711. Comparison of Influenza Vaccine Effectiveness Estimates Using Data from the Influenza Incidence Surveillance Project and the US Influenza Vaccine Effectiveness Network, 2011–12 through 2014–15.
Session: Poster Abstract Session: Vaccines
Thursday, October 27, 2016
Room: Poster Hall
Background: The US Influenza Vaccine Effectiveness Network (Flu VE) conducts research to provide annual assessments of influenza VE among ambulatory patients with acute respiratory infection (ARI). The Influenza Incidence Surveillance (IISP), a lower cost public health surveillance system, monitors laboratory-confirmed influenza among ambulatory patients with influenza-like illness. We compared estimated VE using data from the two platforms.

Methods: We included outpatients with ARI aged ≥6 months who enrolled in Flu VE or IISP ≤7 days after illness onset during influenza seasons from 2011–12 to 2014–15. Influenza status was determined by RT-PCR. VE was estimated as (1-adjusted odds ratio) x 100% for vaccination among influenza cases vs. influenza test-negative controls from logistic regression models including age, geographic region, and calendar time; high-risk conditions were not included because they were not captured in IISP. Self-reported vaccination was defined as receipt of ≥1 dose of vaccine at least 14 days before illness onset.


Among 26,577 Flu VE subjects, 25% tested positive for influenza and 55% reported being vaccinated. Among 11,286 IISP subjects, 33% tested positive for an influenza virus and 31% reported being vaccinated. VE estimates against A(H3N2) virus were 30% (95% confidence interval (CI): 25–36) in Flu VE and 36% (95% CI: 27–44) in IISP. Against A(H1N1)pdm09 virus, VE estimates were 64% (95% CI: 59–69) in Flu VE and 62% (95% CI: 51–71) in IISP. Against any influenza B virus, VE estimates were 61% (95% CI: 56–65) in Flu VE and 55% (95% CI: 46–62) in IISP. Adjusted VE estimates against any influenza were comparable for both platforms for all seasons (Table).

Table. Adjusted vaccine effectiveness (VE) against any influenza

Adjusted VE (95% CI)


Flu VE



55 (46–62)

48 (31–60)


51 (45–56)

48 (31–55)


58 (52–64)

53 (39–63)


27 (18–34)

30 (15–43)

Conclusion: VE estimates from two platforms that included the same variables were similar. While estimates from Flu VE were more precise due to a larger sample size, data from IISP could contribute additional numbers and geographic representation to an evaluation of VE during pandemics. This could be facilitated by improving the collection of vaccination status and potential confounders in IISP.

Jessie Chung, MPH1, Ashley Fowlkes, MPH2, Mark G. Thompson, PhD3, Andrea Steffens, MPH2, Sarah Spencer, PhD2, Swathi Thaker, PhD3, Alicia M. Fry, MD, MPH2 and Brendan Flannery, PhD2, (1)Atlanta Research and Education Foundation, Inc, Atlanta, GA, (2)Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, (3)Centers for Disease Control and Prevention, Atlanta, GA


J. Chung, None

A. Fowlkes, None

M. G. Thompson, None

A. Steffens, None

S. Spencer, None

S. Thaker, None

A. M. Fry, None

B. Flannery, None

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