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Comment & Response
October 2017

Influenza A Infections in Infants of Vaccinated and Unvaccinated Mothers—Reply

Author Affiliations
  • 1Department of Epidemiology Research, Statens Serum Institut, Copenhagen S, Denmark
JAMA Pediatr. 2017;171(10):1015. doi:10.1001/jamapediatrics.2017.2394

In Reply We thank Sandy et al for the interest in our article1 and for the pertinent question. The data on influenza A infections (defined by hospitalizations with International Statistical Classification of Diseases and Related Health Problems, Tenth Revision code J09) are sparse in our cohort. Only 1 case was observed in children of mothers vaccinated in the first trimester and none in children of the propensity score–matched unvaccinated mothers. We observed 2 cases in children of mothers vaccinated in the second or third trimester and 22 in children of the propensity score–matched unvaccinated mothers, yielding a rate ratio of 0.34 (95% CI, 0.08-1.43). For other types of influenza infections and unspecified influenza infections (defined by hospitalizations with International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes J10 and J11), we observed 2 cases in children of mothers vaccinated in the first trimester and none in children of the propensity score–matched unvaccinated mothers. We observed 14 cases in children of mothers vaccinated in the second or third trimester and 53 in children of the propensity-score matched unvaccinated mothers, yielding a rate ratio of 0.98 (95% CI, 0.54-1.77). In conclusion, these results do indicate a protective effect on influenza A in offspring of the vaccinated mothers, but the statistical power is unfortunately low.

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