The 2018-2019 flu season has been off to a slow start, but that doesn’t mean patients should skip getting a flu shot or that pharmacists can skimp on recommending them. “Flu activity has been low so far this year, but we expect activity will pick up soon and peak between December and February,” said Alicia Budd, MPH, an epidemiologist in the Influenza Division of the CDC’s National Center for Immunization and Respiratory Diseases.
According to Budd, Influenza A (H1N1) is the predominant flu virus circulating so far this season. “Last season the flu vaccine reduced H1N1 risk by 65%.”
The success of any season’s flu vaccine depends on how well it matches the three or four viruses most likely to strike. As viruses evolve, vaccines are updated to counter new strains.
The roster of approved vaccines for the 2018-2019 season includes inactivated injectable vaccines (IIV), recombinant flu vaccines (RIV), and live attenuated vaccine (LAIV), which was omitted last year. The CDC expresses no preference, as long as vaccines are licensed and age-appropriate.
Trivalent or Quadrivalent?
Although trivalent and quadrivalent vaccines are both available this season, manufacturers estimate that up to three-quarters of the flu vaccines administered this seasons will be quadrivalent because the vaccine’s extra component protects patients from another strain of influenza.
Trivalent flu vaccines are designed to protect against three virus strains, two A viruses (H1N1 and H3N2) and one B virus, but there’s often more than one B virus circulating during any flu season. Quadrivalent vaccines offer more protection by adding a second strain of B virus.
Although quadrivalent flu vaccines offer broader protection, the CDC does not recommend waiting in the event there’s a shortage. Getting a trivalent flu shot when you can is considered more effective than waiting for a quadrivalent vaccine.
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What’s Changed This Season?
Both trivalent and quadrivalent vaccines contain the same H1N1 virus as last season. Updates were made to the H3N2 virus, and the B virus is a different strain from last year.
Components in this year’s trivalent vaccine are:
Quadrivalent vaccines feature an additional B virus:
This year’s trivalent vaccines come in a standard dose for ages 18 through 64 and a stronger dose for people over 65 because a higher dose of flu vaccine is more effective in older adults.
A cell-based flu vaccine offers options for patients with egg allergies since this type is grown in mammalian cells rather than in chicken eggs. The virus may contain traces of albumin, so people with history of severe egg allergy should be vaccinated in a doctor’s office, where any allergic reaction can be monitored and treated.
Patients who don’t like needles can get the trivalent flu vaccine via an intradermal shot, which inserts medicine under the skin, or a jet injector, which uses a high-pressure stream of fluid.
Nasal sprays are also back on the approved vaccine list due to an improvement in formula. A quadrivalent nasal-spray vaccine is now recommended for non-pregnant individuals who are two years through 49 years of age.
There are some important exclusions with the nasal-spray vaccine. Children age two through 17 who take aspirin- or salicylate-containing medications; as well as children age 2 to 4 who have asthma; and anyone with a weakened immune system, should not be administered the nasal vaccine.
Even though flu season is already underway, immunization is still recommended for everyone over six months of age. Flu shots are especially important for young children, adults 65 years of age and older, pregnant women, and people with asthma, diabetes and heart disease.
“So far six flu-related pediatric deaths have been reported this flu season,” Budd said. “Each season most pediatric deaths are in children who aren’t vaccinated.
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Flu Vaccination Can Reduce the Risk of Flu-Associated Hospitalization.
Here are the results of some recent studies: