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Your Vaccination Guide

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Dr. Tista Ghosh

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Does the vaccine protect me from new variants?

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Expert Answers to Your Vaccine Questions

Check out these up-to-date insights and answers to your COVID-19 vaccine questions from our Chief Medical Officer and senior medical experts.

Are the vaccines safe? How many people were studied? Was that enough?

The Food and Drug Administration (FDA) sets tough standards that must be met before they will allow for an emergency use authorization (EUA) for a vaccine, which it granted to the Pfizer and Moderna vaccine in December 2020 and the Johnson & Johnson vaccine in February 2021. For safety, the data must include a period of at least two months after a person gets the second shot of the vaccine to watch for any late side effects. 


The Centers for Disease Control and Prevention (CDC) also reviews vaccine studies along with a group of doctors and other vaccine experts who don’t work for the government. These groups found that the vaccines are safe. Safety information will continue to be gathered as more and more vaccinations are given.


Pfizer, Moderna and Johnson & Johnson all tested their vaccines on large groups of people. The Pfizer SARS-CoV-2 vaccine studies had 43,448 people, and the Moderna SARS-CoV-2 vaccine study had more than 30,000 people. The Johnson & Johnson vaccine clinical trials enrolled 45,000 people.

What have been the main side effects experienced from the vaccines?

In most cases, post-vaccine symptoms are reported to include:

  • Pain at injection site
  • Fatigue
  • Headache
  • Muscle pain
  • Chills
  • Joint pain
  • Fever
  • Injection site swelling
  • Injection site redness

For Johnson & Johnson vaccines, rare blood clots and low platelets developing 1-2 weeks after vaccination have been reported. In response to these reports, the FDA and CDC decided to pause the use of the Johnson & Johnson vaccine beginning April 12 2021. 

  • If you have received the Johnson & Johnson vaccine, you are advised to monitor for severe headache, abdominal pain, leg pain, or shortness of breath occurring within three weeks after vaccination, and should contact your local health care provider for evaluation right away if such symptoms occur.
  • If you received the Johnson & Johnson vaccine and have not developed any of the side effects associated with signs of blood clots, as noted above, within three weeks after vaccination, the risk of an adverse reaction is unlikely.

Read this release for more information: https://www.cdc.gov/media/releases/2021/s0413-JJ-vaccine.html


How can we best distinguish expected vaccine side effects from symptoms of the illness?

If patients have symptoms of injection site pain/tenderness, fatigue, fever, muscle/body aches, etc. within hours to a couple days after receiving the injection, then these are very likely related to the vaccine and not COVID-19. If there are other more specific symptoms like a runny nose, coughing, chest pain, loss of taste/smell, vomiting or diarrhea then it could be COVID-19, or some other virus, and not likely caused by the vaccine. If this occurs, you should isolate yourself per CDC guidelines and get tested for COVID-19.

Will the vaccine protect me from the new variants?

At this time, the current vaccines will still protect most people from the new coronavirus variants, including the UK variant that is now spreading in the US. There are two other variants, one found initially in South Africa and now in several other countries, and another in Brazil that researchers are closely studying that may infect people who already had COVID-19 in the past. Studies are underway to find out if the current vaccines can protect against these variants. There are some new variants in the US as well that researchers are still learning about and watching. These new variants are another reason why it’s important to continue to wear masks, social distance and practice hand hygiene to prevent the spread of COVID-19. For updated news about new variants, the CDC website is a good resource.

Should I worry about how fast these vaccines were created?

No. There are many reasons that safe vaccines could be made so quickly. First, the technology used to make the mRNA vaccines has been studied and created for more than a decade. Second, making a vaccine with the mRNA technology (the Pfizer and Moderna products) is also much simpler and faster than the other forms, such as those used to make the flu vaccine. So there is a shorter manufacturing time. The Johnson & Johnson vaccine uses a process already in use for other non-COVID-19 vaccines. Third, the US government helped fund the studies and vaccine creation, so that helped speed up the process as well. Lastly, the pandemic made the need for the vaccine a top priority. So getting enough people to take part in the studies was quick and easy.

These studies were shorter than normal because of the urgent need for the vaccine during the pandemic. Are there any long-term effects that we need to be watching out for in the upcoming year?

There are no long-term effects to watch out for. But scientists will continue to watch for side effects that people report after getting the vaccine through an app on their smartphones or computers, and information they share with their vaccine providers.

My parents are elderly and are not sure they should get the vaccine. Does it work in older adults? Did they study it in older adults?

Yes, Pfizer, Moderna and Johnson & Johnson did study their vaccines in older people, a group who often don’t respond as strongly to vaccines. The success rate of vaccines is still very good at 94% for the Pfizer vaccine in people 55 and over and 86% for the Moderna vaccine in people 65 and older. For comparison, younger people had a 95% success rate for these vaccines. So, these two vaccines are still very useful for preventing COVID-19 in older people.

Should I be concerned about the use of new technology (mRNA) to make the Pfizer and Moderna vaccines?

No, you should not be concerned about the technology used to make the vaccines. Like all vaccines, COVID-19 vaccines have been tested for safety before being allowed to be used in the United States. It’s also important to know that the mRNA technology used for the Pfizer and Moderna vaccines was not just created for the novel coronavirus. It has actually been studied and designed for more than a decade. So, researchers and vaccine experts already had experience with it.

The three available vaccines do not contain a live virus so they do not carry a risk of causing COVID-19 in anyone. Also, material from the mRNA vaccine never enters the center of the cell and does not affect the person’s own DNA. Lastly, after our body uses the information in the mRNA it is broken down by our cells. Then the immune system makes protective antibodies to protect us against the virus.

The Johnson & Johnson vaccine is the newest vaccine to be approved in the US. How does it work? Why was it paused?

The Johnson & Johnson vaccine differs from the currently available COVID-19 vaccines from Pfizer and Moderna in a few ways. First, it is given in a single dose. Additionally, this vaccine uses a common cold virus, to introduce the spike proteins of COVID-19 into our cells, thereby evoking an immune response. It is important to understand that this is an altered form of the common cold virus that cannot cause any harm or multiply, so no one will get sick from it. This common cold virus has been used in this same way for other vaccines, as well, with no problems. Another difference between this vaccine and the two currently available in the US is that it does not require such cold temperatures to transport and store unlike the current MRNA vaccines. This should make it less complicated for hospitals, clinics, and pharmacies to handle. 


The results from Johnson & Johnson large clinical trials indicate that the vaccine has an efficacy of 72% in the United States arm of the trial, and 85% when they looked at specifically its ability to prevent serious illness overall. The Johnson & Johnsonvaccine will work well to prevent COVID-19, and especially well to prevent serious illness from developing.


Regarding the safety of the Johnson & Johnson vaccine, an independent group of experts not involved in the clinical trials, the Data and Safety Monitoring Board (DSMB), reviewed Johnson & Johnson data and did not report any significant safety concerns relating to the vaccine. Their review of adverse events indicated that a single-dose of Johnson & Johnson COVID-19 vaccine candidate was generally well-tolerated. Importantly, no instances of anaphylaxis (a life threatening allergic reaction) were reported. 


On April 13, 2021 it was reported that rare blood clots and low platelets were developing 1-2 weeks after vaccination. In response to these reports, the FDA and CDC decided to pause the use of the Johnson & Johnson vaccine beginning April 12 2021. 

  • If you have received the Johnson & Johnson vaccine, you are advised to monitor for severe headache, abdominal pain, leg pain, or shortness of breath occurring within three weeks after vaccination, and should contact your local health care provider for evaluation right away if such symptoms occur. 
  • If you received the Johnson & Johnson vaccine and have not developed any of the side effects associated with signs of blood clots, as noted above, within three weeks after vaccination, the risk of an adverse reaction is unlikely.

Read this release for more information: https://www.cdc.gov/media/releases/2021/s0413-JJ-vaccine.html


Did they study the vaccine in people of color?

  • For the mRNA vaccine from Pfizer, 10% of U.S. people in the study were Black, 13% were Hispanic, 6% were Asian, and less than 2% were Native American. Over all the studies Pfizer did worldwide, not just in the US, 10% of the people were Black, 26% were Hispanic, 5% were Asian, and less than 1% were Native American. 
  • In the Moderna vaccine studies, roughly 20% of the people were Hispanic, 10% were Black, and 4% were Asian. Information on the number of American Indians in the study was not provided.
  • Among U.S. participants in Johnson & Johnson’s phase 3 trial, 74% were white, 15% were Hispanic, 13% were Black, 6% were Asian, and 1% were Native American.

Should people with certain autoimmune diseases or other conditions avoid the vaccines?

No, having an autoimmune condition is not a reason to avoid the vaccine. The vaccine is approved for people with autoimmune diseases and weakened immune systems from health conditions or a medication. To understand the risks and benefits, people with these conditions should consult with their care provider before getting the vaccine.

I’m pregnant, breastfeeding, or trying to get pregnant. I know they didn’t study the vaccines in pregnant women so should I get it?

It is true that pregnant and breastfeeding women were not included in the studies. But the way the vaccines work makes it unlikely that it could have a harmful effect on pregnancy or a breastfed baby. In fact, the Center for Disease Control (CDC) and the American College of Obstetricians and Gynecologists (ACOG) both state that pregnancy and breastfeeding are not reasons to avoid the vaccine. If a pregnant or breastfeeding person is part of a group that is recommended to receive a COVID-19 vaccine (e.g., healthcare personnel), they may be offered the vaccine. But to understand the risks and benefits, they should consult with their care provider before getting it.

They didn’t study the vaccine in kids. Does that mean they can’t get the vaccine? Would it be unsafe?

Yes, none of the vaccines are approved for use in children. The Pfizer vaccine is not approved for use in children under the age of 16, and the Moderna and Johnson & Johnson vaccines are not approved for children under 18. We do not have any safety information on how the vaccine works in children as they were not included in the study. We will learn more about this information after further studies are done that include children.

I got sick, sore, or swollen after the first shot. Should I really get another one?

Yes, to be fully protected you need to get both shots of the vaccine. The vaccine does not take full effect and cannot protect you from COVID-19 until about one to two weeks after the second shot.

How effective are the vaccines in preventing severe COVID-19 disease?

All three vaccines (Pfizer, Moderna, and Johnson & Johnson) have demonstrated to be 100% effective at preventing severe disease once the patient is fully vaccinated.

How effective are the vaccines in preventing people from spreading the virus when they have no symptoms?

While we do know that the currently available COVID-19 vaccines are very good at preventing someone from getting symptoms from the virus, we don’t yet know if they can prevent people from spreading the virus when they have no symptoms. So, we still need everyone to wear masks after getting the vaccine until this information is available. We will share when the CDC shares that it is safe to no longer practice masking precautions.

Will I still have to wear a mask if I get the vaccine?

The CDC recommends that until the majority of Americans have been vaccinated, we must all continue to wear masks and social distance when in public spaces, and avoid medium to large gatherings. However, for those that are fully vaccinated some of the restrictions have been eased in the following ways: 

  • If you are fully vaccinated you may visit with other fully vaccinated people indoors without wearing masks or physical distancing
  • You may visit unvaccinated people from one household, as long as these people are generally healthy and at low risk for severe COVID-19 disease, indoors and without wearing masks or physical distancing
  • You do not need to quarantine or get tested for COVID-19 following a known exposure, if you remain asymptomatic

For now, fully vaccinated people should continue to:

  • Take precautions in public (mask and physical distancing)
  • Wear masks/ physical distance when visiting with unvaccinated people at increased risk for severe COVID-19 or visiting those who have someone in their household at risk
  • Mask, physical distance when visiting with unvaccinated people from multiple households
  • Avoid medium/large gatherings
  • Get tested if experiencing COVID-19 symptoms
  • Follow guidance issued by individual employers
  • Follow CDC and health department travel requirements

How effective is each shot of the Pfizer and Moderna vaccines? How long do I need to wait between each shot?

The efficacy after the first dose of the Pfizer COVID-19 vaccine is about 52% effective. After two doses of the Pfizer vaccine it reaches 95%. The Moderna vaccine study did not have a formal study where they measured the power of the single dose. So we don’t know exactly how effective a single dose is, but after the second dose the Moderna vaccine was 94.5% effective. The Johnson & Johnson vaccine is only one dose, and has an efficacy of 66% overall, and 72% in the US arm of their trials. 

For the Pfizer vaccine, you need to wait 21 days between doses. For the Moderna vaccine, it is 28 days between doses. As noted, the Johnson and Johnson vaccine is only one dose.


The reported full efficacy of >90% for the vaccines comes at 7 days after the second dose for Pfizer, and for the Moderna vaccine it is at 14 days after the second dose. The reported efficacy of the Johnson & Johnson vaccine is 66% overall at 14 days after the single injection, 72% if you look just at the United States arm of their trial. 

How long does the vaccine last in the body?

  • So far, we have evidence from studies that the protection from the mRNA vaccine from Pfizer lasts at least 6 months. As more time goes by and the studies continue, we will know if and when a booster vaccine might be needed.
  • We don’t yet have a report from Moderna regarding how long their mRNA vaccine will protect us, however we are confident it will be similar to the Pfizer vaccine. 
  • The Johnson and Johnson vaccine has not been in use long enough for us to have reliable data on this yet.

Which vaccine is better? Which vaccine should I get?

Both the Pfizer and Moderna mRNA vaccines had a success rate of well over 90% in preventing illness from COVID-19. So, both are equally effective at preventing the illness from COVID-19. The Johnson & Johnson vaccine has a somewhat less vigorous ability to prevent the symptoms of COVID-19, 66% overall, and 72% in the US, but this is still very acceptable for a vaccine. Importantly, the Johnson & Johnson vaccine performs very well in preventing serious illness from COVID-19 with an efficacy of 85%, meaning that those who did get ill from SARS-CoV-2 infection after vaccination had a much less severe illness. And it is really successful in preventing (100%) hospitalizations due to COVID-19. Also, it has the added benefit of being only one dose. 


*For Johnson & Johnson vaccines, rare blood clots and low platelets developing 1-2 weeks after vaccination have been reported. In response to these reports, the FDA and CDC decided to pause the use of the Johnson & Johnson vaccine beginning April 12 2021

I’m partially vaccinated (received one of two doses of either Moderna or Pfizer). How protected am I after one dose?

Evidence indicates that after the first dose of the mRNA vaccine, the efficacy is about 80%, which is very good. That said, after the second dose the efficacy is over 90%, so you are still highly encouraged to get the second dose for full protection.

Herd Immunity Questions

What percent of the population will need to get vaccinated to get “back to normal”?

Public health officials estimate that 70 - 75 % of people need to be vaccinated before we can get back to “normal life” and move freely through society without masks and social distancing.

Should I get the vaccine if I already had COVID-19?

Yes, even if you had COVID-19, you should still get the vaccine because it is not clear how long the immunity lasts after having had COVID-19. If you have had COVID-19 within the last month, please contact your local health provider or our health team to determine when you should get the vaccine.

Should I get an antibody test before getting the vaccine?

Antibody testing is not currently recommended to assess the need for vaccination.

Logistical Questions

Why are these other people being prioritized before me?

There are not enough vaccines for everyone to get it right away. While more vaccine doses are being made, people most at risk of getting COVID-19 will get it first. This includes healthcare staff and patients in long-term care facilities. Each state has created their own prioritization decisions based on CDC recommendations and state demographics.

How do I prepare for my vaccine appointment?

In preparation for your vaccine appointment, be sure to take your driver's license / ID card, and your insurance card with you along with the vaccination form filled out. Be sure to wear a short-sleeve shirt, or a shirt with sleeves loose enough to easily pull it up and allow access to your upper arm. It is not recommended that you take any Tylenol or Ibuprofen prior to the vaccine, but these can be taken afterwards if needed for minor aches and pains that might occur.

Is it safe to travel if I've been vaccinated?

While the CDC still recommends against travel in general, they have updated their travel guidelines specifically for fully vaccinated travelers: 

  • Fully vaccinated people can resume domestic travel and do not need to get tested before or after travel or self-quarantine after travel
  • Fully vaccinated people do not need to get tested before leaving the United States (unless required by the destination) or self-quarantine after arriving back in the United States.
  • Travelers still need to show a negative test result or documentation of recovery from COVID-19 before boarding a flight to the United States.
  • Travelers should still get tested 3-5 days after international travel.
  • Travelers do NOT need to self-quarantine after arriving in the United States.

How much does the vaccine cost?

COVID-19 vaccine is free. The health care provider may choose to charge an administration fee for distributing the vaccine, if this occurs the fee will be covered by your insurance company. For uninsured patients, the government will cover the administration fee. No one can be denied a vaccine if they are unable to pay the vaccine administration fee.

DISCLAIMER: The advice in this article is intended for informational purposes only. It is not meant to replace or substitute for advice, diagnosis or treatment from a medical professional. Please consult your doctor with questions you may have regarding a personal medical condition or treatment.

Meet Our Doctors

Dr. Tista Ghosh

Dr. Ghosh is the Senior Medical Director for Grand Rounds and our leading expert in epidemiology, the study of understanding and controlling disease. She was trained at America’s health protection agency, the Center for Disease Control and Prevention, and has served as the Chief Medical Officer for the state of Colorado and on the U.S. Community Preventive Services Task Force. She works to educate Grand Rounds members about COVID-19 vaccines and prevention and other diseases to make a positive impact on public health.

Dr. Tista Ghosh, MD, MPH

Dr. Melody Msiska

Dr. Msiska is a Staff Physician and Telemedicine Service Lead at Grand Rounds. She oversees our team of top doctors, nurses and healthcare experts as they meet and care for patients from across the country in virtual visits. Whether by phone, app or computer, Dr. Msiska is passionate about using technology to make sure everyone has access to high-quality healthcare so they can get better faster and save time and money along the way.

Dr. Melody Burns Msiska, MD

Dr. Todd Thames

Dr. Thames is a Senior Medical Director at Grand Rounds. He believes strongly in listening closely to patients to understand the many issues and experiences that affect their health. After decades of working in hospitals and the healthcare industry, Dr. Thames focuses his strengths in healthcare management, medical education and patient care on raising the standard of healthcare for Grand Rounds members.

Dr. Todd Thames, MD, MHA, FAAFP

Dr. Heather Hockenberry

Dr. Hockenbery is our Senior Staff Physician and Clinical Lead at Grand Rounds. She brings over a decade of direct patient care experience to her role as leader and mentor to our large medical team. Drawing on her vast knowledge of medicine and her one-on-one experience caring for patients from all walks of life, Dr. Hockenberry helps her team deliver the highest possible healthcare to all our Grand Rounds members.

Dr. Heather Hockenberry, MD

Andrea Ballesteros, RN

Andrea Ballesteros comes to the Grand Rounds team after years of experience caring for patients in a hospital setting. As a Spanish-Speaking Bilingual Registered Nurse, she makes sure Grand Rounds members get the care and information they need in the language they understand. From connecting members to the right doctors for their conditions to supporting them through COVID-19 issues and behavioral health crisis, Andrea brings high-quality compassionate care to every member’s experience.

Andrea Ballesteros, RN

Trusted Sources

Where to turn for additional vaccine resources

CDC COVID-19 vaccination information

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