Investigators have found the IIV4 vaccination to be as effective as IIV3-SD, while IIV3-HD was found to be more effective than IIV3-SD.
While quadrivalent influenza vaccines (IIV4) have been found to be as effective as the trivalent standard-dose (IIV3-SD) in a recent comparative trial of influenza vaccines, the high-dose trivalent vaccine (IIV3-HD) was also found to be more effective than IIV3-SD.
At the annual 2018 IDWeek meeting in San Francisco, CA, data regarding the clinical effectiveness of the vaccine strains among patients from the Veterans Health Administration (VHA) sought to establish the relative vaccine effectiveness (rVE) of IIV3-HD and IIV4 versus IIV3-SD. The study came in response to the US Advisory Committee on Immunization Practices' lack of recommendation of one vaccine over another, investigators noted.
The study included 782,346 veterans aged 65 years and older were administered an IIV during the 2014-2015 influenza season. To capture the study outcomes of hospitalizations and baseline characteristics, electronic medical records from the VHA were linked with Centers for Medicare and Medicate Services administrative claims.
To adjust for potential confounding due to unmeasured factors associated with IIV3-SD, IIV3-HD, or IIV4 vaccination, the inverse probability of treatment weight (IPTW) method was used. Patient socio-demographic characteristics, comorbidities, pre-influenza season hospitalizations, prior season influenza vaccination, and use of immunosuppressive medication was used to estimate the probability.
Of the 782,346 VHA patients included in the study, 10,543 (1%) were administered IIV4, 59,536 (8%) were administered IIV3-HD, and 712,267 (91%) were administered IIV3-SD.
Additionally, 588,324 (76%) of the study population were non-Hispanic white, and 11,626 (1.5%) patients were female.
In comparison to those administered IIV3-SD, the IPTW-adjusted rVE for IIV3-HD was 7% (95% CI, 9%-21%) against all-cause, 15% (95% CI: 10 - 17) against cardiorespiratory-associated, and 13% (95% CI: 8 - 17) against influenza/pneumonia-associated hospitalization. The IPTW-adjusted rVE was 4% (95% CI: 1 - 4), 1% (95% CI: -2 to -5), and 0% (95% CI: -9 to -8) for those administered the IIV4 vaccine, respectively.
Based off of the results, investigators concluded that IIV4 is as effective as IIV3-SD, and IIV3-HD is more effective than IIV3-SD.
The study’s results come on the heels of the 2018-2019 pediatric flu prevention and treatment recommendations issued by the Clinician Outreach and Communication Activity (COCA) in a recent webinar.
Recommendations included input from both the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP).
While the organizations did not recommend 1 vaccine over another, the updated recommendations do specify that nasal spray flu vaccine (LAIV4) is now considered an option for the upcoming 2018-2019 flu season for whom it is appropriate. Previously, LAIV4 had not been recommended due to recorded low effectiveness in children aged 2-17 years during 2013-14 and 2015-16 flu seasons.
Additionally, while the AAP does not prefer any 1 vaccine over another, an IIV is recommended as the primary choice for children.
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