Tue. Jan 18th, 2022

It’s November, which means for two months you’ve probably been bombarded with reminders that you should get a flu shot by signs at drugstores, organizations with tables on campus, flyers and emails. Maybe you’ve wondered why everyone thinks this is so important or how a flu shot is even made.

The flu virus is more than just a bad cold; it typically causes a fever, body aches, fatigue and headaches, in addition to a stuffy nose and cough. It can take from a few days to two weeks to recover from, barring the occurrence of complications such as sinus infections, ear infections or even pneumonia.

According to The Centers for Disease and Prevention federal agency (CDC), being vaccinated is the best method for preventing infection and can reduce the risk of being infected by 40 to 60 percent when the strains in the vaccine are well-matched to circulating strains.

The flu virus has many different strains and is constantly evolving. The flu shot contains three or four flu strains which are inactivated so they cannot cause infection but will still trigger your immune system to create antibodies that fight those strains. It takes about two weeks from the time you get a flu shot for antibodies to be produced, but once they are, your body is able to fend off a future attack by those strains and prevent you from developing symptoms.

The strains included in each year’s vaccine are selected based on data on flu infections collected by the The Food and Drug Administration (FDA). It takes a significant amount of time to create large batches of the flu vaccine, so the FDA must predict which strains will be prevalent in February, long before the flu season begins in the fall.

Once the FDA determines which flu strains are most likely to be prevalent, it informs vaccine manufacturers, who then begin producing material for the flu shot in one of three ways. The most common is an egg-based process which has been used for over 70 years.

In this process, the manufacturer is provided with samples of candidate vaccine viruses—the strains of the flu virus the FDA predicts will be prevalent—which have been grown in chicken eggs. The manufacturer injects these samples into other fertilized eggs and incubates them for several days while the virus multiplies.

After this, they extract the virus-containing fluid from the eggs, kill the virus and purify the fluid for use in the vaccine.

The second way vaccines can be produced is a cell-based process approved by the FDA in early 2012, with the process lasting until 2016. This process also began with samples of candidate vaccine viruses grown in eggs; however, instead of being injected into fertilized chicken eggs to replicate, these samples were injected into animal cells grown in a lab.

In August 2016 the FDA approved candidate vaccine virus samples which were initially produced in cells instead of eggs to be injected into more animal cells for virus replication, eliminating the use of eggs in the process.

The third way vaccines can be made is through recombinant technology. In this process, approved by the FDA in 2013, vaccine manufacturers isolate a particular protein known to provoke immune system response from naturally occurring candidate vaccine viruses and combined it with parts of another virus that grows well in insect cells. This combined, or recombinant, virus is injected into insect cells to replicate, and finally, fluid containing the virus is extracted and processed as in the other two methods.

Currently, the vast majority of manufacturers produce the flu shot using the egg-based process. The cell-based and recombinant processes are used by one manufacturer each, however, these newer processes have advantages which may change how we mass-produce flu vaccines in the future.

They are both faster than the egg-based process and neither relies on the availability of eggs. Additionally, early studies have shown flu vaccines made with viruses grown in cells instead of eggs may provide more effective protection.

Abbey Bigler is a fourth-year student majoring in English with minors in business and technical writing, communication studies and biology. She can be reached at AB842693@wcupa.edu.

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