Why isn't there a cure-all influenza vaccine?

Previously published Slate articles made new.
April 27 2009 3:25 PM

Why Isn't There a Cure-All Influenza Vaccine?

Because it wouldn't be safe.

Click here to read more from Slate on the swine flu. 

Strains of swine flu have been confirmed in the United States, Mexico, and Canada, prompting the United States to declare a public health emergency. The particularly virulent strain is believed to have caused the deaths of up to 103 people in Mexico and infected more than 1,000, causing heightened concern about a potential epidemic in countries around the world. In an "Explainer" published last winter, Michelle Tsai explained why they don't cram every strain of influenza into our yearly flu shots. The column is reprinted below.

The flu shot protects against only 40 percent of this year's viruses, the Centers for Disease Control said last week. On Thursday, the FDA decided to replace all three of the vaccine's influenza strains for next winter. Wait, why can't the scientists put every strain there is into the vaccine?

It wouldn't be worth the effort, even if it were feasible. There are thousands of influenza subtypes infecting people around the world, but very few are likely to make someone in the United States sick. Vaccinating people against a disease they're never going to get is a risky proposition: We don't know how the body would respond to a barrage of flu vaccinations. The patient might also develop a strong immune response to an insignificant strain, while skimping on antibodies for a nastier virus.

That's not to say that we're better off putting just three strains of influenza in a vaccine. Five or six might offer better protection than what we have today without running afoul of the problems described above. But there are other reasons not to cram more into the flu shot: For each added strain, you need about 15 micrograms of protein, so a diverse vaccine yields a larger dose. This means it might hurt more when you get a flu shot, or you might need to get multiple shots. People could also suffer greater side effects and allergic reactions. Some scientists are investigating universal flu vaccines, which work in a different way; the new shots under development target proteins that don't change much between different strains, meaning a single vaccine could protect against many strains.

In the meantime, there's the matter of manufacturing the extra strains. Pharmaceutical companies already have their hands full developing vaccines for just three forms in the United States. (Just four years ago, a national shortage forced government officials to discourage Americans from getting shots unless they were sick, infants, or elderly.) To make a single vaccine dose for a given strain, the virus must be injected into a chicken embryo; to manufacture enough doses for the whole country can take half a year. But the drug companies don't have enough eggs to make vaccines for 20 distinct viruses, let alone thousands. (There's reason for hope, however. By using bacteria, yeast, or mammalian cells to incubate viruses, scientists may be able to speed up production significantly.)

Developers would also need to undergo a lengthy process to show their new product is safe. Even if it did get approval in time for flu season, manufacturing costs would be much higher. That could make the flu shots more expensive for patients and result in fewer doses being administered.

Got a question about today's news? Ask the Explainer.

AP video: Obama addresses the swine flu outbreak.


Medical Examiner

The Most Terrifying Thing About Ebola 

The disease threatens humanity by preying on humanity.

I Bought the Huge iPhone. I’m Already Thinking of Returning It.

Scotland Is Just the Beginning. Expect More Political Earthquakes in Europe.

Students Aren’t Going to College Football Games as Much Anymore

And schools are getting worried.

Global Marches Demand Action on Climate Change


Blacks Don’t Have a Corporal Punishment Problem

Americans do. But when blacks exhibit the same behaviors as others, it becomes part of a greater black pathology. 

Why a Sketch of Chelsea Manning Is Stirring Up Controversy

How Worried Should Poland, the Baltic States, and Georgia Be About a Russian Invasion?

  News & Politics
Sept. 20 2014 11:13 AM -30-
Business Insider
Sept. 20 2014 6:30 AM The Man Making Bill Gates Richer
Sept. 20 2014 7:27 AM How Do Plants Grow Aboard the International Space Station?
  Double X
The XX Factor
Sept. 19 2014 4:58 PM Steubenville Gets the Lifetime Treatment (And a Cheerleader Erupts Into Flames)
  Slate Plus
Tv Club
Sept. 21 2014 1:15 PM The Slate Doctor Who Podcast: Episode 5  A spoiler-filled discussion of "Time Heist."
Sept. 21 2014 9:00 PM Attractive People Being Funny While Doing Amusing and Sometimes Romantic Things Don’t dismiss it. Friends was a truly great show.
Future Tense
Sept. 19 2014 6:31 PM The One Big Problem With the Enormous New iPhone
  Health & Science
Bad Astronomy
Sept. 21 2014 8:00 AM An Astronaut’s Guided Video Tour of Earth
Sports Nut
Sept. 18 2014 11:42 AM Grandmaster Clash One of the most amazing feats in chess history just happened, and no one noticed.