Live-attenuated influenza vaccine was not as effective as inactivated vaccine at protecting children and adolescents against the influenza A(H1N1)pdm09 strain; however, the two vaccines were equally effective against influenza A(H3N2) and B strains, according to data in Pediatrics.
“In this study, we expand on previous analyses by evaluating vaccine effectiveness and relative effectiveness of [live-attenuated influenza vaccine (LAIV)] and [inactivated influenza vaccine (IIV)] by season and influenza type and subtype among children and adolescents aged 2 to 17 years from 2010-2011 through 2013-2014,” Jessie R. Chung, MPH, of the influenza division at the CDC, and colleagues wrote. “We found that lower LAIV effectiveness in 2013-2014 was specific to the A(H1N1)pdm09 vaccine component and was consistent with a previously unexamined effect during the 2010-2011 influenza season.”
The researchers studied influenza data for 6,819 children aged 2 to 17 years from the U.S. Influenza Vaccine Effectiveness Network for the 2010-2011, 2011-2012, 2012-2013 and 2013-2014 influenza seasons. Patient influenza-associated illness data were analyzed to compare the effectiveness of LAIV vs. IIV.
Study results showed that 2,066 study participants were vaccinated with IIV, while 637 were vaccinated with LAIV. During the 2013-2014 season, risk for influenza was significantly greater for children vaccinated with LAIV compared with children, particularly those aged 2 to 8 years, vaccinated with IIV (OR = 5.36; 95% CI, 2.37-12.13). Overall risks, however, were similar for LAIV and IIV during the other three seasons.
Chung and colleagues wrote that children vaccinated with LAIV had increased risk for illness caused by influenza A(H1N1)pdm09 during the 2010-2011 and 2013-2014 seasons. They also said those vaccinated with LAIV or IIV had similar risks associated with influenza A(H3N2) and B strains.
“It will be important to monitor influenza type- and subtype-specific relative effectiveness in the future as vaccination uptake increases and vaccine composition changes or new vaccines are introduced,” Chung and colleagues wrote. “Influenza vaccine effectiveness can vary with changes in vaccine components or circulating influenza viruses and requires ongoing evaluation to inform vaccine recommendations.” – by David Costill
Disclosure: Chung reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.