Flu Vaccines

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 henhouse that met biosecurity requirements.

Sound complicated? It is. The manufacturing of flu vaccines is a highly-orchestrated and complex process.

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.

The Food and Drug Administration (FDA) and its parent, the U.S. Department of Health and Human Services, have long encouraged the development of new technologies for producing flu vaccines. For example, cell culture technology is used to make vaccines to prevent other infectious diseases, and FDA has been working for a number of years, both on the research and regulatory fronts, to facilitate this for flu vaccines. A major push for cell-based flu vaccines occurred in 2006 as part of a plan to be ready in case of a world-wide 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.