All commercially available flu vaccines in the United States are made by private sector manufacturers. Different manufacturers use different production technologies, but all flu vaccines meet FDA safety and efficacy requirements. The different vaccines are approved with different indications.
By Jon Cohen Sep. Those antibodies ideally prevent HA from attaching to cellular receptors, thwarting infection. But those studies relied on a misleading methodology. Without a simple way to detect the virus in the blood, researchers measured antibody levels, looking for a spike that occurs after infection.
Then in the s, sensitive polymerase chain reaction tests enabled researchers to actually measure viral levels, and they told a different story. It turned out that some people who did not have the big antibody spike after exposure—and were therefore counted as a vaccine success—actually did show a jump in viral levels, signaling infection.
Earlier assessments had exaggerated vaccine efficacy. Something else was afoot. Loss of confidence For decades, tests suggested the flu vaccine worked extremely well, but in the past 15 years a better test revealed many infections in vaccinated people who would previously have been deemed protected.
In a preprint published 15 August on bioRxiv, his team reports sequencing influenza DNA from viral specimens collected from people over five influenza seasons. They found loads of HA mutations, as expected, but most weakened the virus, making it "unfit," meaning it could not transmit human to human.
Viable escape mutants, Monto concludes, are too rare to explain the failures seen year after year. The most common influenza vaccine contains an "inactivated" virus, which manufacturers grow in chicken eggs.
He has preliminary evidence that egg-adapted mutations were behind the weak protection seen with the vaccine used in the —17 season, he says. He also points to a recent study by another group that compared an egg-grown vaccine with one that contained genetically engineered HA, which sidesteps the mutation issue.
The engineered vaccine offered more solid protection. That suggests a way to improve current vaccines, Hensley says.
Vaccinemakers largely rely on an old technique that exposes ferrets—which differ from humans—to candidate vaccine strains and then assesses whether they can stop viral isolates from people naturally infected with the circulating strains. Genetic comparisons, he says, would yield a better match.
Understanding the immune responses that correlate with protection could also help refine vaccines. Further complicating the picture is the immunologic legacy of multiple exposures to influenza each year—from the vaccine and from wild-type virus.
This may explain why middle-aged people in —14 were unusually hard-hit by a viral mutant that did not infect most vaccinated people, his team has reported. Immunologist Rafi Ahmed at Emory University in Atlanta last year reported that long-lived memory B cells to flu, which produce antibodies, can crowd out B cells that would otherwise respond to novel infections.Why do I need a flu vaccine every year?
A flu vaccine is needed every season for two reasons.
First, the body’s immune response from vaccination declines over time, so an annual vaccine is needed for optimal protection. More information about the safety of flu vaccines is available at Influenza Vaccine Safety. Flu vaccine is produced. Most vaccines are rarely changed but new flu vaccines are produced every year.
Why are flu shots constantly being reformulated? Certain parts of the viral genome are reshuffled by . How is the influenza vaccine produced, and why are new vaccines produced every year?
o The vaccine production starts about 9 months before it even becomes available to the public. Every year, to protect the U.S. population, the Centers for Disease Control and Prevention (CDC) evaluates which strains of flu virus are predominant in the United States and, if necessary, changes the vaccine recipe.
The accuracy of the recipe determines how effective that year's vaccine will be. Every year, the World Health Organization predicts which strains of the virus are most likely to be circulating in the next year (see Historical annual reformulations of the influenza vaccine), allowing pharmaceutical companies to develop vaccines that will provide the best immunity against these strains.
The job of producing a new vaccine for the next flu season starts well before the current flu season ends.
For FDA, it's a year-round initiative. The composition of vaccines for other diseases can stay the same year after year. But because influenza viruses are constantly evolving, and the viruses that circulate among people often change from .