Pandemic strain 2009 H1N1

This study addresses the seasonal influenza and not the protection of either vaccine against the novel influenza H1N1 swine flu strain that has circulated since spring of 2009.  The strains used in both seasonal vaccines are different and won’t protect against the novel H1N1 strain.

A new University of Michigan School of Public Health study shows that a flu shot is 50 percent more effective than nasal spray vaccine in preventing seasonal influenza in healthy adults!  The differences in protection were demonstrated for the A (H3N2) viruses, the seasonal strains which cause the most severe disease.

The 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 S. Monto, M.D., professor of epidemiology at the University of Michigan School of Public Health. The inactivated vaccine is delivered by injection, the live vaccine by nasal sprayflu-injection Suzanne E. Ohmit, Dr. P.H. and co-author of the study stated that both vaccines prevented influenza illnesses in the 2007-2008 seasons, but when comparing the vaccines against each other, the flu shot was 50 percent more effective than the nasal spray in preventing seasonal influenza in healthy adults.

1,952  Healthy adults between 18 and 49 years old participated in the group study and the new test results confirmed the results of group’s studies from previous flu seasons as to the effectiveness of the nasal spray in healthy adults. The flu shot was 68 percent successful at preventing the flu compared with the nasal spray, which was 36 percent effective, the researchers reported.

Among young children, live attenuated vaccine had significantly better efficacy than inactivated vaccine. An evaluation of the risks and benefits indicates that live attenuated vaccine should be a highly effective, safe vaccine for children 12 to 59 months of age who do not have a history of asthma or wheezing according to clinical trials performed by the National Institutes of Health (NIH).

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 Professor Arnold Monto reveals.

Concerning the novel influenza H1N1 swine flu strain that has circulated since spring of 2009, 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, Professor Monto points out and should be used when available and you can check on the availability of flu vaccine on the  Department of Health and Human Service website

As far as the seasonal influenza is concerned however, it may be better to roll up the sleeves and get a jab in the arm instead of a squirt in the nose.