Getting vaccinated against COVID-19 is one of the best ways to protect yourself and others from the disease. All COVID-19 vaccines authorized for use in the United States have been proven safe and effective at preventing serious illness, hospitalization and death. But you may have heard that after getting your shot, you need to wait 15 minutes before leaving the vaccination site. Here’s a look at why that recommendation exists and whether it’s truly necessary.
Why the 15-minute waiting period?
After any vaccination, you’re advised to wait 15 minutes before leaving the clinic, doctor’s office or other site where you received your shot. This waiting period allows vaccination providers to monitor you for immediate adverse reactions, which are rare but can occur with any vaccine.
For example, in the past, a small number of people have experienced severe allergic reactions (anaphylaxis) after receiving certain vaccines. Anaphylaxis requires immediate treatment with epinephrine (adrenaline). The COVID-19 vaccines can also cause anaphylaxis in rare cases, although at a very low rate of around 2 to 5 people per million vaccinated.
The most common symptoms of anaphylaxis include:
- Skin reactions like hives, itching or flushed skin
- Swelling of the lips, face and throat
- Breathing difficulties like wheezing, coughing or shortness of breath
- A fast heart rate
- Dizziness or weakness
- Nausea and vomiting
Anaphylaxis typically begins within minutes to hours after vaccination. By having people wait 15 minutes before leaving, clinic staff can rapidly treat anaphylaxis or any other immediate reactions if necessary.
Are severe allergic reactions common after COVID-19 vaccines?
Severe allergic reactions like anaphylaxis can occur after any vaccine but are overall very rare. Research shows that anaphylaxis occurs after around 1.3 of every 1 million doses of flu vaccine given. Rates so far for COVID-19 vaccines are slightly higher than for flu shots:
| Vaccine | Estimated rate of anaphylaxis |
| Pfizer-BioNTech | 4.7 per million doses administered |
| Moderna | 2.5 per million doses administered |
| Johnson & Johnson | 3.4 per million doses administered |
Although the mRNA vaccines (Pfizer and Moderna) appear to have higher rates, anaphylaxis is still very uncommon. Over 219 million Americans have received at least one COVID-19 vaccine dose, but there have been only 1,245 confirmed cases of anaphylaxis afterward, as of late February 2021.
People who have had an anaphylactic reaction to any vaccine or injectable medication in the past are advised to wait 30 minutes after getting their COVID-19 shot for closer monitoring.
What are the other potential side effects?
Aside from rare anaphylaxis, some other common side effects can also start within minutes to hours of getting vaccinated. According to the CDC, these temporary reactions are normal signs that your body is building protection against COVID-19. They include:
- Pain, redness or swelling at the injection site
- Tiredness
- Headache
- Muscle or joint pain
- Chills
- Fever
- Nausea or vomiting
In clinical trials, most of these reactions were mild to moderate in severity and resolved within 1-3 days. If you experience any concerning symptoms after vaccination, call your doctor. But in most cases, these side effects don’t require emergency care and are no cause for alarm.
Can you have an allergic reaction even after 15 minutes?
Anaphylaxis after COVID-19 vaccination can technically occur outside of the standard 15-minute observation window – but it’s very unlikely. In one U.S. study looking at over 1.8 million vaccine doses:
- 99.9% of anaphylaxis cases occurred within 15 minutes
- The median time to symptom onset was 13 minutes
- No cases occurred more than 45 minutes after vaccination
A few isolated cases of anaphylaxis occurring hours after vaccination have been reported. But this is extremely rare, and in some instances may have been coincidental. Regardless, any concerning symptoms should be evaluated by a healthcare professional to rule out other potential causes besides the vaccine.
Are there exceptions to the 15-minute waiting period?
Certain groups may not need to wait the full 15 minutes before leaving after their COVID-19 shot. According to CDC guidelines, the following groups can consider waiting just 10-15 minutes if they have no symptoms:
- People who have had no immediate reactions to any vaccine or injectable therapy in the past
- People who aren’t worried about having a reaction after vaccination
And the following groups may not need to wait at all after COVID-19 vaccination if they feel well:
- People who need to leave right away due to work, childcare or other obligations
- Teens aged 16-17 years old
These allowances apply as long as you have no history of severe allergic reactions and no symptoms. However, the standard 15-minute wait is still recommended when possible for optimal safety monitoring.
Can you have an allergic reaction days later?
It’s very rare to have a first-time allergic reaction to a vaccine more than 4 hours after the shot. In the CDC safety monitoring study mentioned earlier, there were no reports of anaphylaxis after day one of vaccination.
Some people do experience other delayed side effects in the days following vaccination, like:
- Fatigue
- Headache
- Muscle/joint aches
- Fever
- Chills
- Nausea
These typically resolve within 1-3 days. If symptoms persist or you have concerns, call your doctor. But these delayed reactions are not considered severe or dangerous.
The takeaway
Here are some key points about waiting after your COVID-19 vaccine:
- The 15-minute waiting period allows providers to monitor for rare but serious allergic reactions like anaphylaxis.
- Anaphylaxis almost always occurs within 15 minutes if it happens.
- Other common side effects may also begin in the waiting period.
- Some groups like teens may be able to leave sooner than 15 minutes if they feel well.
- Delayed side effects can occur later, but are not severe allergic reactions.
- Call 911 or seek emergency care if you have serious symptoms of anaphylaxis at any time after vaccination.
While anaphylaxis and other reactions are rare, the 15-minute observation window acts as an important safety net. Following vaccination best practices helps make sure that COVID-19 shots remain very low risk for the public.
Ultimately, the likelihood of having a severe reaction is far lower than the dangers of COVID-19 itself for most people. Hundreds of millions of doses have been safely administered worldwide. Vaccination continues to be a leading way to control the pandemic and prevent the most tragic outcomes of the disease.