New Flu Vaccines Helps People Allergic to Eggs

The flu vaccine that you get at your doctor's office or pharmacy is the work of highly skilled microbiologists, epidemiologists, physicians and other public health experts too numerous to mention. It also likely required a hen and a rooster monitored by a veterinarian inside a hen house that met biosecurity requirements.

Vaccine manufacturers each year use millions of fertilized eggs as a culture to grow influenza viruses that, after numerous steps requiring about six months of expert work, become that season's flu vaccine. And while this tried-and-true method will continue to provide safe and effective vaccines for the foreseeable future, flu vaccines using new, more advanced technologies are arriving on the scene. Some don't require eggs at all.

. A major push for cell-based flu vaccines occurred in 2006 as part of a plan to be ready in case of a worldwide epidemic.

In 2010, FDA issued final guidance to assist manufacturers working to develop safe and effective viral vaccines that grow in specially prepared cell lines. In the last two months, FDA has approved two new flu vaccines that, instead of using eggs to grow the influenza virus, use cell lines from either a mammal or insects.

"This is an important advance that will supplement current egg-based vaccines," said Jerry P. Weir, Ph.D., director of the Division of Viral Products in FDA's Center for Biologics Evaluation and Research. "The more manufacturing alternatives there are available, the better we can respond to public health emergencies in a timely manner."

Although egg-based production remains vital, cell technology has some advantages. Unlike eggs, cells can be frozen for later use to grow large volumes of cells. That advantage offers the potential for faster start-up of the vaccine manufacturing process for any unexpected need. This would also be critical if egg supplies were compromised. In addition, some flu virus strains don't grow that well in eggs at first and may grow better and faster in cells, helping speed vaccine production and availability. Moreover, alternatives to egg-based products provide an option for people with egg allergies.

The first flu vaccine to use cell-based rather than egg-based technologies, Flucelvax, was approved by FDA in November 2012 for use in people ages 18 and older. The manufacturing process for Flucelvax is similar to the egg-based production method, but the virus strains included in the vaccine are grown in cells of mammalian origin instead of eggs.

A second flu vaccine that is manufactured using another new technology was approved on January 16, 2013 for use in people 18 through 49 years of age. Called Flublok, it does not require the use of actual influenza viruses and eggs are not used at any point in the manufacturing process.

Flublok uses an influenza virus protein that is made by genetically modifying a virus that infects insect cells to produce the flu vaccine protein. The protein, as in other flu vaccines, then triggers the immune system of the person receiving the vaccine to make protective antibodies.

Similar technology, Weir noted, has been used successfully before in other licensed vaccines, such as the vaccines used to prevent cervical cancer. Finding a safe and effective way to use the technology to prevent influenza "represents a breakthrough," said Weir. "It provides another important option to fight a disease associated with the deaths of thousands in the United States every year."