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Influenza A virus may not cross-protect children against influenza B
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Recent findings published in The Journal of Infectious Diseases showed that nonvaccinated children could be consecutively infected with influenza A virus then influenza B, suggesting that influenza A may not provide cross-protection against influenza B.
“To our best knowledge, this is the first description of subsequent infection with influenza A and B virus in immunocompetent children during an influenza season,” Johannes Möst, MD, of the microbiology diagnostic laboratory at the Medical University of Innsbruck, Austria, and his colleague wrote. “Interestingly, we found subsequent infections only in children. This could be because there is a certain degree of protection in adults due to vaccinations and infections in previous years or because adults who experienced influenza-like symptoms several weeks after the initial influenza A virus infection was diagnosed were less likely than children to consult a physician again.”
During a typical influenza season in Austria, circulating viruses consist of two or three influenza A viruses and one influenza B virus. No information, however, existed about whether a patient infected with one type of virus could experience a second virus type within the same season.
In this retrospective case analysis, the researchers assessed 647 patients with laboratory-confirmed influenza. The investigators determined influenza A in 374 children, influenza B in 271 children, and coinfection in two children. In addition, they observed that 33 children previously infected with influenza A virus had again presented with clinical symptoms of influenza after a mean duration of 50 days. None of these patients had influenza A virus, but 13 had influenza B virus. After creating a calendar, the researchers found that influenza A predominated from December to February, while B predominated in March and April.
These results suggested that influenza A virus may not cross-protect against influenza B, the researchers wrote.
“This would be predictable from the different antigenic profiles of influenza A and B viruses, but to our best knowledge this has not been prospectively studied in humans,” the researchers wrote. “Physicians should take the diagnosis of influenza in subjects presenting with influenza-like illness into consideration even if these patients received the diagnosis of influenza previously during the same epidemic season.” – by Will Offit
Disclosure: The researchers report no relevant financial disclosures.
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