How your body builds immunity against COVID-19


by David Winter, MD

Mar 9, 2021

After receiving the vaccine for COVID-19, folks are asking, what happens with our immune systems? What is actually going on inside of the body? And how long does it take to build immunity? Here is a breakdown of information on how vaccines work.

Step one: Build a defense 

Our immune systems have defense mechanisms that are designed to identify invading organisms, which they then destroy. The first encounter our body has with a new disease may catch our immune system off guard and take a while to rev up. Vaccines help by prepping our immune systems to be ready in advance, giving the immune system a head start on viruses and other invaders.

An easy way to picture this is to compare it to a nation’s army. If a country waited until it was challenged by another, the invaders have an advantage. It takes armies a while to gather a group of dedicated soldiers and then time to properly train them.

Step two: Respond rapidly 

Vaccines work in a similar way — they train our immune system to make specific antibodies which stay alert for infectious diseases that might invade us. This gives our immune systems the opportunity to respond rapidly and at a high activity level when exposed to the disease. 

The individual success of vaccines depends on the stability and consistency of the enemy virus. For example, a measles vaccine works for a lifetime. Influenza, on the other hand, mutates a lot and requires newly formulated vaccines every year.

Related: So you got the COVID-19 vaccine, now what?

Effectiveness of COVID-19 vaccines 

So, how effective are the coronavirus vaccines? Time will tell, but scientists predict that they will work better than influenza vaccines, meaning that they should last for at least a year and maybe longer. Learn more about the different COVID-19 vaccines here.

Another important concept to understand is that vaccines don’t just work on individuals; they protect entire populations. Once enough people are immunized, opportunities for an outbreak of disease become so low that even people who are not immunized benefit. This concept is called herd immunity.

For most diseases, at least 70 percent of the population must develop immunity to eradicate a disease. That includes those who have been vaccinated and those who develop immunity by surviving the infection. Given the choice, the better option is a vaccine shot. 

Remember that it takes time, possibly a week or two, for each individual body to build protection, and we don’t yet know whether you can transmit the virus after you’ve been vaccinated. Be sure to continue to take the safety measures needed to keep you and those around you safe, including wearing a mask, physical distancing from others and washing your hands.

Get the latest information on COVID-19 and tips to stay healthy here.

About the Author

David Winter, MD, is an internal medicine physician on the medical staff at Baylor Scott & White Signature Medicine – Tom Landry.

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