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This has been reviewed and updated as of February 15, 2021.

Second COVID-19 Vaccine Dose

The COVID-19 vaccine is a major tool in helping to end the coronavirus pandemic. While Johnson & Johnson’s COVID-19 vaccine is expected to roll out soon as the only one-dose option, for the currently available Pfizer and Moderna vaccines, two doses are necessary to reach the vaccine’s full effectiveness.

With delays in vaccine rollouts to talk of more severe symptoms after the second dose, it can feel like the second booster shot remains more elusive than the first. If you are immunocompromised or at high-risk for severe outcomes from COVID-19, uncertainty about the second vaccine dose — and when you’ll be able to get it — can feel especially daunting.

Here are answers to all of your questions about planning for the second COVID-19 dose, what to do if your second dose gets delayed, and the precautions to take.

When to Get Your Second Dose of the Pfizer or Moderna COVID-19 Vaccine

The COVID-19 vaccine is administered via two doses intramuscularly (via the muscle in your arm):

  • Pfizer-BioNTech (30 µg, 0.3 ml each): 3 weeks (21 days) apart
  • Moderna (100 µg, 0.5 ml): 1 month (28 days) apart

The U.S. Centers for Disease Control and Prevention (CDC) says that the second dose of the vaccine should be administered as close to these recommended intervals as possible. However, the CDC’s guidance was recently updated to note that the second dose of the Pfizer and Moderna vaccines may be scheduled for administration up to six weeks (42 days) after the first dose if it is not feasible to adhere to the recommended interval.

“Researchers use clinical trial participants to try to identify when immune responses are really maximized with that second booster dose, so there’s a fair amount of wiggle room and it’s not a perfect science,” says Iahn Gonsenhauser, MD, Chief Quality and Patient Safety Officer at Ohio State University Wexner Medical Center in Columbus.

The updated CDC guidance comes as states continue to report vaccine shortages and rollout delays. By the end of January, nearly 50 million doses of the COVID-19 vaccines had been distributed to state and local governments — but only 31.1 million shots had been administered, per the CDC COVID Data Tracker. As of that time, only 5.6 million people had received two doses of the vaccine.

Although the CDC is not advocating for people to delay getting the second dose, you likely don’t have to worry if your second dose ends up getting scheduled beyond the recommended three- to four-week range.

“I think it’s best to stick as close to that recommended timeframe as possible if you’re able to,” says Dr. Gonsenhauser. “That said, many people will still develop a very robust immune response to the second booster shot, even if it’s given outside of the currently recommended time frame.”

Will You Have Lower Immunity If Your Second Dose Is Delayed?

You may be concerned that you’ll have less immunity if your second COVID-19 vaccine dose is delayed, especially if you’re in a high-risk group for COVID-19 complications.

However, compared to many other vaccines, the recommended time period between the COVID-19 vaccine doses is actually quite short. For instance, the two doses of the shingles vaccine Shingrix are separated by two to six months. Meanwhile, the Tdap vaccine (which protects againt tetanus, diptheria, and pertussis) requires a Td booster shot every 10 years and during pregnancy, per the CDC.

“I believe that the Pfizer and Moderna vaccine trials were designed to shorten the time between the first and second shot as much as possible, in order to confer immunity as soon as possible,” says Akiko Iwasaki, PhD, Professor of Immunology at Yale School of Medicine. “Twenty-one to 28 days is a very short timeline for a booster vaccine. Most booster vaccines are given with more time period in between.”

The booster shot is designed to activate your immune system’s memory cells, including memory B and T cells, that develop after the first immunization so you’re protected to the full extent possible — which usually takes weeks.

“It’s likely not only okay, but that delay in the second shot might actually be better for immunological boosting,” says Dr. Iwasaki. “So in the end, you might acquire an even better level and quality of immunity.” However, Dr. Iwasaki adds that this is a scientific insight from an immunological standpoint, not medical advice. It’s important to adhere to recommended CDC guidelines.

The bottom line is: You don’t have to worry too much if you can’t get your second dose in the recommended three to four weeks because of delays in vaccine rollouts or other issues out of your control.

If that’s the case, try to stay within the timeframe of six weeks recommended by the CDC.

Can You Get the Second COVID-19 Shot Early?

Because it takes a few weeks for your body to develop memory cells that the booster shot activates, you don’t want to get your booster shot too soon after the first dose.

“Normally with childhood vaccines, if you give the second dose too quickly, then it doesn’t count because it’s not stimulating the memory response,” says Dr. Iwasaki. “That’s when you actually have to redo it — not because it’s too late, but because it’s too early.”

There is one caveat: Second doses that are administered within a grace period of four days before the recommended date are still considered valid, per the CDC. Doses that are mistakenly administered earlier than that grace period should not be repeated.

When Would You Need to Retake the First COVID-19 Shot?

The CDC says you do not have to restart your vaccination series (meaning you take the first dose over again), even if you get the second dose beyond the six-week window. However, there is limited data on the efficacy of the vaccine beyond this time period.

“With the COVID-19 vaccine, we’re seeing quite a robust response to the first dose, with an increased response to the second dose,” says Dr. Gonsenhauser. “Because of that, as well as the tight supply of COVID-19 vaccines globally, I don’t anticipate they would recommend restarting the course until you’ve probably been a year out from your first booster.”

Experts still don’t know how often the COVID-19 course will need to be readministered — say, if it will need to be administered just once, or say, yearly, the way the flu vaccine is.

“It’s going to depend on how long the immune protection lasts from the vaccine itself, and it also will depend on what happens with COVID-19 in our community,” says Dr. Gonsenhauser. “If COVID-19 turns out to be a non-perpetual infection, unlike the flu, then there may not be a need for follow-up immunization.”

“However, if we see that COVID-19 is here to stay — which many of us suspect it will be — and it becomes a seasonal or cyclical infectious pathogen, that’s going to determine if it needs to be a more frequent vaccine. In that case, we would expect it to be a yearly vaccine, but that really remains to be seen,” he adds.

What If You Don’t Know Which Vaccine You Received First?

You should be informed by your health care provider which vaccine you receive during your first dose. However, in the rare occasion in which the first-dose vaccine can’t be determined or is no longer available, the CDC says any available mRNA COVID-19 vaccine may be administered at least 28 days after the first dose to complete the vaccination series.

If two doses of different vaccines are administered in these situations or by mistake, it’s not recommended that you receive additional doses of either vaccine.

What If You Get Infected with COVID-19 Between Vaccine Doses?

Because the vaccine doesn’t offer its full protection until a few weeks after the second dose is administered, it is still possible to get sick with COVID-19 between doses.

In the clinical trial that led to its authorization in the United States, the Pfizer vaccine had an efficacy rate of 52 percent after the first dose, per a December 2020 study published in the  New England Journal of Medicine.The Moderna vaccine provides around 80 percent efficacy one month after the first dose, per the U.S. Food & Drug Administration.

If you have a current coronavirus infection, your second vaccine dose should be deferred until you’ve recovered fully and you’ve met the CDC’s criteria to discontinue isolation.

There’s currently no data on the efficacy and safety of mRNA COVID-19 vaccines in people who received monoclonal antibodies or convalescent plasma as a part of their COVID-19 treatment.

However, based on the estimated half-life of these therapies (how long they work in the body) and evidence that suggests it’s uncommon for reinfection to occur in the 90 days after initial infection, the CDC says vaccination should be deferred for at least 90 days as a precautionary measure in this case (until more data is available). This is meant to avoid any potential interference of the antibody therapy with immune responses induced by the vaccine.

If you receive the therapy after your first dose but before the second dose, the second dose should also be delayed for at least 90 days following the therapy.

Note that these guidelines do not apply to antibody therapies not specific to COVID-19 treatment, such as intravenous immunoglobulin or RhoGAM.

Should You Stop Immunosuppressant Medication After the Second COVID-19 Vaccine Dose?

There is good reason to think that COVID-19 vaccines will not work as well in people who take medication that affects immune system function.

However, that doesn’t mean that the COVID-19 vaccine doesn’t work — it may just work less well than in people who don’t take these medications. But even a slightly less effective vaccine may still help prevent severe disease that requires hospitalization (or worse).

That said, some doctors and medical organizations are recommending that people who take certain medications temporarily stop them after getting the vaccine in order to try to help improve the body’s response to the vaccine.

The American College of Rheumatology recently recommended that some patients can stop taking methotrexate and JAK inhibitors [such as tofacitinib (Xeljanz), baricitinib (Olumiant), and upadacitinib (Rinvoq)] for one week after each vaccine dose. They also made other recommendations about timing when you get the COVID-19 vaccine in the course of treatment with biologics rituximab (Rituxan) and abatacept (Orencia). However, the guidance says that patients should not stop taking most medications before or after getting the vaccine. This is because there is no reason to think, based on available data, that stopping these medications would increase your body’s immune system response to the vaccine.

You can read more about these recommendations here.

Keep in mind that they are meant to be individualized to each patient and are not universal advice. For example, some experts do not recommend patients temporarily stop medication because they may have concerns that patients could flare if they stop taking it, or are not as worried about the potential decrease in vaccine effectiveness.

Expect More Severe Symptoms with the Second Dose of the COVID-19 Vaccine

As with the first dose of the COVID-19 vaccine, you should expect post-vaccination symptoms such as pain and swelling at the injection site and fatigue, headache, fever, and chills. Most systemic post-vaccination symptoms are mild to moderate in severity and appear within the first three days of vaccination, resolving within one to three days.

They are more frequent and severe following the second dose, per the CDC.

“This happens when you have an already high antibody response [from the first vaccine dose] and then you get the second shot, because these antibodies can attack the cells that are presenting the antigen,” says Dr. Iwasaki.

In other words, the stronger reaction to the second vaccine is a sign that your body is getting better prepared to recognize and fight off coronavirus germs.

Post-vaccine side effects are also more common among younger people compared to older people, because the immune system generally has a weaker response to vaccines with age.

Unless you develop a contraindication to the first dose — such as an immediate allergic reaction (more on this later) — the CDC says you should complete the vaccine series to optimize your protection against COVID-19, even if you develop some local or systemic symptoms.

If it’s possible, consider taking the day off after you receive your booster shot.

“Given how many people are having symptoms following their second dose, I would recommend being prepared to need to take time off, or at least potentially take a slow day, the day after you receive the second dose,” says Dr. Gonsenhauser. “From my personal experience, I wasn’t able to work the day after my second dose. I had pretty significant body aches, chills, fever, and a lot of fatigue.”

However, Dr. Gonsenhauser notes that his symptoms completely resolved after 24 hours.

“I’ve had very few patients who have had both vaccine doses, but I haven’t had anybody who has communicated with me after the second vaccine dose, so I’m assuming that is good news,” says Lynn Ludmer, MD, Medical Director of Rheumatology at Mercy Medical Center in Baltimore. “However, as a health care provider having had both doses and seeing colleagues who have had second doses, many people have symptoms.”

Dr. Ludmer notes that after her second dose, she did experience symptoms, but was able to work the next day.

“It’s important to get that second dose, but to be prepared that you may not feel well so you’re not worried about it,” says Dr. Ludmer. “A lot of people compare it to getting the Shingrix vaccine, where they may have worse symptoms after the second dose.”

Dr. Ludmer adds that the symptoms may be a small price to pay for avoiding coronavirus.

“Even though it can be uncomfortable to have side effects, it’s probably a good sign because it means your body is recognizing the vaccine as foreign, and that’s the goal we try to accomplish with vaccines: that the body recognizes something is foreign and tries to fight it off,” she adds.

How to Handle Side Effects After Your Second COVID-19 Vaccine Dose

As mentioned above, prepare to take a day off or “slow day” if possible the day after receiving the second dose — since you may be more likely to experience symptoms.

You should receive COVID-19 vaccination record cards after each dose of the vaccination. Bring that card to your appointment for the second dose and make backup copies by taking a photo on your phone or scanning it.

“That’s going to become quite important as we work toward normalizing again,” says Dr. Gonsenhauser. “I think people are going to have to potentially provide documentation of both courses of their vaccine in the foreseeable future as we resume more normal activities.”

The common vaccine side effects that you might experience apply to both doses of the vaccines.

  • In the arm where you got the vaccine (local side effects):
    • Pain
    • Swelling
  • Throughout the rest of the body (systemic side effects):
    • Fever
    • Chills
    • Tiredness
    • Headache

If you have pain or discomfort after getting the vaccine, the CDC recommends talking to your doctor about taking an over-the-counter medicine such as ibuprofen or acetaminophen. It is not advised to taking these preventively before getting the vaccine. You can also apply a clean, cool, wet washcloth over the area where you got the shot or exercise your arm to reduce pain and discomfort.

Drink plenty of fluids and dress lightly if you have a fever. Fever and pain are normal in most cases, but contact your doctor or health care provider if redness or tenderness at the injection site increases after 24 hours or if your side effects are worrying or don’t go away after a few days.

You can also sign up for v-safe, the CDC’s smartphone-based tool that uses text messages and web surveys to provide personalized health check-ins after you receive your COVID-19 vaccine. Use it to quickly report any side effects, and depending on your responses, someone from CDC may call you to get more information.

Even if you have non-allergic side effects after the first shot, you should get the second shot. If you’re having trouble differentiating between a disease flare-up (from your autoimmune condition) and vaccine side effects, talk to your doctor.

Monitor for Potential Allergic Reactions

If you had an immediate allergic reaction after receiving the first dose of an mRNA COVID-19 vaccine, you should not receive the second dose, per the CDC.

The CDC considers the following contraindications to receiving the COVID-19 vaccine:

  • Severe allergic reaction (such as anaphylaxis) after a previous dose of an mRNA COVID-19 vaccine or any of its components
  • Immediate allergic reaction of any severity to a previous dose of an mRNA COVID-19 vaccine or any of its components (including polyethylene glycol [PEG])*
  • Immediate allergic reaction of any severity to polysorbate (due to potential cross-reactive hypersensitivity with the vaccine ingredient PEG)*

* If you fall into the categories, you should not receive mRNA COVID-19 vaccination (Pfizer-BioNTech or Moderna) at this time unless you have been evaluated by an allergist-immunologist and it is determined that you can safely receive the vaccine — such as under observation, in a setting with advanced medical care available, etc.

An immediate allergic reaction means it occurred within four hours of vaccination, and may include symptoms such as hives, swelling, or wheezing (respiratory distress), per the CDC.

Hypothetically, it’s possible you wouldn’t experience a potential allergic reaction until the second dose of the COVID-19 vaccine, but data is needed to confirm if allergic reactions are more likely to occur after the second dose is administered.

“It generally takes an exposure to something one time and then a second exposure to have an anaphylactic response,” says Dr. Gonsenhauser. “So if you happen to be predisposed to, say, an allergic reaction to PEG but you’ve never come in contact with it prior to the first dose of the vaccine, the second dose may trigger an allergic response — but it it’s extremely rare and we’ve really not seen increased anaphylactic responses to second COVID-19 doses to support that.”

As with the first dose of the vaccine, you should be observed after your shot at the vaccination site.

If you have a history of an immediate allergic reaction of any severity to a vaccine or injectable therapy or a history of anaphylaxis due to any cause, you should be observed for 30 minutes. Otherwise, you should be observed for 15 minutes.

Read more about if you should get the COVID-19 vaccine if you have a history of allergic reactions and what to know about the COVID-19 vaccine if you have allergies to injectable or infused medication.

Continue to Take Precautions After Your Second COVID-19 Vaccine Dose

Remember that you won’t instantly be protected after your second dose of the vaccine. It takes two weeks after you get your second dose of the vaccine to be considered to be fully vaccinated. Congratulations! While this isn’t permission to start resuming “normal” pre-pandemic life, the CDC recently said that once you are fully vaccinated, you no longer need to quarantine if you’re exposed to someone with COVID-19. You have to meet this criteria:

  • Are fully vaccinated (≥2 weeks following receipt of the second dose in a 2-dose series, or ≥2 weeks following receipt of one dose of a single-dose vaccine)
  • Are within 3 months of receiving of the last dose in the series
  • Have no symptoms of COVID-19 since being exposed

If you don’t meet the criteria (say, it’s been more than three months since your vaccine dose), you would still need to quarantine if exposed to COVID-19. If you have symptoms of COVID-19, you should be evaluated and tested.

It’s also essential to continue practicing mitigation tools to stop the spread of the virus until we learn more about how COVID-19 vaccines work in real-world conditions.

“It feels incredibly liberating to receive your first and then also your second dose of vaccine, but we have to make sure that we temper that feeling a little bit and we don’t let our guard down,” says Dr. Gonsenhauser. “We still have a lot of work to do. Even if we’re vaccinated, we still don’t really know if that prevents us from spreading and transmitting a virus that can hitch a ride on us — even if it doesn’t make us sick.”

This is especially important as we continue to learn more about new coronavirus variants and whether they decrease the effectiveness of the vaccines.

The general guidance to follow is simple, yet not always easy to adhere to:

  • Maintain a social distance of six feet or more from people outside of your household whenever possible.
  • Wear face coverings when out in public and when you can’t be socially distant.
  • Wash or sanitize your hands frequently and disinfect commonly touched surfaces.
  • Avoid large groups or situations when it will be hard to be socially distant.
  • When spending time with others, being outdoors is safer than indoors.

Even as you continue to follow these efforts, take some comfort in knowing that your being fully vaccination is helping to bring us one step closer to slowing down the COVID-19 pandemic.

“Be prepared for your second dose and be excited that we are moving toward returning our lives to a little bit more of a semblance of normal,” says Dr. Gonsenhauser.

Read more about what to do after receiving the COVID-19 vaccine if you’re immunocompromised or have an autoimmune condition.

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COVID-19 Vaccinations in the United States. COVID Data Tracker. U.S. Centers for Disease Control and Prevention. Accessed January 31, 2020. https://covid.cdc.gov/covid-data-tracker/#vaccinations.

COVID-19 Vaccine Clinical Guidance Summary for Patients with Rheumatic and Musculoskeletal Disease. American College of Rheumatology. February 8, 2021. https://www.rheumatology.org/Portals/0/Files/COVID-19-Vaccine-Clinical-Guidance-Rheumatic-Diseases-Summary.pdf.

Discontinuation of Isolation for Persons with COVID-19 Not in Healthcare Settings. COVID-19. U.S. Centers for Disease Control and Prevention. December 3, 3030. https://www.cdc.gov/coronavirus/2019-ncov/hcp/disposition-in-home-patients.html.

Information about the Pfizer-BioNTech COVID-19 Vaccine. COVID-19. U.S. Centers for Disease Control and Prevention. January 25, 2021. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/Pfizer-BioNTech.html.

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Interview with Akiko Iwasaki, PhD, Professor of Immunology at Yale School of Medicine

Interview with Iahn Gonsenhauser, MD, Chief Quality and Patient Safety Officer at Ohio State University Wexner Medical Center

Interview with Lynn Ludmer, MD, Medical Director of rheumatology at Mercy Medical Center in Baltimore

Polack FP, et al. Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. The New England Journal of Medicine. December 31, 2020. doi: http://dx.doi.org/10.1056/NEJMoa2034577.

Shingles Vaccination. Vaccines and Preventable Diseases. U.S. Centers for Disease Control and Prevention. January 25, 2018. https://www.cdc.gov/vaccines/vpd/shingles/public/shingrix/index.html.

U.S. Food & Drug Administration. Vaccines and Related Biological Products Advisory Committee Meeting. December 17, 2020. https://www.fda.gov/media/144434/download.

V-safe After Vaccination Health Checker. COVID-19. U.S. Centers for Disease Control and Prevention. January 27, 2021. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/vsafe.html.

What Vaccines are Recommended for You. Vaccine Information for Adults. U.S. Centers for Disease Control and Prevention. https://www.cdc.gov/vaccines/adults/rec-vac/index.html.

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