Is the Flu Shot More Effective than the Nasal Spray Vaccine?

The nasal spray flu vaccine was less effective than the flu shot among patients aged 2 to 17 years old during the 2013-2014 flu season, according to 2 new studies.

The 2 studies compared the effectiveness of the live attenuated influenza vaccine (LAIV)—the nasal spray—and the inactivated influenza vaccine (IIV)—the flu shot.
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For the first study, researchers analyzed 2703 patients aged 2 to 17 years old from the U.S. Influenza Vaccine Effectiveness Network from 2010 to 2014. About 24% of patients received the LAIV and 76% received the IIV over the 4 flu seasons.

After examining electronic medical records, researchers found that results were similar across age groups and vaccines for the first 3 seasons, but results for the 2013-2014 season—which was dominated by the A(H1N1)pdm09 strain—showed that the LAIV was significantly less effective than the IIV in patients aged 2 to 8 years old.

“We observed lower effectiveness of LAIV compared with IIV against influenza A(H1N1)pdm09 but not A(H3N2) or B among children and adolescents, suggesting poor performance related to the LAIV A/H1N1pdm09 viral construct,” researchers concluded.

For the second study, researchers analyzed 5637 patients older than 6 months from the U.S. Flu Vaccine Effectiveness Network for the 2013-2014 flu season only. They tested the effectiveness of the IIV in children older than 6 months and the LAIV in children aged 2 to 17.

Researchers found that the LAIV was only 17% effective in children aged 2 to 17 years old, and the IIV was 60% effective in that age group.

“During 2013–2014, IIV was significantly effective against A(H1N1)pdm09,” researchers concluded. “Lack of LAIV4 effectiveness in children highlights the importance of continued annual monitoring of effectiveness of influenza vaccines in the United States.”

--Amanda Balbi

References:

  1. Chung JR, Flannery B, Thompson MG, et al. Seasonal effectiveness of live attenuated and inactivated influenza vaccine. Pediatrics. February 2016.
  2. Gaglani M, Pruszynski J, Murthy K, et al. Influenza vaccine effectiveness against 2009 pandemic influenza A(H1N1) virus differed by vaccine type during 2013–2014 in the United States. J Infect Dis. January 6, 2016. doi:10.1093/infdis/jiv577.