With Swine Flu On The Wane, Health Officials Look Ahead

As the first influenza pandemic of this century appears to have turned a corner, preparations are already under way for next flu season.

Today the World Health Organization picked the strains to go in next fall's Northern Hemisphere flu vaccine. The ingredients: the pandemic H1N1, or swine flu, virus that now predominates almost everywhere, an H3N2 that's circulating in parts of Asia, and an influenza-B virus now causing most Chinese flu.

Next Monday the Food and Drug Administration is expected to follow suit.

 

On Tuesday, WHO is convening its Emergency Advisory Committee to ponder if the world has entered a "post-peak period" of the pandemic. "We hope the worst is behind us and that the overall trend will be going down," said Dr. Keiji Fukuda, WHO's chief flu official.

For more on these developments, listen to a conversation I had with Linda Wertheimer on Thursday's Morning Edition.

The numbers indicate the peak has passed. There's a diminishing chance of a "third wave" of flu following on the upsurges of last spring and fall. In North America, the pandemic peaked in mid-October—before much pandemic flu vaccine was available. The curve's been pretty much downhill since December.

And how bad has this pandemic been? Not nearly as wicked as many feared. New numbers from the Centers for Disease Control and Prevention tell an interesting story. Between April and January, about 57 million Americans got the new flu. That 19 percent "attack rate" is about the same as a severe flu season. Hospitalizations from flu? About the same as a typical flu season, may be a little more—257,000 is the CDC's middle estimate.

But when it comes to flu deaths, it's a different story. CDC customarily says about 36,000 people die of flu-related causes in a typical season. But over the past 10 months of pandemic flu, the agency has counted about 12,000 deaths.

The most striking difference is who got seriously ill from pandemic flu, and who died. Normally people over 65 make up the majority of flu hospitalizations and 90 percent of deaths.

But the CDC says over the past 10 months, nine out of 10 hospitalizations were among Americans under 65. And nine of out 10 deaths were also among younger adults and children.

Will the same pattern hold next fall? A third or more of the US population is already immune to the pandemic virus, at least in its current version. That's because they've either had the flu or are among the 75 million Americans who've been vaccinated against it.

"What that will mean in terms of disease patterns in the fall, I don't think any of us really knows," says the CDC's Dr. Beth Bell.

But the WHO's Fukuda says, "It would be very surprising if we were to see a very abrupt change in who is at risk from this virus." He also points out that the swine flu virus "more directly affects cells in lung, and people more often develop viral pneumonia, a very severe complication we see much less often with seasonal flu viruses."

So it would be a mistake to assume that the swine flu virus, as it transitions to a regular seasonal flu virus, poses no more risk. And two-thirds of Americans are still vulnerable to swine flu. That still gives the new virus plenty of opportunities.

One silver lining: US officials hope some of the 74 million doses of leftover pandemic flu vaccine that's sitting in manufacturers' freezers can be used for next fall's vaccine. That would give the nation a big jump in making next fall's vaccine. Which could mean earlier access to flu shots.

The trick, as always, is persuading people they need to get vaccinated.