Profile of children's flu deaths details risks to healthy kids

A snapshot of all flu deaths that have been reported in children over eight recent flu seasons shows that a substantial number occurred in previously healthy kids and that the disease can kill quickly, sometimes within days and before hospitalization.

The analysis by a team from the US Centers for Disease Control and Prevention (CDC) appears to be the most comprehensive look so far into kids' flu deaths and appears today in Pediatrics.

Flu deaths in kids became a nationally reportable condition in October 2004, and today's study covers the 2004-05 through the 2011-12 seasons. Over that time the CDC logged 830 flu deaths in children younger than 18. As shown in the study's graph of flu deaths by months, the number sometimes varied greatly by season, with the largest spike during the 2009-10 pandemic months, and the lowest number during the 2011-12 season, when just 35 deaths were reported.

The focus of the study was also to compare the characteristics of fatal flu cases in kids with underlying health conditions, thought to put them at greater risk of complications, with those who didn't have medical conditions. When information was available, the authors also looked at the vaccination status of children who died and whether they received antiviral medication.

The team defined the flu season as Oct 1 through Sep 30, except for the 2009 H1N1 pandemic, which was defined as two time periods: Oct 1, 2008, to Aug 29, 2009, and Aug 30, 2009, through Sep 30, 2010.

During the study years, the CDC's Advisory Committee for Immunization Practices (ACIP) gradually expanded its age-group recommendations for kids who should be immunized against flu, and though vaccine coverage has grown, it is still well below the Healthy People 2010 goal of 70%.

The United States is one of a few countries with a recommendation that children be routinely vaccinated against flu. Doubts about the effectiveness of the vaccine have kept some countries from adopting the recommendation. 

The evidence for protection with the injectable vaccine has been inconsistent in children ages 2 to 17 years, though stronger protection has been shown for younger children, those ages 6 months to 7 years old. Despite questions about protection, most health officials agree that the flu vaccine is still the best tool for preventing the disease until better, more reliably protective vaccines are available.

43% had no at-risk conditions

According to the analysis, of 794 children with known medical histories, 43% didn't have conditions that put them at risk for flu complications, though a disproportionate number of flu deaths were seen in kids with underlying conditions such as asthma. For example, cerebral palsy affects less than 1% of US children, but the condition was reported in 10% of kids' flu deaths.

Of kids with high-risk conditions, 33% had neurologic disorders, and 12% had genetic or chromosomal disorders.

The review of medical charts revealed that previously healthy youngsters appeared to die more quickly than those who had underlying conditions—one-third died within 3 days of symptom onset. Pneumonia was the most frequent complication.

The authors wrote that it's not clear why previously healthy kids seem to die sooner and that a comparison of clinical courses could yield clues, such as possible immune dysregulation.

Previously healthy kids were also more likely to have bacterial co-infections, which might account for some of the differences, the team added.

Low vaccine, antiviral use

The team observed that few of the children who died were vaccinated against flu. Of 511 kids with known vaccination status, 84 (16%) had been fully immunized. During the 2009-10 pandemic months, 66 (3%) had been fully vaccinated with the monovalent vaccine, which was delayed and didn't arrive in time to blunt the worst of the autumn pandemic wave.

Regarding antiviral treatment, among kids whose treatment status was known during the 2010-11 and 2011-12 flu seasons, 56 (44%) received the drugs. Hospitalized kids were more likely to receive antiviral medication.

The CDC team noted that parents and even health providers often think healthy kids aren't at risk for serious flu infections, but the study findings underscore the risk, which they said is especially great in toddlers younger than 2 years.

The authors said that the findings show that any child can be at risk for flu-related death, regardless of underlying health status, and underscore the importance of the ACIP recommendations for flu vaccination, which extend to nearly all people ages 6 months and older.

Flu vaccination is the best tool for preventing the disease, and kids with high-risk conditions are important targets for immunization, the researchers wrote.

In a statement today on the study, the CDC said the study suggests poor adherence to its antiviral recommendations, with less than half receiving the drugs.

The findings serve as a reminder that kids with signs of severe or worsening infections and those who are hospitalized should receive empirical treatment with drugs such as oseltamivir (Tamiflu), according to the team. They added that kids younger than 2 years and those with high-risk conditions should receive antiviral treatment, regardless of disease severity.

Wong KK, Jain S, Blanton L, et al. Influenza-associated pediatric deaths in the United States, 2004-2012. Pediatrics 2013 Oct 28 [Abstract]

See also:

Oct 28 CDC statement on the study

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