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How do vaccines work?

Vaccines work by tricking your body into thinking that it has been infected by a pathogen. This causes your immune system to build up a defense against them.

A vaccine is an imposter of one part of a pathogen.

Your immune system creates WBCs and antibodies to this part of a pathogen.

Thus, if you ever do get exposed to this pathogen, you already have WBCs and antibodies there to immediately attack it.

How are vaccines made?

The US CDC and other labs partner with the World Health Organization (WHO) to choose certain virus strains to send to private vaccine manufacturers.

The flu can mutate and strains can change each year, meaning new vaccines are needed for every flu season.

The selected virus is injected into a fertilized hen’s eggs, where it incubates and replicates for a few days — just as it would do inside a human host.

Scientists then harvest fluid containing the virus from the egg.

They inactivate the virus so it can no longer cause disease, and purify it, leaving scientists with the virus antigen.

The antigen is the crucial element — it’s a substance released by the virus that triggers your immune system to respond. That’s how the vaccine prepares your immune system for a real infection.

The entire process, from the arrival of the egg to the publicly available vaccine, takes at least six months, according to the CDC.

flu vaccine chicken eggs

Graphic by Jason Kwok, CNN article, with info from US CDC

Ssource: The US keeps millions of chickens in secret farms to make flu vaccines. But their eggs won’t work for coronavirus, Jessie Yeung, CNN, 3/29/2020. Graphic by Jason Kwok, CNN article, with info from US CDC


If vaccines contain parts of a pathogen, can we get sick from it?

Absolutely not. Consider this car shown bellow. It is made of hundreds of pieces, all of them working together. The car’s axles are labeled.

Imagine taking the axle out of a car, and putting it in your driveway. Could this axle, by itself, drive you anywhere? Of course not.

This is also how vaccines work. There’s no way that a single part can infect you.

car = virus

axle = antigen

drive-train-transmission xpertechautorepair

So why then do vaccines sometimes make us sick?

Answer: They don’t. That’s an urban myth.

Vaccines merely stimulate our immune system, which temporarily creates non-specific responses. For example, redness, swelling, small increase in body temperature.

These are not a sign of infection. Rather, they are the normal signs that your body is developing defenses against the antigen.

How effective are vaccines?

See these resources.

Vaccination greatly reduces disease, disability, death and inequity worldwide. World Health Organization

The science is clear: Vaccines are safe, effective, and do not cause autism. John Hopkins University.




How effective is the influenza vaccine?

The “flu” is short for “influenza virus”. How effective are influenza vaccines?

No one claims that vaccines are 100% effective. No medical technique is 100% effective. Most vaccines are very effective, usually over 90% effective.

However, that is not yet the case for flu vaccines. The flu virus evolves through natural selection, like all viruses and life, and it happens to evolve very quickly.

“CDC conducts studies each year to determine how well the influenza (flu) vaccine protects against flu illness. While vaccine effectiveness can vary, recent studies show that flu vaccination reduces the risk of flu illness by between 40% and 60% among the overall population during seasons when most circulating flu viruses are well-matched to the flu vaccine. In general, current flu vaccines tend to work better against influenza B and influenza A(H1N1) viruses and offer lower protection against influenza A(H3N2) viruses.”

Vaccine Effectiveness – How Well Does the Flu Vaccine Work? CDC (Centers for Disease Control)

So if it isn’t perfect, why use this vaccine at all?

Excerpted from the CDC article:

Keeps you from getting sick with flu.

Reduces risk of flu-associated hospitalization, including among children and older adults.

Flu vaccination lowers rates of some cardiac (heart) events among people with heart disease

Reduces chances of being hospitalized among people with diabetes (79%) and chronic lung disease (52%).

Helps protect women during and after pregnancy. Getting vaccinated can also protect a baby after birth from flu. (Mom passes antibodies onto the developing baby during her pregnancy.)

Vaccination reduced the risk of flu-associated acute respiratory infection by about one half

Significantly reduces a child’s risk of dying from influenza.

It can make your illness milder even if you do get sick.

Most importantly, it protects people around you, including those who are more vulnerable to serious flu illness, like babies and young children, older people.


Should we vaccinate children?

Yes. Don’t be manipulated by misleading social media memes.

Kids crying anti-vaccine meme

Oh, and there is more. See 34 Hilarious Photos of Kids Losing It Over NOTHING

Vaccine meme No-child

Aren’t vaccines a scam to make money?

Some people against vaccines claim that since vaccines cost a small amount of money, one is supporting “big pharma” (phramaceutical industry).

Therefore, they claim, one must not vaccinate their children.

Yet in reality, children who are not vaccinated may become very sick, and require expensive bills to treat them, if they even live.

The reality is the opposite of the conspiracy theory.

anti-vaccine movement meme

Related topics

Herd immunity


Learning Standards

Massachusetts Comprehensive Health Curriculum Framework

Students will gain the knowledge and skills to select a diet that supports
health and reduces the risk of illness and future chronic diseases. PreK–12 Standard 4
8.1 Describe how the body fights germs and disease naturally and with medicines and
8.2 Identify the common symptoms of illness and recognize that being responsible for individual health means alerting caretakers to any symptoms of illness.
8.5 Identify ways individuals can reduce risk factors related to communicable and chronic diseases
8.6 Describe the importance of early detection in preventing the progression of disease.
8.7 Explain the need to follow prescribed health care procedures given by parents and health care providers.
8.8 Describe how to demonstrate safe care and concern toward ill and disabled persons in the family, school, and community.
8.13 Explain how the immune system functions to prevent and combat disease

Interdisciplinary Learning Objectives: Disease Prevention and Control
8.a. (Law & Policy. Connects with History & Social Science: Geography and Civics &
Government) Analyze the influence of factors (such as social and economic) on the treatment and management of illness.

Benchmarks for Science Literacy, AAAS

The immune system functions to protect against microscopic organisms and foreign substances that enter from outside the body and against some cancer cells that arise within. 6C/H1*

Some allergic reactions are caused by the body’s immune responses to usually harmless environmental substances. Sometimes the immune system may attack some of the body’s own cells. 6E/H1

Some viral diseases, such as AIDS, destroy critical cells of the immune system, leaving the body unable to deal with multiple infection agents and cancerous cells. 6E/H4

Vaccines induce the body to build immunity to a disease without actually causing the disease itself. 6E/M7** (BSL)

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