# 3177
Declan Butler, who writes for Nature, is a name well known in the flu world due to his excellent, and early coverage of the H5N1 avian flu virus.
Today Declan has an excellent overview of the current global vaccine manufacturing situation, and the debate over producing a live attenuated virus vaccine, instead of the traditional inactivated virus formulation.
First the article (which is excellent), then a little added value.
Vaccine decisions loom for new flu strain
Published online 12 May 2009 | Nature | doi:10.1038/459144a
World Health Organization considers live attenuated vaccines for swine-associated H1N1 outbreak.
Faced with the prospect of an influenza pandemic, the World Health Organization (WHO) is weighing up its options for advising manufacturers and governments on developing vaccines. With current manufacturing capabilities, there will be enough vaccine for only a fraction of the world's population, and not before six months from now. And most of that will go to rich countries.
Experts are meeting at the WHO on 14 May to discuss options for proceeding with a vaccine for the currently circulating swine-associated H1N1 strain. One controversial idea being floated is to use a live attenuated vaccine, which could boost the number of doses available from existing plants by 50- to 100-fold.
Manufacturers are lukewarm to the idea. The ordinary seasonal flu vaccine uses inactivated virus, and serious regulatory barriers exist to introducing a live-virus vaccine. Demonstrating efficacy and getting regulatory approval in time would pose "quite significant difficulties", says George Kemble, vice-president of vaccine research and development at MedImmune in Gaithersburg, Maryland, which makes live flu- virus vaccine.
LAIV (Live Attenuated Influenza Vaccines) are attractive, particularly when the world needs a huge quantity of easily to dispense vaccines in a hurry, because they can be produced in much larger quantities than Inactivated vaccines and can be delivered to the patient via a nasal spray.
There are questions, however, over their effectiveness. Particularly in adults.
In early March of this year we saw a report in JAMA (Journal of the American Medical Association) on a multi-year study done in the military comparing the relative effectiveness of LAIV with the standard TIV (Trivalent Inactivated Vaccine).
Zhong Wang, PhD, MPH; Steven Tobler, MD, MPH; Jean Roayaei, PhD; Angelia Eick, PhD, ScM
JAMA. 2009;301(9):(doi:10.1001/jama.2009.265).
The study compared the incidence of `influenza' and pneumonia among more than 1 million military personnel over the 2004-2005, 2005-2006, and 2006-2007 influenza seasons.
Military personnel receive either the TIV (trivalent inactivated vaccine) - the flu shot most people are familiar with - or the LAIV (live attenuated influenza vaccine) via a nasal spray.
By looking back at who got which type of vaccine (shot or nasal spray), and who was subsequently treated for influenza-like-illnesses or pneumonia, researchers conclude that the standard flu shot (TIV) is more effective in adults than the nasal spray (LAIV), particularly among adults that have received immunizations in the past.
None of this is to say that LAIV vaccines don’t protect the recipient. It is a matter of degree, and appears to depend on a number of factors, including the recipient's age, and vaccination history.
LAIV vaccines, like FluMist (tm) were developed primarily for children, and in that age cohort are believed to be more effective than the traditional shot.
Increasingly, young adults have gravitated towards the nasal spray vaccine because it is easier, and it avoids a needle. The level of protection in that age group, according to this study, is less than with the conventional flu shot.
After reviewing military vaccination records of over 1 million recruits, researchers found those that received the traditional TIV shot saw a reduction in doctor visits for flu-like symptoms of up to 54%.
Those who received the LAIV nasal vaccine only saw a reduction of 21%.
Whether that reduction in protection would carry over to a novel virus LAIV vaccine is unknown.
LAIV vaccines are approved, in the United States, for adolescents and adults 2 to 49 years of age.
It is believed that the older a recipient is, the more flu viruses they have been exposed to, which enables their immune system to kill off an LAIV vaccine before it can produce immunity.
Since the A/H1N1 is a novel virus, one that most people have little or no immunity to, it isn’t clear whether previous exposures to other circulating influenza viruses would negatively affect an LAIV’s effectiveness.
Again, more questions than answers as the world searches for ways to rapidly produce a safe and effective pandemic vaccine.
