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FluMist Trivalent Influenza Intranasal Vaccine is a nasal spray. FluMist Trivalent contains three vaccine virus strains: an A/H1N1 strain, an A/H3N2 strain and a B strain from the B/Victoria lineage.
FluMist Trivalent is a colorless to pale yellow suspension and is clear to slightly cloudy.
Each pre-filled refrigerated FluMist Trivalent sprayer contains a single 0.2 mL dose. The tip attached to the sprayer is equipped with a nozzle that produces a fine mist that is primarily deposited in the nose and nasopharynx.
Each 0.2 mL dose contains 106.5-7.5 FFU (fluorescent focus units) of live attenuated influenza virus reassortants of each of the three strains: A/Norway/31694/2022 (H1N1) (an A/Victoria/4897/2022 (H1N1)pdm09 - like virus), A/Norway/16606/2021 (H3N2) (an A/Darwin/9/2021 (H3N2) - like virus), and B/Austria/1359417/2021 (B/Victoria lineage) (a B/Austria/1359417/2021 (B/Victoria lineage) - like virus).
The influenza virus strains in FluMist Trivalent are (a) cold-adapted (ca) (i.e., they replicate efficiently at 25°C, a temperature that is restrictive for replication of many wild-type influenza viruses); (b) temperature-sensitive (ts) (i.e., they are restricted in replication at 37°C (Type B strain) or 39°C (Type A strains), temperatures at which many wild-type influenza viruses grow efficiently); and (c) attenuated (att) (i.e., they do not produce classic influenza-like illness in the ferret model of human influenza infection).
No evidence of reversion has been observed in the recovered vaccine strains that have been tested (135 of possible 250 recovered isolates) using FluMist Trivalent [see Pharmacology: Pharmacodynamics under Actions]. For each of the three reassortant strains in FluMist Trivalent, the six internal gene segments responsible for ca, ts, and att phenotypes are derived from a master donor virus (MDV), and the two segments that encode the two surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA), are derived from the corresponding antigenically relevant wild-type influenza viruses. Thus, the three viruses contained in FluMist Trivalent maintain the replication characteristics and phenotypic properties of the MDV and express the HA and NA of wild-type viruses. For the Type A MDV, at least five genetic loci in three different internal gene segments contribute to the ts and att phenotypes. For the Type B MDV, at least three genetic loci in two different internal gene segments contribute to both the ts and att properties; five genetic loci in three gene segments control the ca property.
Each of the reassortant strains in FluMist Trivalent express the HA and NA of wild-type viruses that are related to strains expected to circulate during the 2023-2024 influenza season. The viruses (A/H1N1, A/H3N2 and the B strain) have been recommended by the United States Public Health Service (USPHS) for inclusion in the annual trivalent influenza vaccine formulation.
Specific pathogen-free (SPF) eggs are inoculated with each of the reassortant strains and incubated to allow vaccine virus replication. The allantoic fluid of these eggs is harvested, pooled, and then clarified by filtration. The virus is concentrated by ultracentrifugation and diluted with stabilizing buffer to obtain the final sucrose and potassium phosphate concentrations. The viral harvests are then sterile filtered to produce the monovalent bulks. Each lot is tested for ca, ts, and att phenotypes and is also tested extensively by in vitro and in vivo methods to detect adventitious agents. Monovalent bulks from the three strains are subsequently blended and diluted as required to attain the desired potency with stabilizing buffers to produce the trivalent bulk vaccine. The bulk vaccine is then filled directly into individual sprayers for nasal administration.
Excipients/Inactive Ingredients: Each 0.2 mL dose also contains 0.188 mg/dose monosodium glutamate, 2.00 mg/dose hydrolyzed porcine gelatin, 2.42 mg/dose arginine hydrochloride, 13.68 mg/dose sucrose, 2.26 mg/dose dibasic potassium phosphate, and 0.96 mg/dose monobasic potassium phosphate.
Each dose contains residual amounts of ovalbumin (<0.024 mcg/dose), and may also contain residual amounts of gentamicin sulfate (<0.015 mcg/mL), and ethylenediaminetetraacetic acid (EDTA) (<2.3 mcg/dose).
FluMist Trivalent contains no preservatives.
