Nasal spray for children appeared to have reduced effectiveness against the flu compared with the traditional shot, in past flu seasons, a new US study finds, CNN reports.

Results from the study were published in the journal Pediatrics.

The research involved analyzing data from several previous studies.

The flu shot  that was analyzed 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, and work by stimulating the immune system.

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.

Vaccine effectiveness against flu virus

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 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.

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.

The shot – primary choice for children

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."

Some pediatricians like Dr. Tanya Altmann, may prefer the nasal spray because that vaccine might not be as painful as a flu shot for their young patients. Dr. Altmann is founder of Calabasas Pediatrics Wellness Center in California and an American Academy of Pediatrics spokeswoman and she is  not involved in the new study.

Most important – getting vaccinated

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”q comments Dr. Altmann to CNN.

Regardless of the type of flu vaccine your family may prefer, Altmann said, what remains most important is getting vaccinated.