How Does COVID-19 Vaccines Work?

10, Aug 2021

Many people do not fully understand how the COVID-19 vaccines work.

Here is a breakdown to help people better understand how and why they work.

Pfizer and Moderna vaccines use novel messenger RNA (mRNA) technology. The Johnson & Johnson vaccine uses the more traditional virus-based technology.

Once the vaccine is administered, cells take up the mRNA and use it to produce the spike protein encoded within. These proteins then trigger a robust immune response (antibodies to the spike protein).
Dr. Sue Mitra

So, in case you encounter COVID, your antibodies will protect you.

The FDA-authorized COVID-19 vaccines are highly effective in protecting against severe illness by reducing the need for hospitalization, thereby reducing morbidity and mortality from COVID-19.

Just like with any other vaccine, the COVID-19 vaccine does have side effects that include, but are not limited to, arm redness and soreness at the site of the injection, fever, fatigue, and/or focal lymphadenopathy.

People with previous allergic reactions to another vaccine should be excluded from receiving the vaccine.

After receiving it, there have been some isolated reports of anaphylactic-like reactions; however, this is an infrequent occurrence.

The COVID-19 vaccine should be safe for those with weakened immune systems.

The protective response may not be as robust due to the immunodeficiency; however, there is no risk of contracting COVID-19 from this vaccine.

Expected immunity after receiving the vaccine is about 7-10 days after the second dose. You will receive partial immunity after the first dose.

For Moderna and Pfizer vaccines, do not count on one dose to fully protect you. You still have to get the second dose of the same vaccine for full protection.

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There remain a lot of challenges in reaching herd immunity through community infection and vaccination.

It is certainly not clear as to the duration of protection after complete recovery from COVID-19 illness.

Refusal to getting a COVID-19 vaccine due to possible side effects and/or their doubtful benefits are a few of the challenges. The disease will continue to spread if herd immunity is not achieved.

On the contrary, it is unclear how long the COVID-19 vaccines will protect the population from COVID-19.

With the new variants emerging, COVID-19 vaccines may have variable efficacy against some of the variants of the COVID-19 virus.

So, after receiving the vaccine, you should continue to wear a mask and social distance as the pandemic continues.

There is still a small percentage that will get and potentially transmit the virus despite vaccination.

August is National Immunization Awareness Month, which highlights the importance of recommended routine vaccines in your life.

Keeping up with necessary appointments and receiving routine vaccinations have been very difficult during the COVID-19 pandemic.

During this month, I encourage you to talk to your doctor to ensure that you and your precious family are protected against serious illnesses by getting caught up on your routine vaccinations.

Remember to get your COVID-19 vaccine at your earliest convenience as well.

Dr. Sue Mitra is Board Certified in Internal Medicine and accepting new patients. Please feel free to visit her website at She can be reached at 321-622-6222 to discuss more about the importance of vaccinations.


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