Study: Flu shot better than nasal spray in adults

Sep 23, 2009

(PhysOrg.com) -- A flu shot is 50 percent more effective than nasal spray vaccine in preventing seasonal influenza in healthy adults, a new University of Michigan study shows.

The U-M School of Public Health study compared the effectiveness of a vaccine that uses an inactivated influenza virus with a vaccine that uses a live but weakened virus, said Arnold Monto, professor of epidemiology at the UM School of Public Health. The inactivated vaccine is delivered by injection, the live vaccine by nasal spray.

"This study now establishes that the flu shot is more effective than the nasal spray vaccines in healthy adults in preventing seasonal influenza," Monto said. The differences in protection were demonstrated for the A (H3N2) viruses, the seasonal strains which cause the most severe disease.

Both vaccines prevented influenza illnesses in the 2007-2008 season, but when comparing the vaccines against each other, the flu shot was 50 percent more effective than the nasal spray in preventing seasonal influenza, said Suzanne Ohmit, co-author of the study, which appears Sept. 24 in the New England Journal of Medicine.

The study was carried out in healthy adults between 18 and 49 years old. From the group's studies in previous flu seasons, the efficacy of the nasal spray vaccine in adults has been questioned. It is known that the nasal spray, or live virus vaccine, is likely superior to the inactivated vaccine for children, especially those under age 6, Monto said.

This could be because the virus in the nasal spray must infect the nasal passages in order to induce a protective immune response. Children have not been exposed to as many strains of the flu virus so they have not built antibodies to it and thus it's easier to infect their nasal passages with the weakened virus. Adults, on the other hand, might not become infected because they have build antibodies through past exposures and infection with influenza, he said.

It's important to note that this study does not address protection of either vaccine against the novel influenza H1N1 swine flu strain that has circulated since spring 2009. The strains used in both seasonal vaccines are different and won't protect against the novel H1N1 strain.

Because it's a novel strain, meaning most people have not been exposed to it, adults may respond well to a nasal spray vaccine for the swine flu virus, similar to the way that children respond to nasal spray for the seasonal flu. Both live and inactivated vaccines are currently being manufactured to prevent the novel H1N1 swine flu, Monto said, and should be used when available.

The paper, "Comparative Efficacy of Inactivated and Live Attenuated Influenza Vaccines," appears in the Sept. 24 issue of the New England Journal of Medicine.

The University of Michigan School of Public Health has been working to promote health and prevent disease since 1941, and is consistently ranked among the top five public health schools in the nation.

Provided by University of Michigan

Explore further: Diet affects men's and women's gut microbes differently

add to favorites email to friend print save as pdf

Related Stories

Flu season: How many shots?

Aug 30, 2009

(AP) -- Doctors don't know yet if it will take one dose or two of vaccine to protect against the new swine flu. Add that to vaccine for the regular winter flu, and it could be a multishot season for a lot of people - or ...

Ouch! Early flu shot season comes with 3 jabs

Aug 06, 2009

(AP) -- Get ready to roll up your sleeve three times for flu shots this fall. That's right, three times. This year's flu season is shaping up to be a very different one. Most people will need one shot for the regular seasonal ...

Recommended for you

Diet affects men's and women's gut microbes differently

10 hours ago

The microbes living in the guts of males and females react differently to diet, even when the diets are identical, according to a study by scientists from The University of Texas at Austin and six other institutions published ...

Researchers explore what happens when heart cells fail

11 hours ago

Through a grant from the United States-Israel Binational Science Foundation, Biomedical Engineering Associate Professor Naomi Chesler will embark upon a new collaborative research project to better understand ...

Stem cells from nerves form teeth

14 hours ago

Researchers at Karolinska Institutet in Sweden have discovered that stem cells inside the soft tissues of the tooth come from an unexpected source, namely nerves. These findings are now being published in the journal Nature and co ...

User comments : 0