Infants are at greater risk for flu because of their immature immune systems and the lack of an effective vaccine against infection. Photo by didesign021/Shutterstock

COLUMBIA, Mo., Jan. 20 (UPI) -- Among groups of people who cannot be given the flu vaccine -- infants younger than 6 months old do not receive the vaccine for the same reason they are at higher risk than most people -- their immune systems do not yet protect against infection.

Scientists at the University of Missouri designed a new version of the flu vaccine replacing the adjuvant aluminum hydroxide with protein lactoferrin, finding it worked to prevent infection.


Aluminum hydroxide is used in the vaccine to provoke an immune response, in this case irritating the vaccination site to attract white blood cells called neutrophils to the area. Without attracting the cells, the body cannot learn to fight off infection when exposed to pathogens.

Neutrophils naturally secrete lactoferrin, which is also found in mother's milk and protects infants from infection. Boosting the amount in the body, researchers thought, could suitably replace the aluminum hydroxide.

"Influenza vaccine works by stimulating a person's immune system to make antibodies that attack the flu virus," said Dr. Michael Sherman, a researcher in child health at the University of Missouri's School of Medicine, in a press release. "However, infants younger than six months do not make antibodies when given flu vaccine. This is because the immune systems of these very young babies do not respond to the adjuvant, or additive, within the vaccine that boosts the body's immune response when confronted with a virus."

Researchers working on the study, published in Biochemical and Biophysical Research Communications, gave groups of mice similar in age to human infants a vaccine containing either aluminum hydroxide or lactoferrin and then exposed them to a strain of the flu.

Lactoferrin appeared to work better than aluminum hydroxide, and also offered four to five times more protection from flu when compared to a group given the vaccine without any type of adjuvant.

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"Currently, the best protection for neonatal babies is to vaccinate the mother and all those who will have close contact with the infant," Sherman said. "Our recent study was meant to test the possibility of creating a safe and effective flu vaccine for very high-risk premature infants. Now that we have, we feel that the use of a natural protein would make immunization not only possible but more accepted."