Flu vaccines go through a months-long process of development and approval before they reach patients' arms each fall. Photo by Carol E. Davis via Flickr under Creative Commons.
Story and Graphics by Jordan Humphreys
For Reporting Texas
Swab. Prick. Stick. Flu shots last only a few seconds but behind each shot is a year’s worth of planning, research and development.
New flu vaccines are distributed every August, but the vaccine is chosen eight months before by the World Health Organization, the health branch of the United Nations. WHO decides which three strains will be the most infectious during the upcoming flu season based on how they are spreading through the world. The organization then sends its recommendations (pdf) to each region, and the countries license companies to create vaccines to be shipped to clinics and doctors’ offices. The H1N1 strain chosen for this season’s North American virus composition is the same used in the 2009 flu pandemic vaccine.
In the United States, the Centers for Disease Control and Prevention released those strains to licensed companies to mass produce the vaccines, said Brad Bracken, a public health director for one company, Sanofi Pasteur.
“Our scientists follow what’s circulating where, and we start to produce vaccines well before the recommendations,” Bracken said. “We make four or five that we think the CDC will pick and produce them in bulk. If we’re right — and we have been so far — we’re way ahead of the curve.”
Sanofi Pasteur and other vaccine creators grow each of the three viruses in chicken eggs specifically bred for flu vaccines. Eggs have been used since flu vaccines were first mass-produced in the 1940s to protect World War II soldiers after a pandemic during the first world war, said Dr. Jeremy Franklin, director of medical sciences for MedImmune, another vaccine manufacturer.
Graphic by Jordan Humphreys.
“It takes a lot of eggs to grow these cells,” said Coleen Christian, immunization program coordinator for the Austin Travis County Health and Human Services. “This procedure uses millions and millions of chicken eggs each year.”
After a three-month incubation period, viruses are removed from the eggs, and their antigens are isolated and purified. These antigens build up a person’s immune system against the viruses but can’t actually cause the flu. The viruses in these vaccines are killed or so weakened that they can’t cause the flu.
The three strains of the vaccine are then combined and packaged into a shot or nasal mist. The shot contains the killed virus while the nasal mist contains a live, weakened version. “This results in better immune response because it mimics natural infection as a live virus much better than the killed virus,” said Franklin of MedImmune, which produces the FluMist vaccine.
Once the mists and shots are packaged by their companies, each batch is tested and approved by the Food and Drug Administration and then sent out to clinics and doctors’ offices in late summer.
The weakened virus is bred to live in about 77 degrees Fahrenheit, much colder temperatures than the lungs. For this reason, it’s unable to grow effectively and can’t infect people with healthy immune systems, but the body reacts as if it has the flu and bulks up its immune system.
The nasal mist vaccine is more effective for people with healthy immune systems. But pregnant women, children between 6 months and 2 years old, and those older than 50 should opt for flu shots, which officials say are still safe and effective. The vaccine, however, is not recommended for anyone with egg allergies.
About two weeks after getting a vaccine, the body is ready to fight off the flu. A person can stay immune for up to eight months. Each vaccine lasts one year before expiring, but Franklin says it is only useful to get a vaccine if it is still flu season.
“In some places people stop getting vaccines as early as Thanksgiving, but in other areas spikes in flu activity are in February and as late as April,” he said. “After April, flu activity is way down and it’s usually not useful to get a vaccine.”
The CDC suggests flu shots for all eligible people to keep families and communities healthy during flu season. Getting a flu vaccine is also more cost-effective because being hospitalized with the flu costs $13,000 on average, according to a CDC report.
Fewer people have made their way to clinics for shots this past flu season, and so a surplus of vaccine will need to be safely destroyed, said Christian of Austin Health and Human Services. Of the 147 million doses of the H1N1 vaccine made last year, 40 million shots and nasal mists expired and had to be sent back to manufactures to be destroyed, she said.
Right as old vaccines are expiring, new vaccines are being sent to clinics in July and August to continue the cycle, Franklin said.