Which is more effective: live attenuated influenza vaccine or inactivated influenza vaccine?

The live attenuated influenza vaccine was not effective against influenza A or B in the 2015–2016 flu season. The Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices recently recommended against the use of live attenuated influenza vaccine (LAIV) for the 2017–2018 flu season. (LOE = 3b)

Jackson ML, Chung JR, Jackson LA, et al. Influenza vaccine effectiveness in the United States during the 2015–2016 season. N Engl J Med 2017;377(6):534-543.  [PMID:28792867]

Case-control

Government

Outpatient (any)

Both LAIV and the inactivated influenza vaccine (IIV) have been approved for use in children and adults aged 2 to 49 years. However, in the 2013–2014 flu season, the LAIV had poor activity against certain strains of influenza A (H1N1). This was thought to be due to poor heat stability of that strain, and it was changed to a new strain for the 2015–2016 season. This sentinel surveillance study assessed the effectiveness of quadrivalent LAIV in comparison with trivalent and quadrivalent IIV. The investigators from the CDC recruited persons 6 months and older with an acute respiratory illness at sentinel practices in 5 states across the country. Immunization status was determined by careful review of medical records and patient report, and a nasal and/or oropharyngeal swab was tested for influenza A or B using reverse transcriptase polymerase chain reaction. The odds ratio (OR) for infection among vaccinated versus unvaccinated children was determined, and then used to determine vaccine effectiveness. Effectiveness was determined using a "test-negative design," in which effectiveness = (1 - OR) × 100. For example, if the odds ratio was 0.30 for infection with vaccination, effectiveness was 70%, and if it was 0.60, effectivness was 40%. A total of 6879 patients were recruited, of whom 1309 (19%) tested positive for influenza. The effectiveness of trivalent IIV was 41%, that of quadrivalent IIV was 54%, and that of LAIV was only 4% (nonsignificant). The difference between quadrivalent and trivalent IIV was not statistically signficant (OR for infection for trivalent IIV compared with quadrivalent = 1.2; 95% CI 0.8 - 1.7). LAIV was not effective for any subgroup, including children aged 6 months to 17 years.