Perspective from William T. Gerson, MD
October 19, 2012
3 min read

Flu vaccinations at school clinics cut infection rates, improved attendance

Perspective from William T. Gerson, MD
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SAN DIEGO — Influenza vaccination of approximately one-quarter of one Los Angeles school population resulted in decreased influenza rates and improved school attendance. Herd immunity for unvaccinated children may occur in schools with vaccination rates approaching 50%, according to research presented here during ID Week 2012.

Pia Pannaraj, MD, MPH 

Pia Pannaraj

Pia Pannaraj, MD, MPH, assistant professor of pediatrics at the University of Southern California and Children’s Hospital Los Angeles, and colleagues looked at influenza from a proactive perspective and assessed the effect of immunization programs in elementary schools in the Los Angeles area. They found that vaccination decreased the rate of influenza infection and increased rates of attendance.

“It’s the school-aged children who spread the flu. They generally are contagious even when active, so they tend to be around other children, giving it to them and spreading it for longer periods of time,” Pannaraj said in a press release. “It seems like the best place to prevent community spread of influenza is actually to go and prevent it at the school level.”

The investigators analyzed eight elementary campuses with similar socio-demographic characteristics. Half were tagged as control schools and the other half as the intervention sites. Together they enrolled nearly 4,500 students.

During the 2010-2011 academic year, between 27.8% and 47.3% of students in the intervention schools received at least one dose of influenza vaccine. Children who reported influenza-like symptoms were tested to confirm influenza diagnosis. More than 1,000 specimens obtained during a 15-week surveillance period showed that unvaccinated children in any school were 2.9 times more likely to get the influenza compared with unvaccinated children. The results also showed that influenza rates were higher overall in the control schools — 5.5 per 100 children compared with 3.9 in the schools where immunizations had been given.

Not surprisingly, rates of absenteeism were also higher in the control schools (4.2 vs. 3.9 days per 100 school days), and students with influenza missed more school days than their peers with other respiratory viruses.

The one school where almost 50% of students received influenza vaccine showed that the widespread coverage seemed to better protect the unvaccinated students, who were half as likely to get influenza as those in the control schools.

Pannaraj said the effect of widespread vaccination not only protects the child but a community because school-aged children can easily share the virus with classmates, teachers and others. But within a school, they can just as easily — and quite efficiently — be immunized.

“Schools are the best place for a campaign to prevent the spread of influenza,” she said.

David Kimberlin, MD, an ID Week chair for the Pediatric Infectious Diseases Society and a course director for the upcoming 25th Annual Infectious Diseases in Children Symposium, said the influenza studies illustrate why parents should pay attention to influenza and how they and their communities can work together during influenza season.

“The findings underscore how severe the flu can be, even for children with no predisposing risk factors, and why all families should try to protect themselves against the virus,” Kimberlin said. “School-based vaccination programs are a key strategy in that. The benefits are immediate and, if enough students get immunized, protection can extend to children not receiving vaccine. Public health officials will find these data very useful as they continue to work toward the goal of influenza control throughout the US population.”

IDWeek 2012 is the first joint meeting of the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, the Society for Healthcare Epidemiologists of America, and the HIV Medical Association.

For more information:

Pannaraj P. Abstract #1521. Presented at: ID Week 2012; Oct. 17-21, 2012; San Diego.

Disclosure: This study was supported by the Thrasher Foundation Early Career Award. Pannaraj and Kimberlin report no relevant financial disclosures.