COVID-19 Vaccine FAQs with Benjamin Estrada, M.D.

Posted on January 28, 2021 by Carol McPhail
Carol McPhail

A USA Health resident receives the COVID-19 vaccine. data-lightbox='featured'

Benjamin Estrada, M.D.

How much do you know about the Pfizer-BioNTech and Moderna vaccines now being administered to protect against COVID-19?

We asked infectious disease specialist Benjamin Estrada, M.D., who also serves as assistant dean for educational strategies and faculty development, and professor and vice chair of pediatrics at the USA College of Medicine, to answer the most frequently asked questions about these vaccines.


Q: How safe are the COVID-19 vaccines?

A: Both of the currently available COVID-19 mRNA vaccines have been found to be safe. Despite a relatively high frequency of side effects, the frequency of serious adverse or life-threatening side effects is very low. Anaphylaxis has been reported in only a handful of patients after administration of thousands of doses. 

It is important to emphasize that mRNA in the doses does not alter a person’s DNA, and its main mission is to deliver a translation message to the cell’s ribosomes for the production of the spike protein. The mRNA undergoes rapid intracellular degradation afterward.


Q: Do I need to be vaccinated if I've already had a confirmed case of COVID-19?

A: Yes. People who already had COVID-19 were included in the studies for both vaccines. Both vaccines were found to be safe in the group of subjects with a previous history of COVID.


Q: What are the most common side effects of the vaccine?

A: Pain at the site of injection, headache, fatigue, low-grade fever and muscle aches and pains. 


Q: When can I be vaccinated if I've recently or currently have a confirmed case of COVID-19?

A: You can be vaccinated after completing the isolation procedures prescribed after the diagnosis of COVID-19.


Q:  Do I still need to wear a mask and practice social distancing after I've been vaccinated?

A: Yes. That is because although we know that the mRNA vaccines decrease significantly the risk of hospitalization and the risk of developing symptomatic diseases, we do not know yet whether they prevent asymptomatic infection and transmission. 


Q:  What is the level of protection after the first dose of the vaccine? 

A: The COVID-19 mRNA vaccines are about 50 percent effective about two weeks after the first dose. This is because it takes 12 to 14 days after the first dose to develop an initial immune response. 


Q: When is full immunity achieved after the second dose of the vaccine?

A: The vaccine shows 95 percent efficacy against symptomatic disease four to five weeks after the initial dose or one to two weeks after the second dose.


Q:  How long is the vaccine effective?

A: We don’t know yet. The studies performed so far have shown the concentration of neutralizing antibody production induced by the vaccine is equal to or higher than the concentration of neutralizing antibodies induced by natural infections. In addition, both vaccines and natural infection elicit a cytotoxic CD8 response. Recently published information suggests that an immune response can be detected as long as eight months after natural infection. 

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