Yet among children, the nasal spray appeared to have reduced effectiveness against the flu, compared with the shot, in past flu seasons, according to a study published in the journal Pediatrics on Monday.
That finding, which involved analyzing data from several previous studies, seems to align with existing research.
"We were able to better describe vaccine effectiveness in age groups that the individual studies were not able to due to small sample sizes," said Jessie Chung, first author of the study and an epidemiologist in the US Centers for Disease Control and Prevention's Influenza Division.
The flu shot in the study is an inactivated influenza vaccine. The nasal spray, FluMist, is a live attenuated influenza vaccine. Though the viruses in FluMist are live, they have been weakened -- attenuated, in medical terms -- and work by stimulating the immune system.
MedImmune, a subsidiary of London-based AstraZeneca PLC, produces FluMist, which was approved by the US Food and Drug Administration in 2003.
Two of the new study's 10 authors are employees of AstraZeneca, but Chung said the company was not directly involved in the study's analysis.
For the 2018-19 flu season, which began in October, three types of vaccine are available in the United States: the inactivated influenza vaccine or IIV, administered as a shot; the recombinant influenza vaccine or RIV, also administered as a shot; and the live attenuated influenza vaccine or LAIV, administered as a nasal spray.
"CDC recommends annual influenza vaccination for everyone 6 months and older with any licensed, age-appropriate flu vaccine -- IIV, RIV4 or LAIV4 -- with no preference expressed for any one vaccine over another," Chung said.
For the past two flu seasons, the CDC's Advisory Committee on Immunization Practices, a panel of immunization experts, has not recommended the nasal spray. However, it was recommended again this flu season.
Dr. Pedro Piedra, a professor at Baylor College of Medicine in Houston, wrote an editorial accompanying the study in Pediatrics. He noted that the committee's latest recommendation for the use of the nasal spray was based, in part, on new manufacturer data revealing improvements to performance. That new data was not included in the new study.
Meanwhile, the American Academy of Pediatrics recommends the inactivated flu shot as the primary choice for children "because it has provided the most consistent protection against all strains of the flu virus in recent years."
The new study included data from five previously published studies on vaccine effectiveness during the 2013-14 and 2015-16 flu seasons. The data included 17,173 children, ages 2 to 17, from 42 states.
After combining data from all flu seasons, the researchers found that vaccine effectiveness against any type of flu virus was 51% for the inactivated flu shot vs. 26% for the nasal spray.
The study had some limitations, including that it relied on information provided in those previously published data.
"Despite combining data, we were still limited by sample size in some of our analyses," Chung said. Additionally, more research is needed to determine whether similar findings would emerge in data from other flu seasons.
Some pediatricians, including Dr. Tanya Altmann, may prefer the nasal spray because that vaccine might not be as painful as a flu shot for their young patients. Of her three sons, Altmann said, two were given the FluMist this year, and one was given the shot.
"I've been practicing now for almost 20 years, and I did use the FluMist a lot when it was available, and I found that patients liked it because it wasn't a shot -- and, despite the study, I always felt like in my clinical practice it worked about as well as the shot," said Altmann, founder of Calabasas Pediatrics Wellness Center in California and an American Academy of Pediatrics spokeswoman, who was not involved in the new study.
"The study did not include this current flu season, which from my understanding is a newly formulated FluMist vaccine. So the FluMist vaccine that I'm giving today in my office this season is different from the one that was studied. Only time will tell how effective the current FluMist vaccine is," said Altmann, who is also author of the book "Baby and Toddler Basics."
"I'm still hopeful," she added. "I have no connection with the company. I just feel like it's a good option, and I like the changes they made, and I want to give it another chance."
Regardless of the type of flu vaccine your family may prefer, Altmann said, what remains most important is getting vaccinated.
Nineteen states have high levels of flu activity, and 13 flu-related pediatric deaths have been reported during the current season so far, according to numbers the CDC released Friday.
While a flu vaccine is not 100% effective, it does lessen the severity of symptoms and the duration of illness in those who might get the flu.
"We know hands-down that getting any flu vaccine is better than getting no flu vaccine. So talk to your pediatrician or your doctor about what's available this season," Altmann said. "It's not too late to still get a flu vaccine if you haven't already because the flu is here. It's everywhere, and it's rapidly spreading and very contagious."
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