Vaccine Safety


Is the vaccine safe?

The data from clinical trials indicate that the Pfizer-BioNTech, Moderna, and Janssen vaccines are safe. All vaccines have undergone extensive clinical trials that tested for safety and efficacy before being submitted to the FDA for Emergency Use Authorization. To learn more about each vaccine, please reference the vaccine fact sheets:

What are the common side effects?

Please reference the Moderna, Pfizer-BioNTech, and Janssen vaccine fact sheets for the most up-to-date information about side effects:

Does the COVID vaccine cause inflammation in the heart

Rare cases of inflammation of the heart muscle (myocarditis) and inflammation of the lining surrounding the heart (pericarditis) have been reported with the Pfizer-BioNTech and Moderna vaccines. These have typically occurred in males aged 12 to 29 years within a few days after receiving the second dose of vaccine. Most patients have required hospitalization with resolution of their acute symptoms. The benefits of the vaccine in preventing severe COVID-19 and hospitalizations outweigh the rare risk of myocarditis or pericarditis.

Does the COVID vaccine cause Guillain-Barré syndrome?

Rare cases of Guillain-Barré syndrome (GBS) have been reported in patients who received the Janssen/Johnson & Johnson vaccine. GBS is an neurologic disorder in which the immune system damages nerve cells, which can result in muscle weakness or paralysis. Most patients fully recover from GBS. To date, only 100 cases have been identified among 12.5 million vaccine recipients. The benefits of the vaccine in preventing severe COVID-19 and hospitalizations outweigh the rare risk of GBS.

Does the COVID vaccine cause blood clots?

On April 13, 2021, the FDA issued a pause on the Janssen vaccine to investigate reports of rare blood clotting disorders occurring after vaccination. The safety of the Janssen vaccine was affirmed and use resumed on April 23, 2021. Occurrences of blood clots were found to be extremely rare, with a slight increased risk in women older than 50 years of age (7.0 cases per million vaccinated). Blood clots have not been associated with the Pfizer-BioNTech or Moderna vaccine.

The cause of blood clots appears to be similar to a disorder called heparin-induced thrombocytopenia (HIT), an immune reaction to a blood thinner, heparin, commonly used in hospitalized patients. HIT decreases platelet levels and may cause blood clots. Patients who have a HIT within the past 30 days or other immune conditions that causes low platelets should receive either the Pfizer-BioNTech or Moderna vaccine instead. Patients with a history of blood clots or other conditions that may cause blood clotting that is not triggered by heparin or the immune system may receive any FDA-authorized COVID-19 vaccine, including the Janssen vaccine.

For more information, read the Center for Disease Control and Prevention's (CDC's) Interim Clinical Considerations for Use of COVID-10 Vaccines.

What if I have a reaction, side effect, or an adverse event?

If you experience a severe allergic reaction, call 911 or go to your nearest hospital.

If you believe you are having an adverse reaction, you should contact your health care provider and seek medical attention immediately. Adverse events following vaccination should be reported through the Vaccine Adverse Event Reporting System (VAERS) (1-800-822-7967 or through their website). Please note: Dartmouth-Hitchcock employees should follow guidance outlined in the employee frequently asked questions found on the employee intranet.

The CDC is implementing a new smartphone-based tool called v-safe to check-in with people about side effects after they receive a COVID-19 vaccine. When you receive your vaccine, you should also receive a v-safe information sheet telling you how to enroll in v-safe. If you enroll, you will receive regular text messages directing you to surveys where you can report any problems or adverse reactions you have after receiving a COVID-19 vaccine.

Is the vaccine a live vaccine?

No, the vaccine does not contain any live virus.

Can I receive the COVID-19 vaccine if I am pregnant or breastfeeding?

As pregnant women were not included in the vaccine clinical trials, there is not enough data to know if the vaccine is safe for pregnant or lactating women. We recommend that you reference the vaccine fact sheets and recommendations from the American College of Obstetricians and Gynecologists (ACOG) listed below. Pregnant and lactating women should also contact their health care provider to discuss the current information available and each women's individual circumstance before making a decision about receiving the vaccination.

Can I receive the COVID-19 vaccine if I have had a severe allergic reaction to another vaccine?

If you have had a severe allergic reaction after a previous dose of this vaccine, or if you have had a severe allergic reaction to any ingredient in the vaccine, the Emergency Use Authorization Fact Sheet states that you should not get the Pfizer-BioNTech, Moderna COVID-19, and Janssen vaccine. We recommend that individuals with a history of anaphylaxis (severe, potentially life-threatening allergic reaction) consult their health care provider on making the decision as to whether or not to be vaccinated.

Does the COVID-19 vaccine interfere with mammogram screenings?

Any recent vaccination including those that you may receive, or have received, in the past for the flu, Shingles and now for COVID-19, can cause the lymph nodes in the armpit on the injected side to become temporarily enlarged. This lymph node enlargement may show up as an abnormality on the mammogram. If that were to happen, we would then recommend additional imaging. Most of the time, however, there is no observable change noted on the mammogram. At your mammogram appointment, the technologist will ask you if you received a vaccine in the arm in the last 2 months.

Please do not delay your mammogram screening, but if you are able to schedule your screening before you get your COVID-19 vaccine or 8 weeks after getting the vaccination, we encourage you to do so.

As always, if you have a sign or symptom of breast cancer you should not delay seeking treatment under any circumstances.

Can I get my flu shot at the same time as my COVID-19 vaccine?

The CDC has said that COVID-19 vaccines and other vaccines can be administered at the same time. This includes receiving both the COVID-19 vaccine and other vaccines, like the flu shot, on the same day. However, if you have a history of reaction to the flu shot, talk to your provider first.

Should children be getting the COVID-19 vaccine?

The CDC's advisory committee has advised that the Pfizer-BioNTech COVID-19 vaccine is safe and effective for people age 12 and older. Pfizer announced in March that clinical trials performed in this age group found “100 percent efficacy and robust antibody responses.”

Despite the fact that many children experience less severe illness from COVID-19, some children suffer serious complications. There is also growing evidence that as many as 25% of children suffer from symptoms such as respiratory issues, fatigue, and stomach problems, for weeks or months (sometimes referred to as “long haul” disease). And, just like adults, children who have few or no symptoms can still transmit the virus to others.

The surest way to protect children and our communities from the harmful effects of COVID-19 is to get the vaccination.

Is it safe to get a COVID-19 vaccine if I have an underlying medical condition?

Yes. COVID-19 vaccination is especially important for people with underlying health conditions like immune system issues, heart disease, lung disease, diabetes, and obesity, as these increase the risks and severity if you were to get COVID-19.

Patients with a history of myocarditis (inflammation of the heart muscle) or pericarditis (inflammation of the lining surrounding the heart) may receive the COVID-19 vaccine after the episode has completely resolved (no symptoms and no evidence of ongoing heart inflammation).

Should I get a COVID-19 vaccine if I've had multisystem inflammatory syndrome in children (MIS-C) or adults (MIS-A)?

It is unknown whether patients with MIS-C or MIS-A are at risk of developing the syndrome again following reinfection or in response to vaccination. Patients with MIS-C or MIS-A may choose to be vaccinated after considering clinical recovery, personal risk for severe COVID-19, and the unknown safety data for using vaccines in this population. A conversation with your health care provider may assist in your decision, but it is not required. Patients may also opt to defer up to 90 days from the date of diagnosis with MIS-C or MIS-A.

For more information, please visit the CDC's Multisystem Inflammatory Syndrome (MIS-C) page.

I recently received a dermal filler. Is it safe to get the COVID-19 vaccine?

Infrequently, people who have received dermal fillers might experience swelling at or near the site of filler injection (usually face or lips) following administration of a dose of an mRNA COVID-19 vaccine. FDA-authorized COVID-19 vaccines can be administered to people who have received injectable dermal fillers who have no contraindications or precautions for vaccination; however, these people should contact their health care provider for evaluation if they experience swelling at or near a dermal filler site following vaccination.