Flu Shot Beats Flu Spray for Young Adults
Study: Adults 18-49 Who Got the Shot Half as Likely to Get Flu
WebMD News Archive
Sept. 23, 2009 -- The traditional flu shot beats out the newer flu nasal
spray in young adults aged 18 to 49, according to a new study.
''Those who got the inactivated vaccine [the traditional flu shot] were half
as likely to get the flu as those who got the live attenuated vaccine [the flu
nasal spray]," says the study's lead author Arnold Monto, MD, a professor of
epidemiology at the University of Michigan School of Public Health in Ann
Arbor. The study is published in the New EnglandJournal of
Despite those results, Monto and other experts say that getting vaccinated
against seasonal flu -- whether by the traditional injection or the newer nasal
spray -- is better than getting no vaccine at all.
Flu Shot Beats Flu Spray: Study Details
For the study, Monto and his colleagues enrolled 1,952 healthy men and
women, all aged 18 to 49, in the fall of 2007. They randomly assigned the
participants to receive either the traditional vaccine, the nasal spray, or
placebo, without the participants knowing if they were getting placebo or the
They tracked the participants throughout the 2007-2008 flu season, and
suspected cases of influenza -- marked by muscle aches, headache, nasal
congestion, nausea, and vomiting -- were confirmed either by cell culture of
the virus or by a highly sensitive test known as a PCR assay, or both.
Flu Shot Beats Flu Spray: Study Results
At the end of the study, 119 people had confirmed influenza. Those who got
the injection had a 50% reduced chance of getting influenza compared to the
group that got the nasal spray.
When the researchers looked only at the vaccines' effectiveness in
preventing influenza A, the more common flu to infect the participants, the
injection was 72% effective but the nasal spray just 29%.
Too few cases of influenza B were found to compare the vaccines, according
to Monto. Funding for the study was provided by the National Institute of
Allergy and Infectious Diseases and an unrestricted grant from Sanofi Pasteur,
which makes the flu shot vaccine. MedImmune provided the nasal spray vaccine.
Monto has received lecture fees from Sanofi Pasteur.
Flu Shot Beats Flu Spray: Study Implications
In recent years, studies comparing the two types of vaccines have produced
mixed results, Monto says. ''Definitive studies have been done in children
looking at the same comparison and they have found the live attenuated [nasal
flu spray] outperforms the inactivated, and that's for children under age
Why is that? ''The nasal spray vaccine works best in bodies which have
produced fewer antibodies," Monto speculates. The virus in the nasal spray is
attenuated, or weakened, and it must infect the nasal passages to trigger an
immune response, the production of antibodies, which protects against infection
by the virus.