Flu Shot Beats Nasal Spray Flu Vaccine?
Military Recruits Who Got Flu Shot Had Fewer Doctor’s Visits for Influenza, Study Finds
March 2, 2009 -- The traditional flu shot, given as an injection
in the arm, performs better than the newer nasal spray flu vaccine, shows a new study
that compared the two vaccines in military personnel.
"We did find both vaccines effective," says study researcher Angelia
Eick, PhD, a researcher at the Armed Forces Health Surveillance Center in
Silver Spring, Md. The study is published in the early online edition of The
Journal of the American Medical Association.
Because the study comparing the two vaccines was conducted among U.S.
military personnel, it's not possible to make recommendations to the general
population, Eick and co-researchers said at a telephone conference for
reporters. But the results may help experts one day recommend one form of the
flu vaccine over another.
Flu Vaccine Study: Details
Researchers compared the traditional influenza vaccine, first developed in
the 1940s, to the intranasal spray vaccine, available since 2003, to no immunization at all.
The nasal spray flu vaccine contains live but weakened flu virus and is
sprayed into the nostrils. It's approved for people aged 2 through 49 years.
The flu shot is an inactivated or killed virus vaccine.
The researchers looked at three flu seasons -- 2004 to 2005, 2005 to 2006,
and 2006 to 2007 -- and evaluated more than 3 million active-duty service
members stationed in the U.S.
"They were all less than 50 years old, with no contraindications to
vaccinate," says Zhong Wang, PhD, MPH, another study researcher and also a
researcher at the Armed Forces Health Surveillance Center.
"We looked for the first health care encounter following the vaccination
with a primary diagnosis code consistent with influenza or pneumonia," Wang says. That
was the measure of vaccine effectiveness.
Flu Vaccine Study: Results
Those who got the shot in the arm were less likely to visit the health care
system for influenza or pneumonia complaints, the researchers found.
Those who got the flu shot were 28% to 54% less likely to have a health care
encounter than the unimmunized group, Wang says, and those who got the nasal
spray flu vaccine were 10% to 21% less likely than the unimmunized group to
have a health care visit for flu or pneumonia. Those results cover all three
years, explaining the wide range, he says.
When they looked at vaccination history, the researchers found that the
nasal spray vaccine had an effect similar to the flu shot in those who had not
been vaccinated. That corresponds to some other study findings, the researchers
note, that in healthy adults who are regularly immunized, the shot works better
than the spray.
Flu Vaccine Study: Interpretations
"We need to keep in mind that this is one study," says Steven
Tobler, MD, MPH, another study researcher and also a researcher at the Armed
Forces Health Surveillance Center. "It certainly suggests that the
trivalent inactivated vaccine [the flu shot] in a young healthy population
might be more effective."
The study has limitations, Tobler says. For instance, the influenza cases
were estimated by the visits in which the doctor's diagnosis was influenza or
pneumonia, says Tobler, and the influenza cases were not confirmed in the