The CDC reaffirms its decision to pull the intranasal vaccine, but allow vaccination in egg-allergic individuals.
Two big changes have been made to this year’s influenza vaccination recommendations-one regarding the discontinuation of the intranasal formulation, and another that applies to individuals with egg allergies.
The Centers for Disease Control and Prevention (CDC) released updated guidelines on influenza vaccination for the 2016-2017 season, with the primary change building upon an earlier announcement to abandon the intranasal formulation of the vaccine after it was found to be substantially less effective than the injectable formulation.
CDC’s Advisory Committee on Immunization Practices (ACIP) voted against using the live attenuated influenza vaccine (LAIV)-administered intranasally-for the upcoming flu season earlier this summer due to poor performance between 2013 and 2016.
According to data from the U.S. Influenza Vaccine Effectiveness Network, the intranasal spray showed an estimated 3% effectiveness rate during the 2015-16 season compared to a 63% effectiveness rate for the injectable vaccine.
Although there is no clear reason as to why the efficacy of the intranasal vaccine decreased since it was introduced in 2003 until recent years, CDC said it may be due to a change in the formulation of the vaccine. The efficacy of the intranasal vaccine began to change 3 years ago when coverage was added against a fourth strain of the influenza virus, according to CDC. Whether there is some kind of interference among the viruses making it less effective is uncertain.
Manufacturers had projected to supply as many as 14 million doses of intranasal vaccine for the 2016-17 flu season, accounting for 8% of the more than 170 million total projected doses. Despite the loss of the intranasal vaccine supply, there are no anticipated shortages in this season’s supply of flu vaccines.
The other major change applies to individuals with egg allergies, for whom the vaccine was previously contraindicated.
Allergic reactions in individuals with egg allergies have historically been rare, according to CDC, with about 1.31 reactions per 1 million vaccine doses. Additionally, CDC cites a 2012 study that reviewed inoculation of 4,172 egg-allergic patients with the LAIV flu vaccine during which no anaphylaxis-only mild reactions-occurred. Other studies have demonstrated similar results.
For this flu season, ACIP recommends that egg-allergic individuals whose reactions have been limited to hives may receive the influenza vaccine in the same manner as the general population. Those who have had more severe reactions-including anaphylaxis requiring epinephrine or other emergency intervention-may also receive the vaccine this year, but administration should occur in an inpatient or outpatient setting where a healthcare provider can monitor and treat the individual for a reaction, if necessary. Egg-allergic individuals should be monitored for at least 30 minutes, and the CDC even recommends that individuals without egg allergies be observed for at least 15 minutes to rule out any adverse effects to the vaccine, including syncope.
Previous allergic reactions to the vaccine itself-rather than to eggs in particular-is a contraindication to the vaccine, according to the CDC.
CDC recommends that all individuals over the age of 6 months are advised to receive the flu vaccine annually, especially senior citizens and those who are immunocompromised.
The American Academy of Family Physicians (AAFP) says it supports the updated recommendations and suggests that all adults, particularly seniors, comply with the guidelines.
“The flu vaccine is one of the best ways to safeguard yourself against the flu-and getting the vaccine helps protect not only yourself but also the health of those around you,” Wanda D. Filer, MD, MBA, FAAFP, board chair of AAFP told Medical Economics.
“The AAFP is a strong proponent of vaccines as a safe and effective way to stop preventable diseases and ensure public safety. Family physicians treat patients across their lifespan, and the AAFP is dedicated to helping physicians promote the recommended schedule of vaccines for every patient.”
There have been between 3,300 and 49,000 flu deaths annually over the last 31 influenza seasons, said CDC, and the makeup of the virus changes each year, sometimes mutating throughout the season. Global experts try to predict the viruses that will be circulating most heavily in a given year, and match the vaccine to those viruses. The 2014-15 season was a particularly bad match for the vaccine with about 23% efficacy overall, compared to the 2015-16 season with 47%.
Both trivalent and quadrivalent vaccines will be available for 2016-2017 season, and CDC said either formulation is acceptable, with no preference given to one over the other. Both formulations contain an A/California/7/2009 (H1N1)pdm09–like virus, an A/HongKong/4801/2014 (H3N2)–like virus, and a B/Brisbane/60/2008-like virus (B/Victoria lineage). Quadrivalent influenza vaccines contain the B/Phuket/3073/2013-like virus (B/Yamagata lineage), according to CDC.
The flu vaccination lasts about 6 to 8 months, and individuals are encouraged to receive the vaccine by late October to ensure coverage before the onset of influenza activity, which typically peaks in January.
Last year’s flu seasons was a moderate one, peaking in March, with influenza A (H1N1)pdm09 virus, with influenza A (H3N2) dominating the season from October through December, and influenza B viruses taking over from mid-April through mid-May.