Vaccine Safety

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Expected side effects after COVID-19 vaccination

On the arm where you got the shot

  • Pain
  • Swelling

Throughout the rest of your body

  • Fever
  • Chills
  • Tiredness
  • Headache

COVID-19 vaccines commonly cause pain and swelling in the arm where you got the shot and can cause fever, chills, tiredness, and headache. These are short-term side effects that may occur in the week after you receive your shot.

Although these symptoms go away on their own, you can talk to your doctor about taking over-the-counter medicine like ibuprofen or acetaminophen after you receive your vaccine. Do not take extra medicines before the shot because it is not known if this could make the vaccine less effective at protecting you. It is okay to take your usual daily medications.

Some people have the same or worse side effects with the second shot, but these side effects also go away on their own. If you do not have side effects, it does not mean that the vaccine is not working. Some people have no side effects at all, and the vaccine is still effective.

To reduce the pain and discomfort
where you got the shot

  • Apply a clean, cool, wet washcloth over the area.
  • Use or exercise your arm.

To reduce the discomfort from fever

  • Drink plenty of fluids.
  • Dress lightly.

If you have pain or discomfort, talk to your doctor about taking an over-the-counter medicine, such as ibuprofen or acetaminophen.

The CDC’s website has more information about what to expect after vaccination and what to do if you experience additional side effects.

V-safe

V-safe is CDC’s smartphone-based, after-vaccination health checker for people who receive COVID-19 vaccines. V-safe uses text messaging and web surveys from CDC to check in with vaccine recipients following COVID-19 vaccination. V-safe provides second vaccine dose reminders if needed, and telephone follow up to anyone who reports medically significant adverse events.

Note: V-safe cannot schedule vaccine appointments, including second doses of COVID-19 vaccines. If you need to schedule, reschedule, or cancel a COVID-19 vaccination appointment, contact the location that set up your appointment or a vaccine provider in your area.

V-safe is CDC’s active monitoring system for COVID-19 vaccine safety. It is available for every vaccine recipient and encourages people to check in regularly. V-safe works alongside existing robust systems designed to monitor vaccine safety, including VAERS, which alerts the CDC of adverse events. Milder side effects are also helpful to learn about, so when you participate with v-safe you’re supporting vaccine safety with the additional information you provide to the CDC.

We encourage everyone to sign up online for v-safe at the time of vaccination:
V-safe: after vaccine health checker

Vaccine Adverse Event Reporting System (VAERS)

The Vaccine Adverse Event Reporting System, or VAERS, is one way the CDC monitors vaccine safety. Anyone may submit a report to VAERS about a medical event after vaccination, even if they aren’t sure if it is related to vaccination. Vaccine providers are required to report all severe or unexpected events after vaccination, regardless of whether they think the event could have been related.

All deaths occurring after vaccination must be reported, even if they were expected or due to other causes. The information in each report is not checked before it is posted for public viewing on the VAERS site, although identifying details are removed. CDC has a team of clinical specialists that investigate each safety event reported to VAERS; deaths are investigated within 24 hours.

Investigation of vaccine safety reports takes place on a federal level. This means that while CDC’s team investigates VAERS reports, in particular any reports of serious or unexpected events, the State of Alaska does not have access to this information and does not conduct a separate investigation. Vaccine safety events are not reportable to the State of Alaska and instead are reported to federal systems only. For questions about specific VAERS reports, please contact CDC.

The CDC follows cases of anaphylaxis reported to VAERS or another reporting system, including v-safe, VAERS, CISA, Vaccine Safety Datalink, ongoing clinical trial data in partnership with the FDA, and the National Healthcare Safety Network. There are several published reports regarding CDC findings around cases of anaphylaxis occurring after COVID-19 vaccines:

Of note, both of these studies highlighted that there was no geographic predominance among anaphylaxis cases, meaning that there is no reason to think that people in a certain state or area are at higher risk.

An overall assessment by the CDC vaccine safety team found that cases of anaphylaxis were rare.

The CDC and the FDA also look at events occurring in people over the course of their lives among both groups that have received a vaccine and groups that have not. Fortunately, no serious medical problems have been found to be more common in people who have had the vaccine. So far, the groups getting COVID-19 vaccines have had fewer overall medical events than similar groups of people who haven't had the vaccine, and this analysis does exclude medical problems caused by unvaccinated people getting COVID-19. If serious safety issues are found, these are made public and vaccination could be paused. No serious safety issues have been found with the COVID-19 vaccines.

Further resources

Strengths and Limitations of VAERS Data

When evaluating VAERS data, it is important to understand the strengths and limitations. VAERS data contain both coincidental events and those truly caused by vaccines.

Strengths

  • VAERS collects national data from all U.S. states and territories.
  • VAERS accepts reports from anyone.
  • The VAERS form collects information about the vaccine, the person vaccinated, and the adverse event.
  • Data are publicly available.
  • VAERS can be used as an early warning system to identify rare adverse events.
  • It is possible to follow-up with patients to obtain health records, when necessary.

Limitations

  • It is generally not possible to find out from VAERS data if a vaccine caused the adverse event.
  • Reports submitted to VAERS often lack details and sometimes contain errors.
  • Serious adverse events are more likely to be reported than mild side effects.
  • Rate of reports may increase in response to media attention and increased public awareness.
  • It is not possible to use VAERS data to calculate how often an adverse event occurs in a population.