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ISDS Annual Conference Proceedings 2012. This is an Open Access article distributed under the terms of the Creative Commons Attribution-
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ISDS 2012 Conference Abstracts

Effectiveness of the 2011-12 Influenza Vaccine: Data
from US Military Dependents and US-Mexico Border
Civilians
Damaris Padin*, Anthony Hawksworth, Peter Kammerer, Erin McDonough and Gary Brice

Operational Infectious Diseases, Naval Health Research Center, San Diego, CA, USA

Objective
To assess effectiveness of the influenza vaccine among US military

dependents and US-Mexico Border populations during the 2011-12
influenza season.

Introduction
As a result of antigenic drift of the influenza viruses, the compo-

sition of the influenza vaccine is updated yearly to match circulating
strains. Consequently, there is need to assess the effectiveness of the
influenza vaccine (VE) on a yearly basis. Ongoing febrile respiratory
illness (FRI) surveillance captures data and specimens that are lever-
aged to estimate influenza VE on an annual basis.

Methods
Data from ongoing FRI surveillance at US Military and US-Mex-

ico border clinics were used to estimate VE. We conducted a case–
control study between weeks 3 and 17 of the 2011-12 influenza
season. Specimens were collected from individuals meeting FRI case
definition (fever ! 100.0 F with either cough or sore throat). Cases
were laboratory confirmed influenza infection and controls were neg-
ative for influenza. Interviewer-administered questionnaires collected
information on patient demographics and clinical factors and vacci-
nation status. Logistic regression was used to calculate the crude and
adjusted odds ratios (OR) and VE was computed as (1-OR) x 100%.
Vaccine protection was assumed to begin 14 days post-vaccination.

Results
A total of 155 influenza positive cases and 429 influenza negative

controls were included in the analysis - 72 cases were influenza
A(H3N2), 38 cases were influenza A(H1N1), and 45 cases were in-
fluenza B. Overall adjusted VE against laboratory-confirmed in-
fluenza was 46% (95% CI, 19–64%); unadjusted was 39% (95% CI,
11–58%). Influenza subtype analyses revealed moderate protection
against A/H3 and A/H1 and lower protection against B. Lowest esti-
mated VE was seen in older individuals, age 65 and older.

Conclusions
Influenza vaccination was moderately protective against labora-

tory confirmed influenza in this population. Continued surveillance
is important in monitoring the effectiveness of the influenza vaccine.

Keywords
Influenza; vaccine efficacy; Influenza-like illness surveillance

Acknowledgments

The authors gratefully acknowledge the work of on-site research assis-
tants and NHRC laboratory staff who produced the data used in this analy-
sis. We also thank Global Emerging Infections System (GEIS) division of
the Armed Forces Health Surveillance Center (AFHSC) for their support
of FRI surveillance.

*Damaris Padin
E-mail: damaris.padin@med.navy.mil

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 5(1):e5, 2013