cases Denominator Crude incidence rate (CI)
(aor derived from %)
95% CI Pandemic or seasonal? Study design Grading system and scoreb Hospital-basSummary of studies reporting repored or clinic-based? Duration of surveillance (months or years) Country
Griffiths 1980 77 1,595 483 per 10,000 pregnanciesa (399–614) Seasonal Cohort NOS = 7 Hospital 3 years (22 months total influenza season) UK
Hardy 1961 61 671 909 per 10,000 pregnanciesa (716–1,155) Pandemic Cohort NOS = 6 Clinic 5 months US
Irving 2000 182 1,659 1,097 per 10,000 pregnanciesa (957–1,258) Seasonal Cohort NOS = 7 Hospital 15 months UK
  1. aCalculated from provided number of cases or %
  2. b NOS Newcastle-Ottawa Scale