Production for the coming flu season began last winter and spring, and drugmakers started shipping vaccines in midsummer.

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An egg shortage has driven up prices at the supermarket, caused in part by an outbreak of avian flu in the Midwest. But health officials say there is no need to worry about the supply of certain eggs outside the kitchen: the ones used to grow and incubate flu vaccine for humans.

Vaccine manufacturers get their eggs from chickens raised not in a typical coop but under heightened sanitary and biosafety measures.

“It’s a totally separate supply,” said Lynnette Brammer, an epidemiologist with the federal Centers for Disease Control and Prevention (CDC).

What’s more, production for the coming flu season began last winter and spring, as usual, and drugmakers started shipping vaccines to pharmacies and physicians in midsummer.

Sanofi Pasteur says it plans to ship more than 65 million doses to the U.S. market this flu season. GlaxoSmithKlein (GSK) says it expects to ship 32 million to 38 million doses.

While it’s too early to be certain, evidence suggests the vaccines could be a good match with the strains of flu that are expected to dominate this year, health experts say. That would be a switch from last year, when the vaccine was just 19 percent effective in preventing influenza-related medical visits, the CDC said.

In the Southern Hemisphere this year, where winter is drawing to a close, reports indicate a relatively mild flu season, said Neil Fishman, infectious-diseases physician at the Hospital of the University of Pennsylvania.

“That usually predicts a really mild influenza season in the Northern Hemisphere,” he said.

Flu vaccines come in various forms, and two words patients may hear at the doctor’s office increasingly are trivalent and quadrivalent.

Trivalent flu shots are designed to protect against two strains of influenza A and one of influenza B. Quadrivalent vaccines are meant to protect again two of each.

Federal officials have not recommended one over the other, though GSK, which sells the quadrivalent variety, says more variety offers broader protection. Sanofi also offers quadrivalent vaccines, and a high-dose trivalent version for senior citizens because the body’s immune defenses tend to weaken with age.

This year, the trivalent-versus-quadrivalent question may not matter, Fishman said. Most of the Southern Hemisphere cases of influenza B appear to match the strain used to make the trivalent vaccine, he said.

The CDC recommends a yearly flu vaccine for everyone 6 months and older, if possible by October, as it takes about two weeks after getting a shot for peak immunity to build.

Though the flu shot does not provide 100 percent protection, doctors say it is the best thing available.

Most people who get flu will recover on their own. But seniors and others who are more vulnerable should seek medical treatment.