Live Attenuated or Inactivated Influenza Vaccines and Medical Encounters for Respiratory Illnesses Among US Military Personnel

Abstract

ILITARY PERSONNEL ARE prone to outbreaks of respiratory illness such as influenza for a variety of reasons, including crowding and stressful conditions. 1-3 Before the availability of an influenza vaccine, the military population experienced high mortality and morbidity during such outbreaks. Trivalent inactivated vaccine (TIV), administered intramuscularly, was first developed and tested in the military in the 1940s and has been used annually since the 1950s to prevent influenza and its complications. 4 In 2003, a live attenuated influenza vaccine (LAIV) with the same antigenic characteristics as TIV was formulated for intranasal application and approved for use among healthy adults. Service members were immediately targeted for LAIV use by the US Department of Defense (DOD) because of the ease of vaccine administration and availability early in the season. During the TIV vaccine shortage in 2004, the DOD agreed to preferentially use LAIV to increase the availability of TIV. 5 Although TIV remained the predominant vaccine until the 2006-2007 season, LAIV has increasingly become the preferred vaccine for service members while TIV is reserved for those with higher risk for respiratory diseases or contraindications to LAIV. 6,7 Recent clinical trials comparing LAIV with TIV suggest that LAIV has superior efficacy over TIV among young

Prevention and Control of Seasonal Influenza with Vaccines

“…In a randomized, double-blind, placebocontrolled trial conducted among young adults during the 2004-05 influenza season, when the majority of circulating A(H3N2) viruses were antigenically drifted from that season's vaccine viruses, the efficacy of LAIV3 and IIV3 against cultureconfirmed influenza was 57% (95% CI = -3-82) and 77% (95% CI = 37-92), respectively. The difference in efficacy was not statistically significant and was attributable primarily to a difference in efficacy against influenza B (256) (260). However, in a retrospective cohort study comparing LAIV3 and IIV3 among 701,753 nonrecruit military personnel and 70,325 new recruits, among new recruits, incidence of ILI was lower among those who received LAIV3 than IIV3.…”

Comparisons of the Humoral and Cellular Immune Responses Induced by Live Attenuated Influenza Vaccine and Inactivated Influenza Vaccine in Adults

“…Three randomized, controlled efficacy trials in children of Ͼ6 months and Յ18 years of age consistently demonstrated that LAIV was significantly more protective than IIV (4)(5)(6)(7). Similarly, for adults older than 16 years, some comparative trials showed that LAIV was at least as effective as IIV (8)(9)(10). However, 2 adult trials showed that IIV was more protective than LAIV (11)(12)(13), and thus there is some controversy over whether LAIV can be as effective as a well-matched IIV seasonal vaccine for adults with previously extensive influenza virus exposure (2,14).…”

Deliberate reduction of hemagglutinin and neuraminidase expression of influenza virus leads to an ultraprotective live vaccine in mice

“…In contrast, LAIVs induce both humoral and cellular immunity, but are restricted for use in persons aged 2-49 y (6,7). Moreover, recurrent administration of LAIVs, which use the same attenuating viral backbone, could result in tolerance in repeat recipients (8).…”