The 411 on Flu Vaccines

Live attenuated influenza vaccine may be less effective than inactivated vaccine among children, teens

(RxWiki News) When it comes to flu vaccines, which is better: A squirt in the nose or a shot in the arm?

A new study found that the live attenuated influenza vaccine (LAIV), more commonly known as the nasal spray flu vaccine, may be less effective at preventing the flu among children and teens than the inactivated influenza vaccine (IIV) in some cases.

The flu is a contagious disease caused by many viruses that are always changing. Each year, new flu vaccines are created to protect against three or four viruses that are likely to cause disease in the upcoming flu season.

"The effectiveness of the flu vaccine, whether given as a the live attenuated vaccine or the inactivated flu vaccine, varies each year and depends upon the 'match' between the circulating viruses and the flu vaccine’s ability to protect against these strains of influenza," said Betsy Carlisle, PharmD, CDE, a clinical pharmacy specialist for Seton Medical Center Hays, in an interview with RxWiki News. "Generally speaking, the flu vaccine works the best in healthy adults and older children."

LAIV contains a weakened form of the flu virus and is sprayed directly into the nose. IIV contains an inactive form of the virus and is given by needle.

For this study, a team of researchers led by Jessie R. Chung, MPH, used data from the US Influenza Vaccine Effectiveness Network to look at 6,819 children and teens ages 2 to 17 who were vaccinated with LAIV or IIV during four flu seasons between 2010 and 2014.

The chances of getting the flu were similar for both children and teens vaccinated with LAIV or IIV across three seasons: 2010–2011, 2011-2012 and 2012–2013. In 2013–2014, however, the chances of flu were significantly higher among young children (ages 2 to 8) vaccinated with LAIV.

Patients vaccinated with LAIV or IIV also had similar odds of illness tied to influenza A/H3N2 or influenza B. Patients vaccinated with LAIV had greater odds of illness due to influenza A/H1N1pdm09.

In other words, LAIV was less effective than IIV at protecting against influenza A/H1N1pdm09 but not influenza A/H3N2 or B among children and teens.

Researchers said that, while the reasons behind these findings are not yet understood, it will likely be important to monitor specific flu types in the future as vaccination rates increase and new vaccines are introduced.

"Influenza vaccine effectiveness can vary with changes in vaccine components or circulating influenza viruses and requires ongoing evaluation to inform vaccine recommendations," Chung and colleagues wrote.

While flu symptoms typically go away within a few days, the flu can lead to pneumonia and other life-threatening complications in some patients. Thousands of people die and many more are hospitalized each year in the US from the flu, according to the Centers for Disease Control and Prevention (CDC).

This study was published Jan. 5 in the journal Pediatrics.

The CDC, the University of Michigan, the University of Pittsburgh, Baylor Scott and White Health, and the University of Rochester funded this research.

Several study authors disclosed ties to companies that make vaccine products.

Review Date: 
January 4, 2016