TIME

This Flu Shot Is Not Like the Others

Some people may get a new flu shot that’s made with dog cells instead of chicken eggs

This year Novartis shipped its first full batch of Flucelvax, a new vaccine that was only approved by the Food and Drug Administration in 2012. The company made a limited amount of the shot last year, but there are more doses to go around this flu season. And for the first time, the doses were made at the company’s newly approved U.S. plant in Holly Springs, North Carolina.

The vaccine is made without growing the influenza virus in chicken eggs, which is the way that flu shots were made for more than four decades. Instead, Flucelvax is grown in kidney cells from dogs. The technology means that the shot can be made in less time than a traditional flu shot—enough virus can be churned out in about 65 hours to 75 hours, compared to the six months or so it takes to grow in chicken eggs. It also means that people who are allergic to eggs now have another option for getting immunized against the flu.

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In studies that the FDA reviewed before approving the vaccine, the shot was 84% effective in preventing flu among adults who were vaccinated compared to those who received a placebo. People getting Flucelvax produced around the same amount of antibodies to the influenza virus as those who were immunized with a chicken egg-based flu vaccine.

Using animal cells instead of chicken eggs, say Novartis officials, allows them to have more control over the purity of the final vaccine. How well influenza grows in the chicken eggs is variable—some eggs or batches of eggs help the virus grow, while others aren’t as conducive to producing large amounts of influenza.

The cell-based technology is also a plus during a flu pandemic, since the platform can produce more doses quickly to control an outbreak as a particular influenza virus spreads among a population. The kidney cells are frozen and can be thawed quickly to begin growing virus. The company has produced doses of pandemic flu vaccine against H5N1 using the cell technology, and it’s keeping them in deep freeze as part of the U.S. government stockpile in the event of a pandemic.

The FDA has approved seven different types of flu shots—in addition to Flucelvax and the standard vaccine made from chicken eggs that protects against three strains of influenza, there is also a shot that protects against four strains of flu; for the needle-phobic, one with a microneedle injects just into the skin and doesn’t penetrate into the muscle, making it less painful; for the elderly who need more protection, there is a high-dose vaccine; for younger children there is a nasal spray; and for those allergic to eggs, there’s a shot made from bits of influenza proteins grown in insect cells. Not every doctor’s office or clinic carries every shot, so if you prefer one over the others, call your health care provider to find out if it will be available.

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