CDC: Nasal Spray Flu Vaccine Not Very Effective

Experts from the Advisory Committee on Immunization Practices (ACIP) have advised against the use of nasal spray influenza vaccine after being proven to be not very effective in the past three flu season.

"In the absence of data demonstrating consistent greater relative effectiveness of the current quadrivalent formulation of LAIV, preference for LAIV over IIV is no longer recommended. ACIP will continue to review the effectiveness of influenza vaccines in future seasons and update these recommendations if warranted," CDC explained on Morbidity and Mortality Weekly Report.

The retraction of endorsement was made after a study from the Centers for Disease Control and Prevention revealed that the nasal spray version of influenza vaccine, also known as live attenuated influenza vaccine (LAIV), has not performed as well as expected against the H1N1 virus in 2009 flu season. Another large study showed that LAIV was also unable to work well against the drifted H3N2 virus during the 2014 to 2015 flu season.

According to the report from Center for Infectious Disease Research Policy of the University of Minnesota, ACIP recommended the use of LAIV, which is developed by AstraZeneca's MedImmune and sold under the name FluMist in June 2014 due to its relative efficacy compared to Inactive Influenza Vaccine (IIV) or commonly known as the flu shots.

However, FluMist only recorded to be three percent effective last flu season, which mean no protective benefit could be measdure at all. On the other hand, IIV had a protective effectiveness estimate of 63 percent against any flu virus among children 2 years through 17 years.

CDC now recommends that LAIV should not be used for children less than two years of age and older adults over 49 years old. People that are immunocompromised, pregnant women and persons with history of egg allergy were also advised not to take the LAIV. Also, if a person has taken influenza antiviral medications within the previous 48 hours, it is recommended that he will not take LAIV.

Still, CDC advise consumers to be vaccinated against influenza every year, despite the low effectiveness of vaccines in the market.

"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," CDC explained in NBC News.