There are 24 flu vaccines approved by the U.S. Food and Drug Administration, but sometimes more choice just leads to more confusion.
There are a lot of options when it comes to flu vaccines, and now is the time to start thinking about—and better understanding—the differences.
“A variety of influenza vaccines exist, and it can be confusing to physicians and pharmacists on which vaccine is appropriate for each patient,” said Annie L. Wirtz, PharmD, BCPPS, a pediatric infectious disease and antimicrobial stewardship clinical pharmacy specialist at Children’s Mercy Hospital. “Influenza vaccines can be divided into inactivated and live-attenuated vaccines. Each specific vaccine has certain populations it is recommended in and some have certain populations where use should be avoided.”
Here are the various options for influenza vaccination and their indications, according to Wirtz.
This is a live-attenuated influenza vaccine (LAIV4), and was recommended for the 2018-19 flu season and again for the 2019-20 season after a brief hiatus. FluMist had been pulled from the recommended vaccine list from 2016 to 2018 over evidence of decreased efficacy against the H1N1 influenza strain.
“It was reformulated and utilized within the last influenza season,” Wirtz said. “Data on the reformulated formulation supported its use.”
FluMist is not for everyone, though. The intranasal mist is licensed for individuals aged 2 to 49, but since it’s a live vaccine, there are some additional restrictions. Immunosuppressed patients, pregnant women, patients receiving influenza antiviral medications, and children with a diagnosis of asthma with a wheezing episode in the past year should not receive this vaccine formulation, Wirtz said. The preferred use is for patients without these exceptions who are afraid of needles and might not get the vaccine otherwise, she said.
Inactivated influenza vaccines
There are 22 inactivated flu vaccines on the market, including Afluria, AgriFlu, Fluad, Fluarix , Flucelvax, Flulaval, Fluvirin, Fluzone, and Flublok, plus several generic vaccines, according to the FDA.
Some are monovalent–primarily the generic vaccines—meaning that they are only used against one strain of influenza. Several are trivalent vaccines, formulated using two different influenza A strains and one influenza B strains. These can be used against both influenza A and B and includeAgriflu, Fluad, Fluarix, Flublok, Flulaval, Fluvirin,and Fluzone/FluZone High-Dose/Fluzone Intradermal.
Quadrivalent vaccines protect against four strains of the flu, and are formulated using two strains of influenza A and two trains of influenza B. These vaccines include Afluria , Fluarix Quadrivalent, Flublok Quadrivalent, Flucelvax , Flulaval Quadrivalent, and Fluzone Quadrivalent.
As far as particular indications, Wirtz said there are some unique differences between the formulas. For example, Flulaval and Fluzone are both recommended in patients older than 6 months of age, and neither is recommended over the other, but Fluzone has two specific formulations—0.25 mL and 0.5 mL for different age ranges, whereas Flulaval only has a standard 0.5 mL dose regardless of age.
“For us in a pediatric hospital, we worry about errors where the incorrect vaccine dose could be administered to the wrong age of patient,potentially underexposing them,” Wirst said. “We have used Flulaval with the single dose to prevent this from occurring.”
There are other unique indications, as well. Flublock is completely egg-free and propagated in insect cells, but Wirtz points out that any flu vaccine can be administered regardless of egg allergy. However, Wirtz said where Flublok stands out is that it may provide better protection for patients aged 50 and above.
“There is no recommendation from the ACIP for the 2018-2019 season stating Flublok is preferred in this population,” Wirtz added. “Fluzone High-Dose is the influenza vaccine formulation recommended for adults 65 years and older. It contains four times the antigen of standard dose influenza vaccine. Per ACIP recommendations, any vaccine formulation either standard or high dose is recommended in patients 65 years and older.
Fluad is also indicated for patients aged 65 and older, according to Seqirus, the vaccine’s manufacturer.
Flucelvax is another unique formula. A cell culture-based vaccine, this formula is propagated in canine renal cells rather than in eggs, Wirtz said. Seqirus officials said this vaccine is completely egg-free as of the 2019-20 season.
Primarily, clinicians should be weighing decisions on which vaccine to use based on age and health status of each patient, specifically taking into consideration conditions that may affect that patient’s own immune systems.