UNC Health Talk

6 Things You Need to Know About Getting Your Second Dose of the COVID-19 Vaccines

The coronavirus disease 2019 (COVID-19) vaccines are now available to those who are eligible to receive them. Eventually, everyone who wants to be vaccinated will be able to do so, and it’s important to note that the COVID-19 vaccines currently available require two doses.

Here are six things you need to know about getting your second dose.

1. It is common for a vaccine to require two doses.

Several vaccines require multiple doses to receive maximum protection, including many you received as a child, such as diphtheria, tetanus, pertussis and measles vaccines.

“The first dose starts to build protection, and the second dose gives you the most protection the vaccine can offer. If you do not receive both doses of the currently available COVID-19 vaccines, you will not have the 95 percent effectiveness reported in the available data,” says UNC Health infectious disease expert Cynthia Gay, MD, MPH, who leads the Moderna clinical trial at UNC.

2. The timing of your second dose depends on which vaccine you received.

If you received the Pfizer vaccine, your second shot will be three weeks later (21 days). If you received the Moderna shot, your second shot will be four weeks later (28 days). You should try to get your second shot as close to 21 or 28 days after the first shot, depending on which vaccine you received.

However, a second dose is considered “valid” by the Centers for Disease Control and Prevention if it is received one to four days before the recommended timing of a second dose. In other words, if you receive the first dose of the Pfizer shot on Jan. 10, it is OK to receive your second shot Jan. 27-30. It is also acceptable to receive the second dose later than the recommended time. So if you receive the first dose of the Pfizer shot on Jan. 10, it is OK if you cannot get your vaccine exactly 21 days later.

3. You will make your appointment for your second dose of the vaccine at your first COVID-19 vaccine appointment.

The specific vaccine you receive will depend on what is available at the location where you receive your vaccine. You must receive the second dose from the same company (Pfizer or Moderna) as your first shot, so most vaccine clinics require you to receive your second dose at the same location where you received your first vaccine.

4. Second doses have been reserved for those scheduled to receive them.

Although the supply of vaccines is limited, vaccine sites usually maintain the appropriate supply of second doses for each week. Your second dose should be available when it is time for your appointment.

5. Side effects are more common with the second dose compared with the first dose.

Side effects can be more common after the second dose. However, side effects are usually mild or moderate and last only one to three days. In the trials of these vaccines, most people had no reactions to either the first or second dose, other than soreness at the site of the injection. If you have pain or discomfort, talk to your doctor about taking an over-the-counter medicine, such as ibuprofen or acetaminophen. Other mild side effects are not worrisome or unexpected and can reflect that the vaccine is working as intended to stimulate your immune system.

6. It is important to continue following all safety guidelines even after your second dose.

Regardless of whether you’ve had your first or second vaccine dose, you should continue to follow all of the recommended COVID-19 safety strategies (remaining in your household bubble, wearing a mask, practicing physical distancing, using good hand hygiene and disinfecting potentially contaminated surfaces) to protect your loved ones, co-workers and community.

“For some time after we get the vaccine, we will need to continue doing those things, because not everyone will get vaccinated,” Dr. Gay says. “Also, the vaccines are not 100 percent protective, and we don’t yet know if they will prevent asymptomatic infection.”

That means that while the vaccines are 95 percent effective at preventing symptomatic cases of COVID-19, we don’t yet know whether they prevent spreading the virus to others, even if you don’t have any symptoms.


Visit yourshot.org for the latest information on the COVID-19 vaccines.

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