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Influenza virus infections in infants
W P Glezen1, L H Taber, A L Frank
1Influenza Research Center, Department of Microbiology and Immunology, Baylor College of Medicine, Houston, TX 77030, USA. wglezen@fluctr.micro.bcm.tmc.edu
Insights
Infants face a higher risk of influenza and serious complications after six months of age. Maternal influenza vaccination can boost infant immunity, supporting delayed active immunization.
Area of Science:
- Pediatrics
- Immunology
- Infectious Diseases
Background:
- Live attenuated cold recombinant vaccines are proposed for universal childhood immunization.
- Maternal influenza immunization is recommended to enhance infant antibody levels and delay active immunization needs.
- Understanding influenza risk in infants is crucial for determining optimal active immunization timing.
Purpose of the Study:
- To examine the risk of influenza virus infection during an infant's first year of life.
- To inform the ideal timing for initiating active immunization against influenza in children.
Main Methods:
- Infants were monitored weekly for influenza virus infection from birth to one year.
- Serum specimens were collected at four-month intervals to test for infection evidence.
Main Results:
- One-third of 209 infants contracted influenza within their first year, with most infections occurring in the second six months.
- Serious illnesses, including otitis media and lower respiratory tract infections, were concentrated in infants older than six months.
- Influenza infections were detected more frequently after six months of age (43 cases) compared to before (26 cases).
Conclusions:
- Increased maternal antibody titers from influenza immunization, coupled with lower infant risk in the first six months, support initiating active immunization after six months.
- The findings suggest that delaying active immunization until after six months of age is appropriate.
- Maternal immunization strategies can play a role in protecting infants during their first year.
Background:
Universal immunization of children with live attenuated cold recombinant vaccine has been proposed. The renewed recommendation for maternal immunization with influenza vaccine should increase the amount of antibody transmitted to the infant and postpone the need for active immunization. This study examines the risk of influenza during the first year of life to provide information about the time to initiate active immunization.
Methods:
Infants followed from birth to 1 year of age in the Houston Family Study were monitored weekly for influenza virus infection. Serum specimens were tested for evidence of infection at 4-month intervals.
Results:
One-third of 209 infants were infected during the first year; most of the infections occurred during the second 6 months of life. Only 26 of 69 infections were detected before 6 months of age compared with 43 afterward. More striking was the concentration of serious illnesses in the latter half of the first year; 8 of 9 otitis media episodes and 9 of 11 lower respiratory tract illnesses occurred in the older infants.
Conclusions:
The combination of increased maternal antibody titers that should result from influenza immunization and the lesser risk of influenza in the first 6 months of life allows initiation of active immunization of children after 6 months of age.