There was a low level of protection against influenza
among US military personnel during the 2010-2011 season. However, compared with
live attenuated vaccine, higher protection was observed with the trivalent
inactivated vaccine, researchers from the Armed Forces Health Surveillance
They also found that although TIVs offered more
protection than LAVs, there was no protection for influenza A/H1N1 for either
Our study is important because we examined
influenza case data at the subtype level, Angie Eick-Cost, PhD, special
studies lead at the Armed Forces Health Surveillance Center, told Infectious
Disease News. The finding of varying protection by subtype is important
for U.S. vaccine policymakers to know because it can affect their decisions on
vaccine formulations and strain selections for next years influenza
For the study, data were obtained from the Defense
Medical Surveillance System. From Sept. 1, 2010 to April 30, 2011, there were
603 individuals who had laboratory-confirmed, influenza-associated illness. The
study also included two comparison groups: one group with test-negative,
non-influenza respiratory illnesses and one group of healthy controls.
Immunization data were also obtained.
When compared against the test-negative controls,
vaccine effectiveness was higher for the TIV: 53% (95% CI, 25 to 71) vs.
13% (95% CI, 77 to 27) for the LAV. When compared against the
healthy controls, the TIV also prevailed in vaccine effectiveness: 23% (95% CI,
1 to 42) vs. 11% (95% CI, 15 to 31) for the LAV.
A 58% vaccine effectiveness was observed (95% CI, 21 to
78) against influenza A/H3N2 and a 34% vaccine effectiveness (95% CI, 122
to 80) found for influenza B. The researchers found no protection against
influenza A/H1N1 for either of the vaccine types. The overall vaccine
effectiveness was 37% (95% CI, 10 to 64).
This study emphasizes the need to conduct yearly
assessments of influenza vaccine effectiveness, especially when the vaccine
components change and when novel influenza strains are circulating,
Eick-Cost said. It would be interesting to further investigate the
apparent lack of protection by the vaccine against the A/H1 pandemic influenza
strain through immunologic studies.
Eick-Cost AA. PLoS One. 2012;doi:
The researchers report no relevant financial