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Study Looks at Flu Vaccine Dosing in Children

Children who got 2 doses as recommended had higher vaccine effectiveness

A study in the Pediatric Infectious Disease Journal underscores the value of a child getting two doses of vaccine the first season they are vaccinated and indicates that flu vaccination can provide residual immunity in children during subsequent seasons. CDC recommends that children aged 6 months through 8 years of age get two doses of flu vaccine, at least one month apart, the first year they are vaccinated against flu. The first dose “primes” the immune system; the second dose provides immune protection. The study found that children 2 years to 8 years of age who got the recommended first-time two doses of flu vaccine during a prior season had higher flu vaccine effectiveness (VE) than those who had not.

The study looked at vaccination history and vaccine effectiveness data on patients 6 months to 8 years of age from clinics in five states that are part of the U.S. Flu VE Network during the 2011-2012 and 2012-2013 to find trends. Higher VE point estimates were observed among children 2 years through 8 years of age who had gotten two doses of vaccine during a prior season compared to those who had not against A (H3N2) and B influenza illnesses separately. In fact, children who had not gotten 2 doses of vaccine during a prior season were about twice as likely (2. 4-fold) to be sick with influenza A (H3N2) than children who got 2 doses during a prior season.

Other results further underscore the value of flu vaccine in children in the form of residual or long-term immunity following vaccination. Children who were vaccinated during the previous season but who but missed flu vaccination in the study season appeared to benefit from residual protection from flu vaccine. VE point estimates of about 40% were observed among previously vaccinated children aged 2 years through 8 years who had missed vaccination during the study seasons. This was noted during both the first study season (2011-2012) when the prior year vaccine components had not changed, as well as during the second study year (2012-2013) when the influenza A (H3N2) and influenza B components had changed.

These findings support the current CDC and ACIP recommendations for two doses of flu vaccine in vaccine naive young children. The study also reinforces the importance of examining influenza VE among children within the context of prior vaccination history and priming.

Children younger than 5 years of age – especially those younger than 2 years old – are at high risk of serious flu complications. It is estimated that more than 20,000 children younger than 5 years old are hospitalized due to flu complications each year in the United States. CDC recommends that everyone 6 months and older get a yearly flu vaccine to reduce the risk of flu illness and its potentially serious complications. Children of any age with certain chronic health conditions, including asthma, diabetes, a weakened immune system for any reason and neurological or neurodevelopmental disorders are at higher risk of experiencing severe outcomes from flu infection.

Flu activity is low in the United States at this time, but there are early indications that activity is beginning to pick up. More than 130 million doses of 2015-2016 flu vaccine have been distributed so far in the United States this season. While how well the vaccine works can vary, flu vaccine is the best way to protect against flu. It takes about two weeks after vaccination for protection to set in, making now the perfect time to get vaccinated.

Recommendations on the control and prevention of influenza are published annually. Existing recommendations are available at Seasonal Influenza Vaccination Resources for Health Professionals. Updated recommendations for the 2015-2016 season are available on the CDC website.

For more information about children and flu, visit Children, the Flu, and the Flu Vaccine

The study is available online in the Pediatric Infectious Disease Journal