Back to Top Skip to main content Skip to sub-navigation

Brief Report: Department of Defense Midseason Estimates of Vaccine Effectiveness for the 2018–2019 Influenza Season

Adminstration of a seasonal flu vaccination. (U.S. Navy photo) Adminstration of a seasonal flu vaccination. (U.S. Navy photo)

Recommended Content:

Medical Surveillance Monthly Report

BACKGROUND

Military populations have historically been at high risk for acute respiratory infections, particularly training and deployed populations, who have living conditions that are often crowded and may be austere.1 Respiratory infections are responsible for over 300,000 medical encounters each year among U.S. active component service members, and the associated health care creates a substantial public health and economic burden on the Military Health System (MHS).1,2 Respiratory infections also account for approximately one-third of convalescence in quarters determinations and as such are a significant contributor to lost duty days.3 Viral respiratory pathogens are highly transmissible, and the specific types, trends, and risks often vary regionally and by setting.1 These variations are important for a globally dispersed force, as they inform risk assessments and ensure that proper preventive measures are implemented. Thus, the Department of Defense (DoD) conducts surveillance for respiratory infections both within the force and in other global populations. The Armed Forces Health Surveillance Branch’s (AFHSB) Global Emerging Infections Surveillance (GEIS) section supports a global surveillance program, executed primarily by DoD service laboratories, at approximately 400 locations in over 30 countries. Respiratory infection surveillance data are regularly shared with the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC). Because of frequent genetic mutations and the associated pandemic potential, influenza is of particular interest to the DoD and is a major focus of these surveillance efforts. Because influenza vaccination is the primary preventive countermeasure, the seasonal influenza vaccine’s effectiveness is also closely monitored. Estimates of vaccine effectiveness (VE) are calculated twice annually: during the middle and at the end of the influenza season.

METHODS

Three sites produced VE estimates for the DoD at midseason. The U.S. Air Force School of Aerospace Medicine/AFHSB-Air Force (USAFSAM/AFHSBAF) satellite VE estimate was produced from sentinel site surveillance within non-active component MHS beneficiaries (retirees and family members) receiving care at military treatment facilities (MTFs). The Naval Health Research Center (NHRC) VE estimate was derived from sentinel site influenza surveillance within civilian populations at clinics near the U.S.–Mexico border and among MHS beneficiaries (service members, retirees, and family members) receiving care at MTFs. The AFHSB’s Epidemiology and Analysis (E&A) section VE estimate was derived from electronic health record (EHR) data from active component service members receiving care at MTFs.

For the 2018–2019 midseason, all 3 VE estimates were calculated using a test-negative case-control study design; crude and adjusted VE estimates, along with 95% confidence intervals (CIs), were calculated as (1 - odds ratio) x 100% and were obtained from multivariable logistic regression models. VE results were considered statistically significant if 95% CIs around VE estimates did not include zero.

USAFSAM/AFHSB-AF satellite’s analysis adjusted for age group, time of specimen collection, region, and sex. NHRC’s analysis adjusted for age group. AFHSB E&A’s analysis adjusted for age group, month of diagnosis, 5-year vaccination status as a dichotomous variable, and sex. Analyses were performed for influenza types and subtypes as available. Cases were laboratory confirmed as influenza positive, and controls were influenza test negative. At NHRC and USAFSAM/AFHSB-AF satellite, influenza positives were confirmed through reverse transcription polymerase chain reaction (RT-PCR) and/or viral culture. AFHSB also used these methods for confirmation and included positive rapid tests, but individuals with only a negative rapid test, without another confirmatory test result were excluded from calculation of VE. USAFSAM/AFHSB-AF satellite verified vaccination status through EHR and self-report data, E&A verified vaccination status through EHR data, and NHRC used self-reported vaccination data. Nearly all vaccinated active duty and beneficiary patients received the inactivated influenza vaccine.

RESULTS

Non-active component MHS beneficiary data were collected from 9 December 2018 through 16 February 2019. The analysis was restricted to this time period to provide a more accurate VE estimate, as earlier months of the influenza season are control-heavy. By the end of the surveillance period, 48% of 645 cases and 64% of 1,446 controls had been vaccinated (Table). Non-active component MHS beneficiary cases tended to be younger than controls. U.S.–Mexico border population civilian and MHS beneficiary data were collected from 30 September 2018 through 15 February 2019, during which time 13% of 251 cases and 27% of 1,185 controls were vaccinated. Border population and MHS beneficiary cases tended to be younger than controls. Active component service member data were collected from 1 December 2018 through 16 February 2019, and 92% of 1,594 cases and 91% of 2,548 controls were vaccinated. In the active component service member group, controls tended to be younger than cases.

As shown in the Table and Figure, adjusted VE for all influenza types for non-active component MHS beneficiaries was 47% (95% CI: 35–57), indicating moderate protection against influenza infection. For active component service members, adjusted VE for all influenza types was low, at 13% (95% CI: -11–32). For all influenza A, adjusted VE for non-active component MHS beneficiaries was 48% (95% CI: 36–58), VE for U.S.–Mexico border population civilians and MHS beneficiaries was 58% (95% CI: 38–72), and VE for active component service members was 12% (95% CI: -13–31). For influenza A(H1N1), adjusted VE for non-active component MHS beneficiaries was 57% (95% CI: 44–68), VE for U.S.–Mexico border population civilians and MHS beneficiaries was 65% (95% CI: 46–77), and VE for active component service members was 34% (95% CI: -19–64). Influenza A(H3N2) was not detected in high enough proportions in most populations to calculate VE, but for non-active component MHS beneficiaries, adjusted VE was 36% (95% CI: 14–53), indicating low-to-moderate protection. Similarly, influenza B was not detected in high enough proportions in most populations early in the 2018–2019 season to calculate VE; however, for active component service members, adjusted VE was 25% (95% CI: -8–48), indicating low protection.

EDITORIAL COMMENT

The DoD laboratories and partners conducting respiratory infection surveillance provide a valuable global perspective and capability. Monitoring global trends, particularly for influenza, provides situational awareness for DoD leaders and informs current and future operation risk assessments and recommendations for preventive measures. This surveillance also facilitates sample sharing and further collaboration with WHO and CDC.

In general, for civilian populations, influenza vaccination provided moderate protection against infection, and DoD-generated VE estimates of non-service member beneficiaries and select civilian populations were similar to CDC estimates for the same time frame. CDC reported that adjusted VE for all influenza types was 47%, adjusted VE for influenza A(H1N1) was 46%, and adjusted VE for influenza A(H3N2) was 44%.4 In CDC and DoD analyses, protection was greater for influenza A(H1N1) than influenza A(H3N2). However, for active component service members, adjusted VE estimates were much lower, though not statistically significant. This difference may be partially attributable to the requirement for annual influenza vaccination and the resulting high proportion of vaccination in this population. The effect is demonstrated by the case and control populations having nearly identical vaccination rates. The high vaccination rate makes it difficult to design a strong epidemiological study of VE in this population. Other factors, such as the requirement for service members to receive the vaccination annually, which may have biological effects such as attenuated immune response due to repeated exposures, may also impact the VE estimates. The timing of vaccination could also impact the VE estimates since service members typically receive the vaccine early in the influenza season or just before it starts. These factors should also be considered as potential contributors to the low VE estimates for the active component service members.

One important limitation of this study is potential non-differential misclassification of vaccination status due to poor recall on the self-reported questionnaire or documentation errors in the EHR. Also, the analyses did not assess vaccine impact on less severe cases of influenza since the VE estimates only include medically attended patients, and the populations studied are younger than the U.S. general population, which may reduce generalizability. More work, potentially using new methodologies, is needed to accurately estimate the vaccine’s effect on reducing the influenza burden in active component service members and to determine the impact of repeat vaccinations on immune response to the vaccine or subsequent influenza exposures. Additional data and analyses in these areas would fill knowledge gaps and inform a more robust military influenza vaccination policy.

 

Author affiliations: Defense Health Agency, Armed Forces Health Surveillance Branch, Silver Spring, MD (Ms. Lynch, CDR Scheckelhoff, Dr. Eick-Cost, Ms. Hu, Ms. Johnson); General Dynamics Information Technology, Fairfax, VA (Ms. Lynch, Ms. Johnson); Defense Health Agency, Armed Forces Health Surveillance Branch-Air Force satellite, U.S. Air Force School of Aerospace Medicine, Wright-Patterson Air Force Base, OH (Mr. Coleman, Ms. DeMarcus, Lt Col Federinko); STS Systems Integration, LLC, San Antonio, TX (Mr. Coleman, Ms. DeMarcus); Cherokee Nation Technologies, Tulsa, OK (Dr. Eick-Cost, Ms. Hu); Naval Health Research Center, San Diego, CA (Mr.Hansen, LCDR Graf, Dr. Myers); Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD (Mr. Hansen)

Acknowledgments: The authors thank the Department of Defense Global Respiratory Pathogen Surveillance Program and its sentinel site partners, the Navy and Marine Corps Public Health Center, and the Centers for Disease Control and Prevention’s Binational Border Infectious Disease Surveillance Program in San Diego and Imperial Counties, CA, which collected samples and case data from participating outpatient clinics.

Disclaimer: Authors include military service members or employees of the U.S. Government. This work was prepared as part of their official duties. Title 17, U.S.C. §105 provides that copyright protection under this title is not available for any work of the U.S. Government. Title 17, U.S.C. §101 defines a U.S. Government work as work prepared by a military service member or employee of the U.S. Government as part of that person’s official duties.

Report No. 19-39 was supported by the Armed Forces Health Surveillance Branch’s Global Emerging Infections Surveillance section under work unit no. 60805. The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of the Air Force, Department of Defense, or the U.S. Government.

The study protocol was approved by the Naval Health Research Center Institutional Review Board in compliance with all applicable Federal regulations governing the protection of human subjects. Research data were derived from an approved Naval Health Research Center Institutional Review Board protocol number NHRC.2007.0024.

 

REFERENCES

1. Sanchez JL, Cooper MJ, Myers CA, et al. Respiratory infections in the U.S. military: recent experience and control. Clin Microbiol Rev. 2015;28(3):743–800.

2. Armed Forces Health Surveillance Branch. Absolute and relative morbidity burdens attributable to various illnesses and injuries, active component, U.S. Armed Forces, 2018. MSMR. 2019;26(5):2–10.

3. Armed Forces Health Surveillance Branch. Ambulatory visits, active component, U.S. Armed Forces, 2018. MSMR. 2019;26(5):19–25.

4. Doyle JD, Chung JR, Kim SS, et al. Interim estimates of 2018–19 seasonal influenza vaccine effectiveness–United States, February 2019. MMWR Morb Mortal Wkly Rep. 2019;68(6)135–139.

 

DoD midseason influenza VE estimates, 2018–2019

DoD midseason influenza VE, 2018–2019

You also may be interested in...

Brief Report: The Challenge of Interpreting Repeated Positive Tests for SARS-CoV-2 Among Military Service Members, Fort Jackson, SC, 2020–2021

Article
10/1/2021
An example of a negative rapid test for the SARS-CoV-2 virus (COVID-19). The Texas Military Department has begun distributing rapid COVID-19 tests to its service members across the state as a force health protection measure. This will ensure that the Soldiers and Airmen serving their communities during the COVID-19 pandemic remain healthy and safe. (Photo by ENS Charles E. Spirtos)

Recommended Content:

Medical Surveillance Monthly Report

Surveillance Snapshot: History of COVID-19 Vaccination Among Air Force Recruits Arriving at Basic Training, March 2–June 15, 2021

Article
10/1/2021
COVID-19 vaccine bottle and syringes

Recommended Content:

Medical Surveillance Monthly Report

Update: Cold Weather Injuries, Active and Reserve Components, U.S. Armed Forces, July 2016–June 2020

Article
10/1/2021
A student participates in a cold-water immersion training at Fort McCoy, Wis., Jan. 17, 2020, as a part of the Cold-Weather Operations Course. (Photo By Scott Sturkol, Army)

Recommended Content:

Medical Surveillance Monthly Report

Surveillance Snapshot: Influenza Immunization Among U.S. Armed Forces Health Care Workers, August 2016–April 2021

Article
10/1/2021
Staff Sgt. James H. Wagner, William Beaumont Army Medical Center, vaccinates Maj. Gen. M. Ted Wong, commanding general, William Beaumont Army Medical Center, with the seasonal flu vaccines. All WBAMC beneficiaries are encouraged to get vaccinated against the seasonal flu vaccine and the novel flu virus. Look for flu updates on the WBAMC Facebook page, the All Bliss and the Fort Bliss Monitor. (Photo by SGT Valerie Lopez)

Recommended Content:

Medical Surveillance Monthly Report

Update: Routine Screening for Antibodies to Human Immunodeficiency Virus, Civilian Applicants for U.S. Military Service and U.S. Armed Forces, Active and Reserve Components, January 2016–June 2021

Article
9/1/2021
HIV awareness graphic is created on Adobe Photoshop at Fort Carson, Colorado, July 16, 2021. Measures taken to reduce the risk of contracting HIV is abstinence, using condoms while having sex, taking preventative medications, getting tested for HIV or other STDs regularly, and talking to your sexual partners about HIV and STDs. (U.S. Army graphic by Spc. Woodlyne Escarne)

Recommended Content:

Medical Surveillance Monthly Report

Is Suicide a Social Phenomenon during the COVID-19 Pandemic? Differences by Birth Cohort on Suicide Among Active Component Army Soldiers, Jan.1, 2000–June 4, 2021

Article
9/1/2021
Spc. Brittney VerBerkmoes speaks among fellow Soldiers in a group centered on finding a way for the Army to mitigate the amount of suicides that occurs among Soldiers. The Solarium was held to help junior service members to communicate with the Army’s senior leaders about finding solutions to important issues occurring in the Army. (U.S. Army photo by Sgt. Elizabeth Rundell)

Is Suicide a Social Phenomenon during the COVID-19 Pandemic? Differences by Birth Cohort on Suicide Among Active Component Army Soldiers, 1 January 2000–4 June 2021

Recommended Content:

Medical Surveillance Monthly Report

Surveillance Snapshot: A Simple Model Estimating the Impact of COVID-19 on Lost Duty Days Among U.S. Service Members

Article
9/1/2021
U.S. Navy Hospital Corpsman 2nd Class Julian Gordon, left, a preventative medicine technician with Marine Rotational Force - Darwin, administers a COVID-19 test to a U.S. Marine with MRF-D, at Royal Australian Air Force Base, Darwin, NT, Australia, March 22, 2021. Marines and Sailors with MRF-D are required to conduct strict COVID-19 mitigation procedures prior to arrival in Darwin, in compliance with Northern Territory Health Authorities. All service members must provide three documented negative COVID-19 swab tests throughout their travel and prior to being released from a 14-day quarantine period. (U.S. Marine Corps photo by Sgt. Micha Pierce)

Recommended Content:

Medical Surveillance Monthly Report

Brief Report: Relationships between Self-reported Psychological Conditions and Aggressive Behaviors Among Crew Members of a U.S. Navy Aircraft Carrier, January 2021

Article
9/1/2021
A U.S. Marine Corps drill instructor with Golf Company, 2nd Recruit Training Battalion, motivates a recruit during a Marine Corps Martial Arts Program (MCMAP) training session at Marine Corps Recruit Depot, San Diego, Aug. 2, 2021. The drill instructors ensured recruits conducted the techniques safely and effectively during the training session. (U.S. Marine Corps photo by Cpl. Zachary T. Beatty)

Recommended Content:

Medical Surveillance Monthly Report

Cross-Sectional Analysis of the Association between Perceived Barriers to Behavioral Health Care and Intentions to Leave the U.S. Army

Article
9/1/2021
U.S. Army Central Reserve component Soldiers swear the oath of enlistment during a mass reenlistment ceremony in celebration of the U.S. Army Reserve 113th birthday at Camp Arifjan, Kuwait, April 23, 2021. This ceremony reaffirms their commitment to the U.S. Army Reserve and the people of the United States. (U.S. Army photo by Sgt. Robert Torres, 203rd Public Affairs Detachment)

Recommended Content:

Medical Surveillance Monthly Report

Mental Health Disorders, Behavioral Health Problems, Fatigue and Sleep Outcomes in Remotely Piloted Aircraft/Manned Aircraft Pilots, and Remotely Piloted Aircraft Crew, U.S. Air Force, 1 October 2003–30 June 2019

Article
8/1/2021
U.S. Air Force Capt. Danielle ‘Dani’ Pavone, an MQ-9 pilot with the 110th Wing, speaks during a training scenario through a plexiglass barrier to Staff Sgt. Justin Brandt, an MQ-9 sensor operator at the Battle Creek Air National Guard Base, Battle Creek, Michigan. The plexiglass mitigates risk of coronavirus transmission during the pandemic. (U.S. Air National Guard photo by Staff Sgt. Bethany Rizor)

Recommended Content:

Medical Surveillance Monthly Report

Surveillance of Mental and Behavioral Health Care Utilization and Use of Telehealth, Active Component, U.S. Armed Forces, 1 January 2019–30 September 2020

Article
8/1/2021
U.S. Air Force Lt. Col. Eric Oglesbee, the PACAF Pediatric Psychological Developmental Team child psychologist with the 18th Healthcare Operations Squadron, demonstrates how a telehealth appointment would operate at Kadena Air Base, Japan, April 19, 2021. Providing pediatric mental health support to five overseas Air Force bases, P3DT uses both virtual and in-person. (U.S. Air Force photo by Airman 1st Class Anna Nolte)

Recommended Content:

Medical Surveillance Monthly Report

Update: Mental Health Disorders and Mental Health Problems, Active Component, U.S. Armed Forces, 2016–2020

Article
8/1/2021
 Capt. Elrico Hernandez, battalion physician assistant for 2nd Battalion, 3rd Infantry Regiment, 3rd Stryker Brigade Combat Team, 2nd Infantry Division, discusses a training scenario that is part of the first Primary Care Behavioral Health seminar. The new program is being undertaken by medical care providers throughout United States Division-North in order to provide better mental health screening for Soldiers

Update: Mental Health Disorders and Mental Health Problems, Active Component, U.S. Armed Forces, 2016–2020

Recommended Content:

Medical Surveillance Monthly Report

Brief Report: Prevalence of Screening Positive for Post-Traumatic Stress Disorder Among Service Members Following Combat-Related Injury

Article
8/1/2021
U.S. Army Sgt. Arne F. Eastlund of the California Army National Guard’s 49th Military Police Brigade was nearly killed in 2005 in Baghdad, Iraq, during Operation Iraqi Freedom. An improvised explosive device destroyed his military vehicle and killed comrade Sgt. 1st Class Isaac S. Lawson. Eastlund survived and has continued serving Cal Guard even as a retired war veteran. (U.S. Army National Guard photo provided by Arne Eastlund)

Recommended Content:

Medical Surveillance Monthly Report

Long-Acting Reversible Contraceptive Use, Active Component Service Women, U.S. Armed Forces, 2016–2020

Article
7/1/2021
Lt. Col. Paula Neemann, 15th Healthcare Operations Squadron clinical medicine flight commander, demonstrates several birth options, such as an intrauterine device, at the 15th MDG's contraceptive clinic at Joint Base Pearl Harbor-Hickam, Hawaii, May 6, 2021. The contraceptive clinic opened June 7 to service beneficiaries and provide same-day procedures without a referral. (U.S. Air Force photo by 2nd Lt. Benjamin Aronson)

Long-Acting Reversible Contraceptive Use, Active Component Service Women, U.S. Armed Forces, 2016–2020

Recommended Content:

Medical Surveillance Monthly Report

Oral Cavity and Pharynx Cancers, Active Component, U.S. Armed Forces, 2007–2019

Article
7/1/2021
Moist snuff, chewing tobacco is placed between cheek and gum. All varieties of smokeless tobacco can cause harmful effects on the oral cavity.

Oral Cavity and Pharynx Cancers, Active Component, U.S. Armed Forces, 2007–2019

Recommended Content:

Medical Surveillance Monthly Report
<< < 1 2 3 4 5  ... > >> 
Showing results 1 - 15 Page 1 of 14

DHA Address: 7700 Arlington Boulevard | Suite 5101 | Falls Church, VA | 22042-5101

Some documents are presented in Portable Document Format (PDF). A PDF reader is required for viewing. Download a PDF Reader or learn more about PDFs.