How are influenza (flu) vaccines made?

PIGS, PANDEMICS AND A BETTER VACCINE But even the most effectively formulated seasonal flu shot is, by design, only intended to protect people from the types of flu that commonly circulate

in humans. Among researchers, another main area of concern is the possibility of a flu pandemic, which occurs when a flu virus that typically infects animals, like pigs or birds, changes in

such a way that it can spread rapidly — and perhaps lethally — from person to person. That's where experts like veterinarian and professor Andrew Bowman, who leads Ohio State

University's animal influenza research program, come in. Bowman and his team spend each summer traveling to more than 100 county fairs, where they swab the snouts of exhibition pigs in

search of flu strains with pandemic potential. Much like the CDC researchers who analyze human flu specimens, their goal is to use genetic testing to get an early look at potentially

troublesome changes in the viruses they capture. "As we characterize these strains, we can identify viruses that might be able to spread human-to-human so that we can have effective

countermeasures in place before ... an outbreak,” Bowman says. These countermeasures include collaborating with the CDC to have the building blocks of a pandemic flu vaccine at the ready,

should the need arise. But it doesn't take a pandemic for the flu to be a serious, even fatal, health threat — especially for older adults. WHEN TO GET YOUR FLU SHOT It takes about two

weeks to build up immunity after receiving the flu shot, so experts say early vaccination is key: The CDC recommends getting the flu shot early in the fall, by the end of October. If

you're 65 or older, ask your doctor about the high-dose or adjuvanted version of the vaccine, which is formulated specifically for older adults. chokkicx/Getty Images "The typical

patient that gets complications from the flu is usually an older person, and usually somebody with an underlying medical condition,” says emergency physician Jeremy Brown, author of 

_Influenza: The Hundred-Year Hunt to Cure the Deadliest Disease in History_. According to the CDC, an estimated 90 percent of flu-related deaths and 50 to 70 percent of all hospitalizations

for flu occur among people age 65 and older. While the effectiveness of the flu shot varies from year to year, the agency estimates that it prevents millions of cases of flu and flu-related

doctor visits annually. Still, Brown notes, there is room for improvement. Typically, the flu shot is about 50 percent effective, but that rate has dipped as low as 19 percent in recent

years. In those cases, he says, low rates might be the result of a vaccine formula that isn't well matched to the viruses that end up going around, despite the experts’ best prediction.

They might also be caused by a vaccine that, although well matched, just doesn't stimulate our immune systems like it should. One hope, he says, is that a universal flu vaccine that

protects against all possible strains of the virus could someday replace the yearly shot entirely. But despite early trials, he says the prospect is still a long way off. In the meantime,

the flu virus continues to change, evolving in ways both expected and unforeseen. The expert advice, on the other hand, remains the same: Get the flu shot. Your future self might thank you.