Consecutive Infections With Influenza A and B Virus in Children During the 2014-2015 Seasonal Influenza Epidemic.

In a retrospective analysis of the test results for 647 patients with laboratory-confirmed influenza, we identified 13 children with influenza A virus infection who were subsequently infected with influenza B virus after a mean interval of 50 days. None of these children were considered immunodeficient or had an increased frequency of infections. Our data provide novel information in showing that consecutive infection with influenza A and B viruses can occur during a regular influenza season in immune-competent children and that a preceding influenza A virus infection may not provide cross-protection against influenza B virus infection.