Answer Common Questions

• Yes. Hundreds of millions of people around the world have received COVID-19 vaccines and the results of ongoing safety monitoring are reassuring.
• Vaccines work by teaching the body to recognize and fight off the virus that causes COVID-19. After vaccination, people may notice their body gearing up to make antibodies and build immunity. Sometimes this means people feel feverish, nauseous, achy, or tired, and they may have a headache or a sore arm in the first few days after vaccination. These symptoms typically resolve on their own within a day or two.
• Any vaccination can result in a severe allergic reaction (called anaphylaxis), but these events are very rare (roughly 1 case per 200,000 to 1 million vaccinations), and every vaccination site has epinephrine (Adrenalin®) on hand to treat such rare reactions.
• A rare bleeding condition was identified within a couple weeks after several people received the Johnson & Johnson/Janssen COVID-19 vaccine. That condition is called thrombosis-with-thrombocytopenia syndrome (TTS), which is bleeding with low platelet counts. Discuss this situation with your vaccine provider.

Learn More

• Know the research on the safety of the COVID-19 vaccines.
• Review CDC’s Communicating About COVID-19 Vaccine Safety and Risk for more strategies you can use to emphasize the safety of these vaccines.

Information for Patients

CDC’s Safety of COVID-19 Vaccines

• No. None of the vaccines contain the live COVID-19 virus that causes COVID-19.
• It takes a few weeks for the body’s immune system to build a defense that protects against COVID-19, so it is possible some people might become infected with COVID-19 during this period.
• No vaccine is perfectly protective. It is possible for a small percentage of vaccinated people to be infected with COVID-19 despite vaccination. These people typically develop only a mild case of COVID-19.
• Patients may experience common postvaccination symptoms that feel like a COVID-19 infection, such as fever, fatigue, chills, and nausea.

• It is true that more experience keeps showing us new information, and we learn new things as time goes by because our safety monitoring systems are working.
• People can expect some side effects from the vaccine like headache, muscle ache, tiredness, or a slight fever. Such side effects reflect that the body is building an immune response that will protect against COVID-19. It is also important to remind patients that even if they don’t experience these symptoms, the vaccine is still working.
• There are reports of rare but more serious adverse events after vaccination. Most COVID-19 vaccine recipients do not develop these symptoms.
• Patients may not be aware that they can track their symptoms using v-safe, which is an app that will let them know symptoms they experience are reason to follow up with a doctor.

Patient Information

CDC’s summary of Selected Adverse Events Reported after COVID-19 Vaccination helps patients understand what we know about emerging, rare, adverse events after vaccination.

• Delayed side effects from vaccines are extremely rare. Considering the dozens of vaccines developed over the last 100 years, vaccine-related side effects are almost always detected within 6 weeks after vaccination.
• None of the COVID-19 vaccines were authorized until clinical trial volunteers were monitored for at least 2 months. Those volunteers have now been followed for 6 months or more. In addition, an extensive network of safety monitoring is in place to rapidly detect any potential safety issues.
• Once the vaccine teaches your body to recognize and fight off the COVID-19 virus, the vaccine is cleared from your body, which is what makes long-term side effects from vaccines so rare.

Learn More

Watch APhA’s Open Forum Webinar on The Long-term Effects of COVID-19 Disease: Impact on Patient Care to learn about the long-term effects of COVID-19 disease and the advantages of COVID-19 vaccination.

• According to CDC guidance, the Pfizer-BioNTech or Moderna COVID-19 vaccines are preferred over the Janssen COVID-19 vaccine for primary and booster vaccination in most situations. CDC recommendations allow for mixing and matching COVID-19 vaccine booster doses, meaning a booster dose of any FDA authorized or approved COVID-19 vaccine can be given regardless of the primary series administered. All available COVID-19 vaccines are very effective against severe disease, hospitalization, and death related to COVID-19.
• A small NIH study tested booster dose variations in people who had received a full vaccine series with one of the three FDA authorized or approved COVID-19 vaccines. The study concluded that any COVID-19 vaccine that is FDA approved or authorized as a booster dose will generate an immune response regardless of the primary vaccine series. More clinical trials are needed in this area. CDC is evaluating ongoing studies in this area and has not released information regarding any one booster vaccine being preferred or superior over another.
  • Study results showed that compared to receiving the same vaccine for the booster dose, receiving a different vaccine for the booster dose resulted in comparable or higher immune response.
  • These are interim findings from limited information. The study is not large enough to make comparisons between different COVID-19 booster regimens. Also, the FDA-authorized Moderna booster dose is half the dosage of what this NIH study tested.
• According to CDC guidance, people may consider the benefits and risks of each product and discuss with their healthcare provider which product is most appropriate for them.
  • Potential risks of a Janssen (Johnson & Johnson) COVID-19 booster include the rare risks of Guillain-Barré Syndrome (GBS) and thrombosis with thrombocytopenia syndrome (TTS). Based on data after receipt of a Janssen (Johnson & Johnson) COVID-19 primary dose, the group at the highest risk for GBS is men aged 50–64 years and the group highest at risk for TTS is women aged 18–49 years. Women aged 18–49 years should be made aware of the increased risk for TTS and the availability of mRNA COVID-19 vaccines for use as a booster dose.
  • Cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the outer lining of the heart) have been reported after Pfizer-BioNTech COVID-19 vaccination of children ages 12–17 years. These reactions are rare; in one study, the risk of myocarditis after the second dose of Pfizer-BioNTech in the week following vaccination was around 54 cases per million doses administered to males ages 12–17 years.
    • In general, adolescents ages 12–17 years have a higher risk for myocarditis than children ages 5–11 years. During clinical trials, no cases of myocarditis occurred in children ages 5–11 years who received the COVID-19 vaccine.