'Will the Vaccine Alter My Genes?' -- and Other Patient FAQs

Jan E. Patterson, MD, MS; Rukevwe I. Ehwarieme, MD


January 21, 2021

The bleak winter surge of COVID-19 across the country has been punctuated by hope in the form of effective and safe vaccines. States are receiving shipments of the Pfizer/BioNTech and Moderna mRNA vaccines, and as of this writing, about 15 million doses have been distributed and almost 5 million first doses received. Although vaccine enthusiasm is evident in some areas, especially with the current shortages of vaccine, there remain pockets of vaccine hesitancy that need to be addressed.

About one quarter of the public continues to be hesitant, though it varies by demographics. The highest rate of hesitancy is among Republicans (42%), persons aged 30-49 years old (36%), and rural residents (35%). And despite bearing more adversity in the pandemic, 35%-40% of Black adults would decline the vaccine or are reluctant, as are approximately a third of essential workers and even a third of those who work in healthcare delivery.

Fortunately, 85% of people trust their own doctor or healthcare provider to give them the best information. Thus, it is especially important for us to be prepared to answer our patients' questions. The most common reason for reluctance is concern about side effects. Other common reasons are concern that it is too new and the role of politics in vaccine development. Emergency authorization was associated with lower acceptance, but vaccine efficacy and safety were important factors for higher acceptance.

Here are some questions that patients may ask about the vaccine, as well as issues that are important to address in guiding them to vaccine acceptance.

Is the vaccine safe? What side effects can I expect?

Yes, the vaccine is safe. Short-term side effects are common and may include soreness in the arm, fatigue, headache, and muscle aches, and pain within 2-3 days of getting the vaccine. These are more common after the second dose and in younger people (Table).

Table. Pfizer/BioNTech COVID-19 Vaccine Adverse Effects


Younger group

(16 – 55 years of age)

Older group

(> 55 years of age)

Dose 1

Dose 2

Dose 1

Dose 2











Muscle Pain










Joint Pain











Reported less frequently in the older group and was similar after either dose


Reported less frequently in the older group and was similar after each dose

Some rare allergic reactions (increased heart rate, lowered blood pressure, swollen lips, hives) have occurred in people with a history of allergic reactions. The reactions were detected during the monitoring period after administration and treated successfully. Sites that give the vaccine should be equipped to treat this type of rare reaction. If a severe allergic reaction occurs after the first shot, a second shot is not recommended.

If you have a known allergy to a component of the vaccine, you should not take the vaccine. For instance, polyethylene glycol (PEG) is in the vaccine. This is a compound found in some foods, beverages, toothpastes, shampoos, and medications, and some people have a known allergy to it.

Participants rarely developed Bell's palsy, a temporary facial nerve paralysis. The rate at which this occurred, however, was not higher than expected in the general population, so it is not clear that this is due to the vaccine.

What should I do if I experience side effects?

Most side effects are short-lived and relieved with acetaminophen or ibuprofen. If a patient experiences a severe side effect after getting vaccinated, they and/or their vaccine provider should send a report to the national Vaccine Adverse Event Reporting System (VAERS), which tracks and monitors adverse effects.

Are there any long-term effects from the vaccine?

Monitoring of long-term safety data is still ongoing. Typically, vaccines only have short-term side effects. We do know that COVID-19 can have long-term effects — fatigue, shortness of breath, prolonged cough, joint pain, difficulty with concentration, depression, and more — so the disease is worth preventing by receiving the vaccine.

Is the vaccine effective?

Both of the recently authorized COVID-19 vaccines are effective. The Pfizer/BioNTech vaccine trial had 43,000 participants and 95% efficacy, and the Moderna vaccine trial had 30,000 participants and 94.1% efficacy. Vaccine effectiveness was comparable across subgroups by age, gender, race, ethnicity, and underlying conditions. Severe cases requiring hospitalization were avoided in vaccine recipients of both trials.

Effectiveness in the 95% range for a vaccine is exceptional. We don't have many vaccines with this kind of efficacy, so it is worth getting the shot.

How were these vaccines made so quickly? I don't trust them.

The SARS-CoV-2 genome was sequenced by early January 2020. This allowed characterization of the spike protein, the immunogenic protein on the coronavirus that allows for cell entry. Because of novel mRNA technology, the coronavirus did not have to be grown in eggs or cell culture to develop the vaccine. Also, the partnership with the federal government has allowed companies to develop the vaccine faster than they normally would. The committee that reviews the efficacy and safety data for the FDA (the Vaccines and Related Biological Products Advisory Committee) is served by respected experts from around the country, and they recommended authorization of these vaccines.

Will this new technology alter my genes?

This mRNA technology has been studied for decades. The mRNA sends a genetic message to cells to make spike protein, the protein that coronavirus uses to enter cells. The mRNA is very unstable and has to be encapsulated in lipids to make it to the cell and deliver the message. Once it is in the cell, the mRNA is rapidly destroyed by enzymes, so it does not stay around. When the cell makes spike protein, the body produces antibody to it.

The mRNA technology is safe, but vaccines with other technologies are being developed. Two vaccines that are currently undergoing phase 3 trials use virus that cannot replicate as a vector to carry the message to the cells. These are the Oxford/AstraZeneca and the Johnson & Johnson vaccines. The Novavax vaccine uses another technology that has previously been used in vaccines — a recombinant spike protein along with an adjuvant to stimulate the immune system.

What about the new variants I have heard about?

Viruses typically have mutations over time, and this virus is not an exception. There have been two significant variants documented recently — one in the United Kingdom and the other in South Africa. Though each of these has a number of mutations, the vaccine was designed to neutralize the entire spike protein, so the vaccine will probably still be effective. Studies are being done to specifically evaluate the efficacy of the vaccines against these variants.

Can I get compensation for a severe adverse reaction?

Vaccine companies are not liable if something unintentionally goes wrong with their vaccine. For a severe adverse effect, there is a process to apply for compensation through the National Vaccine Injury Compensation Program. It requires filing a petition with the US Court of Federal Claims and a review by the US Department of Health and Human Services medical staff, who will determine whether the claim meets criteria for compensation. [Editor's note: After the submission of this commentary, the authors have noted that under the Department of Health and Human Services public health emergency declaration, claims for COVID-19 vaccine injuries are brought under the Countermeasures Injury Compensation Program rather than the Vaccine Injury Compensation Program. The authors of The New England Journal of Medicine article point out that this program is more limited in compensation and qualifications, and call for Congress to rectify.]

In summary, the outstanding efficacy of the vaccines and their acceptance by millions of persons, including healthcare workers and leaders, have helped to decrease vaccine hesitancy, but reluctance remains in some groups. National and regional public health agencies and community leaders must continue to inform and educate the public, but the role of the healthcare provider in talking to individual patients will be a powerful and critical influence in increasing acceptance.

Jan E. Patterson, MD, MS, is a professor of medicine/infectious diseases and associate dean of quality & lifelong learning at the Joe R. and Teresa Lozano Long School of Medicine, UT Health San Antonio. She has had many publications and presentations on infectious diseases and healthcare epidemiology over a period of three decades. Her areas of expertise include clinical infectious diseases, infection prevention, antimicrobial resistance and stewardship, and integrative medicine. She has served in leadership positions regionally and nationally, including the boards of national professional organizations.

Rukevwe I. Ehwarieme, MD, is an infectious diseases fellow at the University of Texas Health San Antonio Long School of Medicine, where he is also a member of the COVID-19 Vaccine Task Force.

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