Influenza vaccine nasal spray more effective in young children

August 25, 2011

With influenza being one of the most common reasons for hospitalization of children, finding the most effective vaccination combination is increasingly important. That?s what researchers recently set out to do, finding that although the live attenuated influenza vaccine nasal spray and trivalent inactivated influenza vaccine shots are effective, only the nasal spray may confer additional immunity. Could a change in guidelines be on the horizon?

Both live attenuated influenza vaccine (LAIV) nasal spray and trivalent inactivated influenza vaccine (TIV) shots protect children aged 6 months to 3 years from influenza and produced similar levels of antibodies, but a recent study found that only the nasal spray induces production of 3 T-cell subtypes that may confer additional immunity.

Vaccination is increasingly critical, because influenza is now 1 of the top 10 reasons for hospitalization of children younger than 17 years, accounting for nearly 40,000 hospitalizations in 2009, reports the Agency for Healthcare Research and Quality. Children younger than 2 years are most likely to suffer severe complications from the flu, and children younger than 5 years make up about half of the total hospitalizations for influenza, according to new data from the Centers for Disease Control and Prevention (CDC).

Children younger than 3 years receive 2 doses of flu vaccine-a priming dose followed a month later by a booster. Researchers at the National Institutes of Health tested whether matching the 2 doses was better than giving 2 different types of vaccine. The 2 doses were given as matching (both TIV or both LAIV) or mixed (TIV followed by LAIV or LAIV followed by TIV). Researchers found that all 4 combinations were safe and effective.

The young children who received at least 1 dose of LAIV, however, also produced 3 types of influenza-specific T cells. There was no significant difference in T-cell production between those who received 1 or 2 doses of LAIV, and the order in which LAIV was administered also had no effect.

The testing involved 53 children aged 6 to 35 months during the 2005-2006 and 2006-2007 flu seasons.

The American Academy of Pediatricians (AAP) recommends that toddlers who have not previously had a flu vaccine or who received just 1 dose in the previous year receive a priming dose followed a month later by a booster. The AAP and CDC recommend using TIV for children younger than 2 years; LAIV is not licensed for this age group.

Because LAIV has been associated with increased wheezing in very young children, lead study researcher Daniel F. Hoft, PhD, suggests that children younger than 2 years may do best if they receive the TIV shot first, followed by the LAIV spray. He notes that additional research is needed to evaluate the safety and efficacy of this regimen, which does not follow current protocols.

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