NEPA Vital Signs - Winter Spring 2018 - 11

WINTER/ SPRING 2018

Feature
influenza centers worldwide conduct year-round surveillance on
the influenza illness. The World Health Organization (WHO) then
reviews the results of surveillance, laboratory, and clinical studies
to make recommendations on the composition of the flu vaccine
for the upcoming year. In the United States, it is the Food and Drug
Administration (FDA) that makes the final decision about vaccine
viruses for the influenza vaccine to be sold in the U.S.

Although determining how well a
flu vaccine works is challenging,
recent studies suggest that the flu
vaccination reduces the risks of
flu illnesses by 40-60%.

Once the three or four virus strains are selected for the
upcoming flu season, the vaccines are made most commonly
using an egg-based manufacturing process. Egg-based vaccines
are used to make both the flu shot and nasal spray. Candidate
vaccine viruses (CVVs), which are influenza viruses prepared by
the CDC or another public health partner that can be used by
vaccine manufacturers, are injected into fertilized hen's eggs and
incubated for several days to allow the virus to replicate. After
incubation, the virus-containing fluid is collected. For the flu
shots, the viruses are inactivated (killed) and the virus antigen
(the substance that causes an immune response in the body)
is purified. For the attenuated nasal spray vaccine, the starting
CVVs are weakened viruses and go through a different production
process. Finally, the FDA tests and approves vaccines prior to
release and shipment.

On the other hand, if the viruses are not closely matched, the
vaccine effectiveness can be reduced. However, even when the
viruses are not closely matched, the vaccine can still protect many
people and prevent flu-related complications. This protection is
possible because antibodies (proteins recruited by the immune
system to neutralize foreign antigens) made in response to the
vaccine can provide some protection against different but related
influenza viruses (called cross-protection).
Each season, researchers try to determine how well flu vaccines work as a public health intervention using randomized and
observational studies. In randomized studies, the flu vaccination
is randomly assigned, and the number of people who get the flu
in the vaccinated group is compared to the number that get the
flu in the unvaccinated group. In observational studies, the occurrence of the flu illness in vaccinated people is compared to the
occurrence in unvaccinated people. Although determining how
well a flu vaccine works is challenging, recent studies suggest that
the flu vaccination reduces the risks of flu illnesses by 40-60%.

Unfortunately, the flu vaccine is
only able to protect against the
three or four influenza viruses
that research indicates are most
likely to spread and cause illness
during the upcoming flu season.

It's true that the flu vaccination is not a fool-proof method for
avoiding the fever, aches, cough, congestion, and other symptoms
that come along with the illness. However, it has been proven
to provide some protection against the infection - and some is
better than none, right?

How well the flu vaccine works can range widely from season
to season. The two main factors that play a role in determining
the likelihood that the vaccine will protect a person from the
illness include the characteristics of the person being vaccinated, such as their age and health, and the match between the flu
viruses that the vaccine is designed to protect against and the
viruses that are spreading in the community. If the viruses in
the vaccine are closely matched to the circulating viruses, there
can be substantial benefits in terms of preventing flu illnesses.

GINA BAIAMONTE is a second-year medical student at Geisinger
Commonwealth School of Medicine. She graduated from Misericordia
University in 2016 with a B.S. in Biochemistry and hopes to pursue a
career in a surgical field.

Vaccine Effectiveness - How Well Does the Flu Vaccine Work. https://www.cdc.gov/flu/about/qa/vaccineeffect.htm
How Influenza (Flu) Vaccines are Made. https://www.cdc.gov/flu/protect/vaccine/how-fluvaccine-made.htm

N E PA

VITAL SIGNS

https://www.cdc.gov/flu/about/qa/vaccineeffect.htm https://www.cdc.gov/flu/protect/vaccine/how-fluvaccine-made.htm

NEPA Vital Signs - Winter Spring 2018

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