Story Highlights

• The CDC recommended against using the live nasal spray FluMist vaccine for the previous two “flu seasons” due to its ineffectiveness against the H1N1 strain.
• The CDC has done an about-face for the 2018-2019 “flu season” and is back to recommending FluMist again.
• The CDC’s new recommendation to use FluMist is not backed by proof that the new formulation of FluMist works as advertised.

In February 2018, the U.S. Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices (ACIP) voted to re-recommend the live virus nasal spray influenza vaccine, FluMist, for the 2018-19 “flu season” after a two-year hiatus.1 FluMist, manufactured by MedImmune/AstraZeneca, was first licensed in the U.S. in 2003 as a trivalent vaccine and was approved for use in healthy children and adults between the ages of five to 49 years old.2 The live attenuated influenza vaccine (LAIV) is popular, particularly with children, since it is sprayed up the nose and does not require a needle for administration.

The ACIP voted against recommending the quadrivalent FluMist for the 2016-17 and 2017-18 influenza seasons due to the vaccine’s ineffectiveness in protecting against the H1N1 strain (Influenza A).2 According to the CDC:

While data from 2010-2011 through 2016-2017 indicated that LAIV lacked effectiveness among 2 through 17-year-olds against H1N1pdm09 influenza viruses (2009 H1N1) in the U.S., LAIV was effective against influenza B viruses, and was similarly effective against H3N2 viruses as inactivated influenza vaccines.3

Effectiveness of influenza vaccines varies every year because the influenza virus mutates rapidly and there are many strains. Flu vaccines must be manufactured each “flu season” to match the circulating strains of influenza that health officials predict will be most prevalent. The CDC has stated:

How well the flu vaccine works (or its ability to prevent flu illness) can range widely from season to season and can be affected by a number of factors, including characteristics of the person being vaccinated, the similarity between vaccine viruses and circulating viruses, and even which vaccine is used.4

In 2017, data from a study published in The New England Journal of Medicine supported the federal recommendation that live virus FluMist should not be used on patients in the U.S.5 Brendan Flannery, PhD, author of the study and epidemiologist at the CDC’s Influenza Division discusses why the FluMist vaccine was ineffective during the 2015-16 season:

The simple explanation is that the vaccine virus in the live vaccine didn’t work the way it should have worked, whereas in the inactivated vaccine, that same virus worked well against the circulating viruses.”6

He adds that, “When the virus was killed in the inactivated vaccine, it worked. When it was a live vaccine, that live virus didn’t perform like a live virus. Something happened.”6

Live virus vaccines are known to cause vaccine strain virus infections, shedding and transmission.7 It is important to note that there are cases reported in the medical literature that FluMist has resulted in shedding and transmission of vaccine strain influenza virus.8

Why Did ACIP Reinstate FluMist for the 2018-19 “Flu Season”?

The ACIP meets three times a year to review and discuss new evidence on vaccines and make adjustments to the recommended vaccine schedule based on this evidence.2 In February 2018, the ACIP members voted 12-2 to include FluMist LAIV4 as an option for influenza vaccination for the 2018-19 influenza season for children and adults. In a 14-0 vote, the vaccine was also added back into the Vaccine For Children Program (VFC),9 which is a federally funded program that provides vaccines at no cost to children who might not be vaccinated because of inability to pay.

Studies have shown that that effectiveness of LAIV in previous years was approximately 45 percent against Influenza A and B with 25 percent protection against Influenza A (H1N1pdm09) when compared with unvaccinated children.9 Researchers also found that although the inactivated influenza vaccine was “better” in all age groups against Influenza A (H1N1pdm09) when compared with LAIV, there was no statistically significant difference in protection between the two vaccines for the Influenza A (H3N2) and Influenza B viruses.9

This year, Raburn Mallory, MD, a representative from MedImmune/AstraZeneca attended the ACIP meeting to present information and data to the CDC’s vaccine policymaking committee on a new formulation of the nasal spray vaccine and the ways in which the manufacturer has corrected errors that were encountered in the prior version.9

According to the American Academy of Pediatrics (AAP):

On Wednesday, Raburn Mallory, M.D., senior director of clinical development for FluMist manufacturer MedImmune, told the committee it had changed to a new H1N1 strain (A/Slovenia) that is producing better antibody responses than the previous strain (A/Bolivia). He also presented data on shedding of the vaccine strain and on seroconversion. However, because there has been little circulation of influenza A/H1N1 in the past two years, there are no efficacy data for the new formulation against H1N1 which was the strain for which LAIV performed poorly in the 2013-’14 and 2015-’16 seasons.10

As AstraZeneca’s Dr. Mallory has clearly pointed out, the problem is that there is no vaccine efficacy data available on the new formulation of LAIV4 and it is unknown whether FluMist will be effective this flu season. Lisa Grohskopf, MD at the CDC acknowledged this by stating that, “effectiveness is likely to remain unknown until the next H1N1-predominant season” and that decisions to recommend influenza vaccines “is not generally based upon effectiveness comparisons to other products.”10

News reports highlight that ACIP’s discussion was centered on giving FluMist another try.9 One of the “No” votes was that of Henry Bernstein, DO, at Zucker School of Medicine at Hofstra/Northwell. Berstein expressed his concerns by stating the following:

The part that really worries me the most is the fact if we reinstate LAIV4 without knowing its vaccine effectiveness during an H1N1 season and then we have an H1N1 season and it results in increased morbidity and mortality … that is likely to undermine administration of flu vaccine for the public, potentially lowering all coverage rates and negatively impacting the country’s overall flu vaccine program.10

The second “No” vote was from David Stephens, MD, at Emory University School of Medicine. Stephens stated, “I’m really concerned about what message this [approval] sends.”9

Interestingly, the AAP has expressed the strongest concerns regarding the reinstating of FluMist. According to an article published on MedPage Today:

AAP liaison member David Kimberlin, MD, of the University of Alabama Birmingham, pointed out that the CDC meta-analysis was “too blended” to pull out strong consideration that LAIV has the kind of effectiveness they are hoping for. Also, the shedding data presented by the manufacturer does not correlate with effectiveness, he said.9

Dr. Kimberlin further added, “If we have an H1N1 year, and this vaccine has been recommended for use again and it doesn’t work, that’s a sobering sentence for me.”9

In response, ACIP committee member Edward Belongia, MD, at the Center for Clinical Epidemiology and Population Health in Wisconsin pointed out that decisions to recommend influenza vaccines are generally based on immunogenicity and not effectiveness. He stated, “Given what we know, this is a reasonable approach. We always have to make the decision based on the best science available at the time, and I do think the manufacturer has made a good faith effort to understand the root causes of what was going on.”9

Despite the fact that the efficacy and effectiveness of this vaccine is unknown, another ACIP member Cynthia Pellegrini, senior vice president of public policy and government affairs for March of Dimes stated, “I think the evidence is pretty clear this vaccine is better than not being vaccinated and there are kids who will not be vaccinated without this option…”10

The ACIP also voted against giving preferential treatment to the inactivated influenza vaccine and the recombinant influenza vaccine over LAIV4.8 According to Laura Riley, MD, at Massachusetts General Hospital in Boston, the reason cited for voting against giving the other influenza vaccines preference over LAIV4 is, “We need to give people as many options to be vaccinated, because being vaccinated is better than not being vaccinated.”9

The assumption that using FluMist is better than not being vaccinated given the lack of data on the efficacy of LAIV4 is not rational because it is not based on scientific evidence.

The AAP is Encouraging Parents to Opt for Other Influenza Vaccines Instead of FluMist

Given the AAP’s objection to reinstating FluMist, the organization is recommending that children should be vaccinated with injectable influenza vaccines rather than FluMist. (It is important to note that injectable influenza vaccines also have their own set of problems that the CDC and AAP choose to ignore.) This recommendation conflicts with that of the CDC’s recommendation of FluMist. ACIP member Henry Bernstein, MD said:

The AAP feels that the flu shot should be the primary vaccine choice for all children.” He goes on to add, “There’s no question that ideally we would like for the CDC and the AAP to be completely harmonized. Both groups are harmonized in wanting as many children to receive flu vaccine as possible each and every year. When recommendations are not perfectly harmonized, it does pose the possibility for confusion.11

The fact that FluMist (LAIV4) is reinstated back into the CDC’s recommended influenza vaccine schedule for children and adults, despite lack of data that it actually works to prevent influenza, calls into question the CDC’s commitment to ensuring that all recommended vaccines are safe and effective.