Influenza Vaccine

Reinfection of Identical Influenza Virus May Not Be Rare

Not only is sequential infection with the identical influenza A virus possible, but it is also may not be rare, according to results of a new study.

“The data presented here raise questions that must be investigated further as they could impact the development of broadly protective or universal vaccines,” the researchers wrote.

To reach this conclusion, the researchers studied data on 7 individuals who participated in 2 independent viral challenge studies. Between 7.5 and 18.5 months after their participation in the first study, the individuals received the identical influenza A(H1N1)pdm09 virus intranasally.

Prechallenge and postchallenge hemagglutination inhibition, neuraminidase inhibition, and stalk antibody titers; peripheral blood leukocyte host gene expression response profiles; daily viral detection via nasal wash; and clinical signs and symptoms were all recorded from the sequential influenza challenge studies.

After approximately 1 year, at least 2 of the 7 participants were reinfected by the identical A(H1N1)pdm09 influenza virus, showing that previous infection experience did not provide sterilizing protective immunity.

Furthermore, evidence of sequential infection was laboratory-confirmed in at least 3 of the participants and was demonstrated via clinical evidence in 5 of the participants. According to the study authors, this data suggest that sequential infection is not a rare phenomenon.

These data raise questions about immune memory responses in an acute superficial respiratory mucosal infection and their implications in development of broadly protective influenza vaccines,” the researchers concluded. “Further investigation of these observations is warranted.”

—Colleen Murphy


Memoli MJ, Han A, Walters KA, et al. Influenza A reinfection in sequential human challenge: implications for protective immunity and “universal” vaccine development. Clin Infect Dis. 2020;70(5):748-753.