The relative efficacy of trivalent live attenuated and inactivated influenza vaccines in children and adults

Abstract

In the United States, two types of vaccines are recommended for the prevention of influenza: an intranasal live attenuated influenza vaccine (LAIV) for eligible individuals aged 2–49 years and unadjuvanted injectable trivalent inactivated vaccines (TIV) for eligible individuals aged ≥6 months. Several recent studies have compared the efficacy of the 2 vaccines in children and adults. In children 6 months to 18 years of age, each of the four comparative studies of LAIV and TIV demonstrated that LAIV was more protective. In individuals 17–49 years of age, most comparative studies have demonstrated that LAIV and TIV were similarly efficacious or that TIV was more efficacious. However, LAIV was shown to be more protective than TIV in new military recruits of all ages, and placebo-controlled studies in adults in 1997–1998 suggested that LAIV was more protective against the mismatched A/H3N2 strain. The relative efficacy of LAIV and TIV among young adults may vary depending on the specific population and the antigenic match between the vaccines and circulating strains. In adults 60 years of age and older, limited data suggest that the two vaccines are similarly effective. In children and adults, studies also suggest that the relative efficacy of LAIV versus TIV may increase when measured against more severe illness. Additional research comparing LAIV and TIV is needed in adults and would also be valuable in older children and adolescents. Studies should examine the role of pre-existing immunity as well as vaccine impact on influenza illness of varying severity.

2012/13 influenza vaccine effectiveness against hospitalised influenza A(H1N1)pdm09, A(H3N2) and B: estimates from a European network of hospitals

“…A 2011 review of studies comparing TIV and LAIV concluded that the two vaccines have a similar relative efficacy in the elderly, based on the currently available data. [225] In South Africa, a randomized placebo-controlled trial in 2001 estimated LAIV efficacy against vaccine-matched influenza viruses to be 42.3%, with highest efficacy against influenza A(H3N2) viruses (52.5%), no efficacy against influenza B viruses, and no increase of severe adverse events for LAIV recipients compared to placebo. [226] A superiority trial in South Africa in 2002 found no significant difference in relative efficacy between LAIV and TIV, although this was due in part to the small number of laboratory-confirmed infections in the two study arms.…”

Background paper to the recommendation for the preferential use of live-attenuated influenza vaccine in children aged 2–6 years in Germany

“…Furthermore, we identified one observational study in children aged 5-18 years [8], which we excluded from further analysis because study participants in the intervention group differed substantially in baseline risk for influenza from those in the comparison group (healthy children were vaccinated with LAIV, children with increased risk of influenza due to an underlying chronic condition were vaccinated with TIV). In addition, we found five publications with meta-analyses and/or subgroup analyses of efficacy and safety data from these three studies and placebo-controlled studies of LAIV [4,9,10,11,12], which we additionally considered in the evidence appraisal process.…”

Urgent challenges in implementing live attenuated influenza vaccine

“…Absolute efficacy in 18-49 year olds was lower than in children and efficacy was not demonstrated in the over 50s, leading to preferential recommendation for LAIV in children. 6,42 The common interpretation of this finding is that adults have prior immune history of influenza infections and possess cellular immunity to conserved internal viral proteins that can supress local mucosal replication of LAIV well enough to preclude a robust immune response. This cross-reactive immunity may be what protects many adults from severe illness during a pandemic.…”

“…4,5 More recently, live attenuated influenza vaccine (LAIV) was demonstrated to have greater efficacy than IIV in children, with absolute efficacy rates of 75-80%. [6][7][8] Internal genes of LAIV viruses are derived from a cold-adapted, attenuated strain of virus, either Ann Arbor/1960 (from the US) or Leningrad/1957 (from Russia). Haemagglutinin (HA) and neuraminidase (NA) surface antigens are engineered to be representative of currently circulating strains.…”