Browse the corpus

Public health concerns over the potential for a devastating influenza pandemic in the near future are well known. Surveillance efforts have increased throughout the world, and much time and money have been directed toward preparedness for such a pandemic. Given that vaccination rates vary greatly among the nonmilitary population and that influenza diagnostics are sporadically available, annual influenza vaccine effectiveness studies based on laboratory-confirmed diagnoses are rare. However, evidence of locally circulating strains evading the vaccine-induced protection could be critical for early recognition and intervention. In addition, the emergence of pandemic strains within military populations has been noted. The first documented influenza outbreak in the spring of 1918, before the great influenza pandemic of 1918–19, was among recruits at Fort Riley, Kansas (1). In 1976, a unique strain of influenza (H1N1) caused an outbreak at Fort Dix, New Jersey, causing 1 death, and creating concern over spread of this nonvaccine strain (2). Highly vaccinated military populations, under close surveillance, provide the opportunity for annual calculation of influenza vaccine effectiveness, thereby benefiting global pandemic preparedness.

used an outbreak at Fort Dix, New Jersey, causing 1 death, and creating concern over spread of this nonvaccine strain (2). Highly vaccinated military populations, under close surveillance, provide the opportunity for annual calculation of influenza vaccine effectiveness, thereby benefiting global pandemic preparedness. The Study The Naval Health Research Center (NHRC) began conducting tri-service surveillance for febrile respiratory illness at military training centers in 1996; by 1999, this surveillance network had expanded to include 8 of the largest military basic training centers in the United States (3). This surveillance includes the systematic collection of throat swab specimens and clinical data (including but not limited to gender, date of birth, symptoms, influenza vaccination status, type of vaccine received, and date of vaccination) from consenting US military trainees meeting the case definition for febrile respiratory illness (oral temperature ≥100.5°F [38.0°C] and a cough or sore throat). Samples are stored locally at each site at −70°C until they are forwarded to the Naval Respiratory Disease Laboratory at NHRC for viral culture and molecular diagnostic processing. Research personnel at participating surveillance sites report the weekly number of trainees who sought care for febrile respiratory illness and total trainee populations for their respective sites, and rates for such illnesses are calculated.

ase Laboratory at NHRC for viral culture and molecular diagnostic processing. Research personnel at participating surveillance sites report the weekly number of trainees who sought care for febrile respiratory illness and total trainee populations for their respective sites, and rates for such illnesses are calculated. During the 2003–04 influenza season, we recognized the opportunity of using data from this ongoing active surveillance to estimate influenza vaccine effectiveness in protecting against both laboratory-confirmed influenza and febrile respiratory illness of any cause among US military basic trainees. Despite concerns that vaccine effectiveness during the 2003–04 season would be low because of the poor match between the components of the vaccine and the circulating strain (4), the vaccine provided good protection (94.4%) against laboratory-confirmed influenza that season (5). Annual vaccine effectiveness calculations are important as we heighten our preparedness for pandemic influenza strains; therefore, we performed similar calculations for the 2004–05 and 2005–06 seasons. During the late fall and winter seasons, all active-duty military forces are required to receive the influenza vaccine, and this policy is strictly enforced in training camps. Upon arrival, all incoming trainees receive mandatory influenza vaccination, either the trivalent inactivated influenza vaccine by injection (FluZone, Sanofi Pasteur, Lyon, France) or intranasal cold-adapted, live, attenuated influenza vaccine (CA-LAIV) spray (FluMist, MedImmune, Gaithersburg, MD, USA).

training camps. Upon arrival, all incoming trainees receive mandatory influenza vaccination, either the trivalent inactivated influenza vaccine by injection (FluZone, Sanofi Pasteur, Lyon, France) or intranasal cold-adapted, live, attenuated influenza vaccine (CA-LAIV) spray (FluMist, MedImmune, Gaithersburg, MD, USA). For this analysis, vaccine protection was assumed to begin 14 days postvaccination. Therefore, in an 8-week training program, 25% of trainees were considered “unvaccinated” at any given time, assuming immunity takes 14 days to develop. Likewise, 33% of trainees in a 6-week training program were considered unprotected by the vaccine at any time. These assumptions allow estimates of denominator data for “vaccinated” and “unvaccinated” person-weeks in calculations of vaccine effectiveness..

at any given time, assuming immunity takes 14 days to develop. Likewise, 33% of trainees in a 6-week training program were considered unprotected by the vaccine at any time. These assumptions allow estimates of denominator data for “vaccinated” and “unvaccinated” person-weeks in calculations of vaccine effectiveness.. From January through March 2006 all new trainees arriving for basic training received the influenza vaccine; all recruits already present had been vaccinated. The observation period for this analysis included January 1—March 31, 2006. However, 2 sites, Naval Service Training Command, Great Lakes, and Marine Corps Recruit Depot, San Diego, had completed vaccination by December 2005. Therefore, December was included in the observation period for those sites as well. Total person-weeks in recruit training during the observation period were obtained directly from the participating training centers. Vaccine effectiveness was calculated for both laboratory-confirmed influenza and any cause of febrile respiratory illness as follows: 100 × (1 – relative risk = 1 – [rate in vaccinated group]/[rate in unvaccinated group]). During the observation period, 6 of 8 surveillance sites had influenza activity and were included in this analysis. In 479,181 person-weeks of observation, 4,052 cases of febrile respiratory illness were reported from these 6 sites, and 722 patients were enrolled into the surveillance study (includes throat swab specimen, case data, and consent). Seventy (9.7%) specimens tested positive for influenza, by either culture or molecular techniques.

person-weeks of observation, 4,052 cases of febrile respiratory illness were reported from these 6 sites, and 722 patients were enrolled into the surveillance study (includes throat swab specimen, case data, and consent). Seventy (9.7%) specimens tested positive for influenza, by either culture or molecular techniques. Rates of laboratory-confirmed influenza were higher among unvaccinated trainees at all sites except Fort Benning, Georgia, which had only 3 cases (Figure). Overall, influenza vaccine effectiveness among US military trainees was 92% (confidence interval [CI] 85.4–95.6%) during the 2005–06 season (Table). Vaccine effectiveness against laboratory-confirmed influenza was high (range 86%–94%) in each of the past 3 seasons. Vaccine effectiveness against non–laboratory-confirmed febrile respiratory illness was lower, ranging from −10% in 2005–06 to 52% in 2004–05. Figure Incidence of laboratory-confirmed influenza by vaccination status. AFB, Air Force base; NSTC, Naval Service Training Command; MCRD, Marine Corps Recruit Depot.

Rates of laboratory-confirmed influenza were higher among unvaccinated trainees at all sites except Fort Benning, Georgia, which had only 3 cases (Figure). Overall, influenza vaccine effectiveness among US military trainees was 92% (confidence interval [CI] 85.4–95.6%) during the 2005–06 season (Table). Vaccine effectiveness against laboratory-confirmed influenza was high (range 86%–94%) in each of the past 3 seasons. Vaccine effectiveness against non–laboratory-confirmed febrile respiratory illness was lower, ranging from −10% in 2005–06 to 52% in 2004–05. Figure Incidence of laboratory-confirmed influenza by vaccination status. AFB, Air Force base; NSTC, Naval Service Training Command; MCRD, Marine Corps Recruit Depot. Table Vaccine effectiveness against laboratory-confirmed influenza among US military basic trainees, 2005–06*† Site Vaccinated person-weeks Unvaccinated person-weeks Cases in vaccinated trainees Cases in unvaccinated trainees Vaccine effectiveness (%) 95% CI Fort Jackson, SC 77,874 25,958 7 13 82.1 Fort Wood, MO 67,513 22,504 2 11 93.9 Fort Benning, GA 68,652 22,884 3 0 – Lackland AFB, TX 37,435 18,690 1 10 95.0 NSTC Great Lakes, IL 67,763 22,588 0 13 100.0 MCRD San Diego, CA 35,490 11,830 0 10 100.0 Total 354,727 124,454 13 57 92.0 (85.4%, 95.6%) *CI, confidence interval; SC, South Carolina; MO, Missouri; GA, Georgia; AFB, Air Force base; TX, Texas; NSTC, Naval Service Training Command; IL, Illinois; MCRD, Marine Corps Recruit Depot; CA, California. †Assuming 14 d before vaccine is protective.

90 11,830 0 10 100.0 Total 354,727 124,454 13 57 92.0 (85.4%, 95.6%) *CI, confidence interval; SC, South Carolina; MO, Missouri; GA, Georgia; AFB, Air Force base; TX, Texas; NSTC, Naval Service Training Command; IL, Illinois; MCRD, Marine Corps Recruit Depot; CA, California. †Assuming 14 d before vaccine is protective. Conclusions This analysis suggests that the 2005–06 influenza vaccine was highly effective in protecting US military basic trainees against laboratory-confirmed influenza. Furthermore, these data suggest that both the trivalent inactivated vaccine injection and the CA-LAIV intranasal spray were equally effective, because the Marine Corps Recruit Depot in San Diego vaccinated its trainees with CA-LAIV almost exclusively, and vaccine effectiveness at that site was 95% (vaccine effectiveness at all other sites combined = 90%). These estimates of effectiveness were supported by results of additional analyses that would be expected to bias the outcome toward the null hypothesis. For example, a 7-day lag period before immune response was considered in an alternative analysis, and it yielded similar results: the calculated vaccine effectiveness changed only slightly, from 92% to 90%. We also analyzed vaccine effectiveness, assuming that 10% fewer trainees were vaccinated at any given point, yet the calculated vaccine effectiveness was only reduced to 87%.

nsidered in an alternative analysis, and it yielded similar results: the calculated vaccine effectiveness changed only slightly, from 92% to 90%. We also analyzed vaccine effectiveness, assuming that 10% fewer trainees were vaccinated at any given point, yet the calculated vaccine effectiveness was only reduced to 87%. In contrast to the consistently high effectiveness of the vaccines against laboratory-confirmed influenza, the effectiveness against febrile respiratory illness of any cause was much lower and varied with each season (13.9% in 2003–04, 52.1% in 2004–05, and −10% in 2005–06). This lower effectiveness in 2005–06 is most likely due to the generally high proportion of adenovirus infection seen in this population (6), and the lesser effectiveness is further exacerbated by the tendency for adenoviral infections to occur beyond the second week of training. The lower vaccine effectiveness seen against febrile respiratory illness of any cause gives credence to the estimates of high vaccine effectiveness against laboratory-confirmed influenza. If a measurement bias existed, both estimates would be affected.

adenoviral infections to occur beyond the second week of training. The lower vaccine effectiveness seen against febrile respiratory illness of any cause gives credence to the estimates of high vaccine effectiveness against laboratory-confirmed influenza. If a measurement bias existed, both estimates would be affected. As a highly vaccinated population, military personnel, and basic trainees in particular, can provide critical information regarding the effectiveness of each year’s influenza vaccine formulations. Because of the annual variations of both the vaccine formulations and the circulating strains, influenza vaccine effectiveness should be evaluated annually. With the ever-rising concerns of an imminent influenza pandemic, reliable and rigorous influenza surveillance is paramount. Our existing surveillance network will allow us to repeat the methods used in this analysis each year, thus providing valuable estimates of influenza vaccine effectiveness to the public health community. Suggested citation for this article: Strickler JK, Hawksworth AW, Myers C, Irvine M, Ryan MAK, Russell KL. Influenza vaccine effectiveness among US military basic trainees, 2005–06. Emerg Infect Dis [serial on the Internet]. 2007 Apr [date cited]. Available from http://www.cdc.gov/eid/content/13/4/617.htm

As a highly vaccinated population, military personnel, and basic trainees in particular, can provide critical information regarding the effectiveness of each year’s influenza vaccine formulations. Because of the annual variations of both the vaccine formulations and the circulating strains, influenza vaccine effectiveness should be evaluated annually. With the ever-rising concerns of an imminent influenza pandemic, reliable and rigorous influenza surveillance is paramount. Our existing surveillance network will allow us to repeat the methods used in this analysis each year, thus providing valuable estimates of influenza vaccine effectiveness to the public health community. Suggested citation for this article: Strickler JK, Hawksworth AW, Myers C, Irvine M, Ryan MAK, Russell KL. Influenza vaccine effectiveness among US military basic trainees, 2005–06. Emerg Infect Dis [serial on the Internet]. 2007 Apr [date cited]. Available from http://www.cdc.gov/eid/content/13/4/617.htm Acknowledgments Contributions from the following persons are gratefully acknowledged: Viola Paulk, Laura Pacha, Sharon Cole-Wainwright, Johnnie Conolly, R.J. Newsom, Robert Greenup, Susan Wolf, Shelly Oates, Mimms Mabee, John Gomez, Patricia Rohrbeck, Lorie Brosch, Edgar Tuliao, Josephine Genese, Annie Wang, Richard Skinner, staff from the Naval Respiratory Disease Laboratory, Naval Health Research Center; the Department of Defense Global Emerging Infection Surveillance and Response System; and the Henry M. Jackson Foundation for the Advancement of Military Medicine. Finally, we thank Gregory Gray for his original leadership of recruit respiratory infection surveillance.

Disease Laboratory, Naval Health Research Center; the Department of Defense Global Emerging Infection Surveillance and Response System; and the Henry M. Jackson Foundation for the Advancement of Military Medicine. Finally, we thank Gregory Gray for his original leadership of recruit respiratory infection surveillance. Ms Strickler has coordinated epidemiologic studies for the Department of Defense Center for Deployment Health Research at Naval Health Research Center since 2000. Her research interests focus on respiratory illness among military populations.

To the Editor: Meningococcal disease in US military personnel is controlled by vaccines, the first of which was developed by the US Army (1–5). In 1985, the quadrivalent polysaccharide vaccine (MPSV-4) was implemented as the military standard. It was replaced during 2006–2008 by the quadrivalent conjugate vaccine (MCV-4). Every person entering US military service is required to receive this vaccine. Meningococcal disease incidence in active-duty US military personnel, historically far above that in the general population (6), has decreased >90% since the early 1970s, when the first vaccine was introduced (7). Over the last 5 years, incidences in the military and US general populations have become equivalent (8). Here we update previously published data (8) from the Naval Health Research Center’s Laboratory-based Meningococcal Disease Surveillance Program of US military personnel. Data-gathering methods and laboratory analyses of samples from personnel suspected of having meningococcal disease have been previously described (8). Incidences were compared by using the New York State Department of Public Health Assessment Indicator based on the methods of Breslow and Day (9).

US military personnel. Data-gathering methods and laboratory analyses of samples from personnel suspected of having meningococcal disease have been previously described (8). Incidences were compared by using the New York State Department of Public Health Assessment Indicator based on the methods of Breslow and Day (9). During 2006–2013 in US military personnel, only 1 of the 28 meningococcal disease cases for which serogroup data are available was not serogroups C or B (8 cases each) or Y (11 cases). During that period, incidence in US military personnel of 0.271 cases per 100,000 person-years did not differ significantly (p>0.05) from that of 0.238 in the 2006–2012 age-matched US general population (persons 17–64 years of age) (Centers for Disease Control and Prevention [CDC], unpub. data). During 2010–2013, meningococcal disease incidence in military personnel was 0.174 cases per 100,000 person-years, compared with 0.194 in the age-matched 2010–2012 US population. Among military personnel, only 1 case each occurred in 2011 (serogroup Y) and 2012 (serogroup B), and 3 occurred in 2013 (1 each of serogroups B, C, and Y).

13, meningococcal disease incidence in military personnel was 0.174 cases per 100,000 person-years, compared with 0.194 in the age-matched 2010–2012 US population. Among military personnel, only 1 case each occurred in 2011 (serogroup Y) and 2012 (serogroup B), and 3 occurred in 2013 (1 each of serogroups B, C, and Y). To measure the relative success of the 2 vaccines, we compared incidence among military personnel who had received MPSV-4 with that of personnel who had received MCV-4. In 2006, MCV-4 was introduced to new recruits. The proportion of military personnel who had received MCV-4, rather than MPSV-4, increased from 6% of the military population (63,000 persons) in 2006 to 64% (930,000) in 2013. By 2013, a total of 99% of new vaccinations were of MCV-4. Overall incidence in personnel receiving MCV-4 was 0.298 cases per 100,000 person-years during 2006–2013, which was lower, although not significantly lower (p>0.05), than 0.410 cases per 100,000 person-years in MPSV-4 recipients during 2000–2013.

,000) in 2013. By 2013, a total of 99% of new vaccinations were of MCV-4. Overall incidence in personnel receiving MCV-4 was 0.298 cases per 100,000 person-years during 2006–2013, which was lower, although not significantly lower (p>0.05), than 0.410 cases per 100,000 person-years in MPSV-4 recipients during 2000–2013. However, because neither vaccine covers serogroup B, excluding serogroup B cases in the vaccine-related incidence calculations might be more appropriate. Incidence in MCV-4–vaccinated personnel during 2006–2013, excluding serogroup B cases, was 0.183. Specific serogroup data are not available for 2000–2005, so to calculate non–serogroup B incidence during this period, we estimated the proportion of serogroup B cases by examining a range of estimates of serogroup B proportions derived from the true proportions in all 6-year periods during 1995–2012 in the US general population (range 21%–35%; 35% during 2000–2005) (CDC, unpub. data) and during 2006–2013 in US military personnel (range 22%–28%). Adopting (from our estimated range of serogroup B proportions) 21% as the percentage that would have made the MPSV-4–related incidence the highest, MPSV-4–related incidence (i.e., excluding serogroup B cases) during 2000–2013 would have been 0.307, which did not differ significantly from incidence of MCV-4 non-serogroup B cases (p>0.05). (Using higher percentages would have pushed the MPSV-4 estimate even closer to the MCV-4 incidence.) The Figure shows pooled incidence for 2000–2013.

nce (i.e., excluding serogroup B cases) during 2000–2013 would have been 0.307, which did not differ significantly from incidence of MCV-4 non-serogroup B cases (p>0.05). (Using higher percentages would have pushed the MPSV-4 estimate even closer to the MCV-4 incidence.) The Figure shows pooled incidence for 2000–2013. Figure Meningococcal disease incidence per 100,000 person-years in US military personnel, 2000–2013. Incidence in vaccinated personnel shown assumes that 21% of cases during 2000–2005 were caused by Neisseria meningitis sergroup B. Results of these comparisons are subject to several limitations. First, because the relative proportions of the 2 vaccines changed, a differential effect of herd immunity caused by one or the other could have differentially suppressed rates. Second, along with the decrease in the MPSV-4 population, the average time from vaccination increased relative to the period in which MPSV-4 was given, concomitant with decreasing immunogenicity. Any elevated incidence in the MPSV-4–vaccinated population since 2006 could be associated with time since vaccination. Third, the same factors involved in the decline in incidence in the US general population that began in ≈2001 might be at play in the military, confounding the vaccine effects. Fourth, as the rate of vaccine coverage in the US population increased, a higher proportion of recruits might have entered the military already vaccinated; thus, their military vaccination was essentially a booster.

eneral population that began in ≈2001 might be at play in the military, confounding the vaccine effects. Fourth, as the rate of vaccine coverage in the US population increased, a higher proportion of recruits might have entered the military already vaccinated; thus, their military vaccination was essentially a booster. Meningococcal disease incidence decreased during 2000–2013. Our data suggest that cases in MCV-4–vaccinated personnel are similar to those in MPSV-4–vaccinated personnel, regardless of whether the incidence calculation includes cases caused by serogroup B (non–vaccine covered). More extensive study is needed to confirm the relative effects of the vaccines (10). Serogroup B accounted for 5 of the 8 cases during 2012–September 2014), and prevention of disease caused by this serotype remains a challenge. Suggested citation for this article: Broderick MP, Phillips C, Faix D. Meningococcal disease in US military before and after adoption of conjugate vaccine [letter]. Emerg Infect Dis [Internet]. 2015 Feb [date cited]. http://dx.doi.org/10.3201/eid2102.141037 Acknowledgment We thank CDC’s Meningitis and Vaccine Preventable Diseases Branch for providing the US disease data. The Naval Health Research Center Meningococcal Disease Surveillance is supported by the Global Emerging Infections System division of the Armed Forces Health Surveillance Center. The meningococcal disease surveillance in the US military produces a quarterly report, which is available online: http://www.med.navy.mil/sites/nhrc/geis/Documents/MGCreport.pdf