Getting your annual flu shot is the best way to lower your chances of getting sick with seasonal influenza. But not all flu vaccines are created equal. Major scientific advances over the past decade are making newer flu shots more effective at protecting against a broad range of influenza strains.
Recent innovations in how flu shots are produced and formulated are helping them keep pace with the ever-changing influenza virus. As a result, people who get vaccinated can head into flu season with confidence that their immune system is ready to fend off whatever flu strains may come their way.
How Do They Know What Flu Vaccine to Make
Every year medical experts face the massive challenge of predicting which particular influenza strains are likely to spread and cause the most illness over the upcoming winter. This involves a complex global surveillance program.
- The World Health Organization (WHO) has a network of National Influenza Centers in over 140 countries. These centers test thousands of influenza virus samples and report their findings.
- The U.S. CDC also has flu surveillance systems domestically. For example, clinical laboratories across the nation send in specimens for analysis at CDC labs.
- Data from Southern Hemisphere countries during their flu season, which occurs during our summer months, provides an early look at strains likely to circulate in the Northern Hemisphere too.
By taking all this surveillance data into account, scientists make their best forecast about which viral strains should be included in the annual flu vaccine for optimum protection. Typically they will recommend 3 or 4 strains that they expect to be the most widespread and virulent.
This surveillance and prediction work starts very early, since it takes months to manufacture hundreds of millions of flu shots for the Fall. The WHO makes its final influenza vaccine strain selections around February for the following winter in the Northern Hemisphere.
Then it’s a race for vaccine makers to tweak their formulations and ramp up production in time for flu season.
Does the Flu Vaccine Change Every Year
In a word – yes. The strains targeted by the flu shot have to change most years. This is because influenza viruses are continually evolving.
There are two key reasons the formulation must be adjusted annually:
- Viral Mutations: Flu viruses are masters at mutating and producing new strains and subtypes. As they replicate, random errors in their genetic code occur frequently. Most mutations have no effect, but some create versions different enough that prior immunity provides less protection.
- Lack of Prior Exposure: Especially for young people, each flu season may bring their first exposure to some viral subtypes. With no existing immunity, they remain vulnerable.
Both factors mean the immunity people have from vaccines or infections in previous years gradually becomes less effective. So public health experts have to make their best prediction about which mutated or new strains will be dominant in the upcoming flu season.
Then the vaccine strains are updated accordingly and people need to get the annual shot for optimal defense. Some years the predictions align closely with what actually circulates, while other years prove more mismatched if unexpected strains predominate.
How Are Annual Flu Vaccines Tested
Once manufacturers receive the WHO’s recommended strains for the Northern Hemisphere’s next flu vaccine, the race is on. First they use those viral strains to produce pilot lots of the new vaccine formulation.
These lots undergo extensive testing and clinical trials to assess:
- Safety: Monitoring for any adverse reactions or side effects.
- Immunogenicity: Measuring if the vaccine induces adequate antibodies against the target strains. Higher antibody levels signal the person’s immune system is primed to respond.
Manufacturers submit all this data to the U.S. Food & Drug Administration (FDA) as part of the annual approval process. The FDA determines if the new vaccine meets all requirements for safety, purity and potency.
Once the FDA signs off, mass production begins and doses start shipping to clinics, pharmacies and doctors’ offices. It’s a monumental undertaking to deliver over 170 million flu shots to Americans every fall.
Flu Vaccine FDA Approval Process
The FDA’s vaccine approval process ensures each year’s flu shots are effective and safe. Key steps include:
- Clinical Trial Review: Manufacturers submit data from clinical studies showing the new vaccine triggers a strong immune response (antibody levels) against that season’s viral strains. Adverse reactions are monitored closely as well.
- Manufacturing Inspection: The FDA inspects production facilities and processes. Samples from each vaccine lot are tested to guarantee quality and consistency.
- Label Review: Proposed packaging and prescribing information is evaluated to ensure it provides necessary usage guidelines, warnings and ingredient lists.
- Final Action: If requirements are satisfied across the board, the FDA issues the appropriate license for the updated formulation so distribution can proceed.
While this approval happens annually, flu shots use an efficient process that leverages cumulative safety and efficacy data rather than starting from scratch each time. But there’s still a tight timeline as the WHO recommendations are finalized only about 7 months before flu season starts.
Manufacturing Innovations Behind Better Flu Shots
Advances in how flu vaccines are made and formulated have accelerated in recent years. This is driven by the goal of effectively keeping up with influenza’s continual evolution. Here are some key innovations:
Cell-Based Vaccine Production
For decades flu shots have relied on chicken eggs in the manufacturing process. Fertilized eggs are injected with reference strains and the viruses replicate inside them.
But newer cell-based technology allows vaccine viruses to grow in mammal cells instead:
- Provides conditions more similar to those in the human body
- Gives tighter control and standardization of viral growth
- May enable a closer antigenic match to circulating strains
- Shots stimulate a stronger antibody response than egg-based versions
In 2020, about 60% of flu shots distributed in the U.S. were produced in cells rather than eggs.
Recombinant Technology
An even more high-tech approach is recombinant flu vaccines made without using influenza viruses at all. Instead, the critical hemagglutinin surface proteins of target strains are inserted into a harmless vector virus:
- The vector virus shells replicate quickly in insect cell cultures
- Hemagglutinin proteins are harvested from this growth process
- Then purified proteins are assembled into the final recombinant vaccine
Benefits of this fully synthetic technique include:
- Avoids reliance on chicken eggs
- Much faster startup and production compared to egg-based or cell-based methods
- Potential for recombinant vaccines to offer broader protection across strains
The technology is still relatively new but holds great promise for the future.
Quadrivalent Vaccines
Older seasonal flu shots contained protection against three influenza strains (trivalent). But quadrivalent vaccines include four strains:
- Two influenza A strains (H1N1 and H3N2)
- Two influenza B strains from different lineages (Yamagata and Victoria)
Adding another B strain aims to cover more potential variation circulating in a given season. However, it’s not always clear if that 4th strain will be prominent enough to improve effectiveness in practice.
More real-world experience over time will reveal if quadrivalent vaccines consistently outperform their trivalent predecessors. But the expanded coverage provides better odds as influenza continually reinvents itself.
FAQ’s
What Technologies Are Used To Make Flu Vaccines?
Flu vaccines are crafted using various technologies, including inactivated viruses, live attenuated viruses, and recombinant DNA technology.
How Was The Flu Vaccine Developed?
The flu vaccine is developed through a meticulous process involving surveillance, virus selection, cultivation, inactivation, and formulation to create effective immunization.
What Is The Recombinant Flu Vaccine Technology?
Recombinant flu vaccine technology involves using genetic engineering to produce viral proteins, creating a vaccine without the need for live viruses.
What Is The Technical Name For The Flu Shot?
The technical term for the flu shot is “Inactivated Influenza Vaccine”(IIV), as it contains killed influenza virus particles.
How Effective Is The Flu Vaccine?
The effectiveness of the flu vaccine varies each year but generally reduces the severity of illness and lowers the risk of complications, enhancing overall protection against influenza.
Conclusion
Seasonal flu shots remain the best line of defense during flu season each year. But influenza’s high mutation rate enables it to keep evading our immune defenses. New vaccine technologies are critical to keep pace.
Key innovations like cell-based and recombinant manufacturing, along with quadrivalent formulations, are already making flu shots more adaptable and higher performing. As these platforms mature and expand, they should translate into meaningfully better protection against both seasonal flu strains and potential future pandemics.
But realistically, the need to get updated annual flu shots is unlikely to go away anytime soon. Influenza viruses are just too unpredictable. Our best strategy is making sure the latest tools and scientific insights are deployed to maximum advantage in this ongoing arms race.
So be sure to get this season’s flu shot and take advantage of the substantial progress. While the flu virus keeps changing, our vaccines against it are getting better all the time.
