Breathe Easier: WHO Declares H1N1 'Swine Flu' Pandemic Over

The World Health Organization has declared the influenza H1N1 pandemic over. "The world is no longer in phase 6 of influenza pandemic alert," WHO director Margaret Chan said in a statement. "We are now moving into the post-pandemic period. The new H1N1 virus has largely run its course,"

"[T]his does not mean that the H1N1 virus has gone away," Chan added, explaining that the WHO now expects the virus to take on the behavior of a seasonal influenza virus and "continue to circulate for some years to come." Also, the WHO expects localized outbreaks of different magnitudes, as is the situation right now in New Zealand.

It is likely that the virus will continue to disproportionately affect a younger age group, at least in the immediate post-pandemic period, the WHO said. Those identified as being at high-risk of severe or fatal illness will probably remain at heightened risk -- though hopefully the number of such cases will diminish.

Interestingly, companies like Novartis (NVS), Sanofi-Aventis (SNY), AstraZeneca (AZN) and GlaxoSmithKline (GSK), which received a boost over the past year from the sale of pandemic flu vaccines, performed relatively well Tuesday, with NVS, AZN and GSK shares closing up some 1.5%. The companies and their investors realize that sales of the pandemic vaccine have largely completed.

Meanwhile, smaller vaccine plays, which already saw their shares decline as the pandemic eased, witnessed another drop Tuesday. Novavax (NVAX), which received thumbs up from some analysts saw its shares climb following several positive H1N1 vaccines trial results, saw its shares close down 1.3%. Likewise Vical (VICL), which also received a nice boost from vaccine sales, fell 3.2% Tuesday. Chinese vaccine manufacturer Sinovac (SVA) sank 1.1%, while BioCryst (BCRX), whose investigational antiviral drug peramivir received FDA authorization for emergency use last October, dropped 0.4%.

As of August 1, worldwide more than 214 countries, territories and communities have reported laboratory confirmed cases of pandemic influenza H1N1 2009, including over 18,449 deaths. This is much less than a typical flu season. The WHO responded to criticism it overreacted, launching several investigations. But Chan said "we have been aided by pure good luck."

The WHO and Chan have always maintained that "pandemics are unpredictable and prone to deliver surprises. No two pandemics are ever alike. This pandemic has turned out to be much more fortunate than what we feared a little over a year ago," Chan said. She added we were fortunate the virus did not mutate to a more lethal form and that widespread resistance to oseltamivir (Tamiflu) did not develop. Also, the vaccine proved to be a good match with an excellent safety profile, she said.