Skip to main content

Is One Vaccine Dose Enough After COVID-19 Infection?

Posted on by Dr. Francis Collins

COVID-19 vaccination record card
Credit: iStock/Bill Oxford

For the millions of Americans now eligible to receive the Pfizer or Moderna COVID-19 vaccines, it’s recommended that everyone get two shots. The first dose of these mRNA vaccines trains the immune system to recognize and attack the spike protein on the surface of SARS-CoV-2, the virus that causes COVID-19. The second dose, administered a few weeks later, boosts antibody levels to afford even better protection. People who’ve recovered from COVID-19 also should definitely get vaccinated to maximize protection against possible re-infection. But, because they already have some natural immunity, would just one shot do the trick? Or do they still need two?

A small, NIH-supported study, published as a pre-print on medRxiv, offers some early data on this important question [1]. The findings show that immune response to the first vaccine dose in a person who’s already had COVID-19 is equal to, or in some cases better, than the response to the second dose in a person who hasn’t had COVID-19. While much more research is needed—and I am definitely not suggesting a change in the current recommendations right now—the results raise the possibility that one dose might be enough for someone who’s been infected with SARS-CoV-2 and already generated antibodies against the virus.

These findings come from a research team led by Florian Krammer and Viviana Simon, Icahn School of Medicine at Mount Sinai, New York. The researchers reasoned that for folks whose bodies have already produced antibodies following a COVID-19 infection, the first shot might act similarly to the second one in someone who hadn’t had the virus before. In fact, there was some anecdotal evidence suggesting that previously infected people were experiencing stronger evidence of an active immune response (sore arm, fever, chills, fatigue) than never-infected individuals after getting their first shots.

What did the antibodies show? To find out, the researchers enlisted the help of 109 people who’d received their first dose of mRNA vaccines made by either Pfizer or Moderna. They found that those who’d never been infected by SARS-CoV-2 developed antibodies at low levels within 9 to 12 days of receiving their first dose of vaccine.

But in 41 people who tested positive for SARS-CoV-2 antibodies prior to getting the first shot, the immune response looked strikingly different. They generated high levels of antibodies within just a few days of getting the vaccine. Compared across different time intervals, previously infected people had immune responses 10 to 20 times that observed in uninfected people. Following their second vaccine dose, it was roughly the same story. Antibody levels in those with a prior infection were about 10 times greater than the others.

Both vaccines were generally well tolerated. But, because their immune systems were already in high gear, people who were previously infected tended to have more symptoms following their first shot, such as pain and swelling at the injection site. They also were more likely to report other less common symptoms, including fatigue, fever, chills, headache, muscle aches, and joint pain.

Though sometimes it may not seem like it, COVID-19 and the mRNA vaccines are still relatively new. Researchers haven’t yet been able to study how long these vaccines confer immunity to the disease, which has now claimed the lives of more than 500,000 Americans. But these findings do suggest that a single dose of the Pfizer or Moderna vaccines can produce a rapid and strong immune response in people who’ve already recovered from COVID-19.

If other studies support these results, the U.S. Food and Drug Administration (FDA) might decide to consider whether one dose is enough for people who’ve had a prior COVID-19 infection. Such a policy is already under consideration in France and, if implemented, would help to extend vaccine supply and get more people vaccinated sooner. But any serious consideration of this option will require more data. It will also be up to the expert advisors at FDA and Centers for Disease Control and Prevention (CDC) to decide.

For now, the most important thing all of us can all do to get this terrible pandemic under control is to follow the 3 W’s—wear our masks, wash our hands, watch our distance from others—and roll up our sleeves for the vaccine as soon as it’s available to us.


[1] Robust spike antibody responses and increased reactogenicity in seropositive individuals after a single dose of SARS-CoV-2 mRNA vaccine. Krammer F et al. medRxiv. 2021 Feb 1.


COVID-19 Research (NIH)

Krammer Lab (Icahn School of Medicine at Mount Sinai, New York, NY)

Simon Lab (Icahn School of Medicine at Mount Sinai)

NIH Support: National Institute of Allergy and Infectious Diseases


  • Susan Via says:

    I donated a kidney to my now 84 year old husband 4 years ago. He is doing great and received second Moderna dose two weeks ago. My second dose is today. I had fever, terrible chills and headache for two days after my first dose, he had nothing but a sore arm after both doses an dfatigue after second dose. Of course he is on immunosuppressants and we cannot find much information on the effectiveness of the vaccine on solid organ transplant recipients. What is the most current data for them? Any ongoing studies? He is a retired MD and would be happy to volunteer.

  • Maryann says:

    I’m a 74 year old woman who had a lobectomy last year for a non small cell tumor. My CT scans are now clear. I had the 1st Pfizer vaccine on Jan 22, 2021 and the 2nd on Feb 9, 2021. I have had 2 qualitative antibody tests this week and both were negative for antibodies. Has anyone else had this experience?

    • maryann says:

      I just received an answer to my own question. Apparently it is perfectly normal for vaccine receivers to get a negative antibody response because the protein that covid has is known as ‘N’ protein, whereas the protein that the vaccine carries is known as a ‘spike’ protein and therefore it doesn’t register an antibody response. So, briefly, it means that a negative antibody response on the antibody test that is given after two doses of vaccine is perfectly normal. YAY!

    • Linda G. says:

      I received my first Pfizer vaccine on 1/25/21. No reactions. On Feb. 5, l tested positive. I was hospitalized from 2/13-2/17. While in the hospital, l received the five dose course of Ramdesevir and Dexamethazone. The CDC said l needed to wait 90 days to do anything, which eliminated all the recommendations for the time frame between vaccine 1 and 2. Subsequently l have spoken to NY State, the CDC several times and Pfizer. They claim no research is being done on this particular situation. I have made a vaccination appointment for May 13. Do l start from dose one? Just get dose 2? The only solid answer l did receive was that Pfizer said DO NOT GET ANYTHING BUT PFIZER. Any science or medical based info would be very helpful.

  • simone a. says:

    I had symptoms I thought were due to the flu (extremely painful body aches, chills, fatigue, some fever – not much- for a full week) then, when I got the Covid-19 vaccine two weeks later (on Feb 11) I had again the same symptoms and I also vomited…on the carpet, I couldn’t hold it. Which had never happened before. The symptoms lasted only 24 hours this time. My doctor insisted I have had the flue previously. I insisted to get an antibody test. The test revealed I had had Sars cov2. (I had the blood test on feb 25, the results today), Now I am not sure if I should have the second vaccine; I fear it would be too much for my immune system. I might take some tylenol before the second vaccine (March 11). It seems that doctors don’t know much about it. By the way I am a teacher, I teach in person … and I am 75 years old. Born on August, 24th, 1945.

  • simone amselli says:

    I have family living in Israel. As this country is closely monitoring the Covid vaccines, and started administering the vaccines well before we did, I contacted my family. The answer I just received was: the persons who had contracted the virus and had the first vaccines, have been asked to wait 90 days before the second one. One person in particular ( a member of my family) who had the second vaccine after the 90 days had a very small reaction then.

  • Herpezine says:

    It is an interesting approach to take and you would expect that natural immunity will give you.

  • Loulou F. says:

    After two doses of the Pfizer vaccine, my antibody test is negative. Do I have protection?

  • Diana J. says:

    I had my first shot of moderna Gad. I had side effects. I got a second one on feb 8th and on the second day I had a small fever and chills. days after I got a severe rash on Both arms neck back and chest then they fade away turn light brown and stay in my skin light freckles then it starts over again with the rash most every day two weeks ago I noticed two big lumps on top of my clavicle the left one is very very painful I went to my md he said he did t know much I asked him to draw a CBC to see if I had an infection from it because I had heard of a doc getting the shots with the same thing I have and passed away 14 days later of brain bleeding I’m very scarred also my pulse has been very fast that I’m taking motropolol ans it does not even help it feels like I’m having a heart attack my heart pounds very fast can anyone please help me please?

    • Omar says:

      I’ve been hearing that the rash has been noted as possible rare side effect to the vaccine, and I understand it is harmless and should subside with a little patience. The heart rate, I would argue is anxiety. All the best.

  • Amy Cartwright says:

    Very specific and informative! Thanks for sharing this helpful content! Regards

  • Shirley J. says:

    Question. Should you get the second vaccine if you contracted Covid infection one day after first dpshot. Exposed at work. Not from shot

  • Ken Cole says:

    I caught something severe at a large meeting in San Francisco (30,000+ from all over the globe including China) the week of December 14, 2019. It resulted in a week in bed with severe fatigue and a persistent cough. The fatigue gradually subsided over the next couple of months while the cough persisted for 6-8 months.

    After my first Dose of Moderna Vaccine on Feb 15, 2021, I developed severe muscle spasms and cramps on day 3 – 6 along with fatigue. The fatigue subsided after 16 days. Now I am afraid of getting the second shot as it likely will produce an even stronger reaction.

    • Lisa says:

      I also had similar side effects and fatigue for over 10 days but heard the 2nd dose is either similar or a little less, not worse

    • Lisa says:

      I’m curious how your 2nd vaccine side effects are as I also had 10 plus days of fatigue and last March had a virus with similar symptoms but never had antibodies or was even able to get a Covid test back then

  • MRKRUSS says:

    Today is 3/9/2021 and we await our next Stimulus Check from the Government. If the cost is $46.00 for the Modena Vaccination—-Isn’t it far more important to have the Vaccination, then the Big Car or the Fancy Meal? Where are our Priorities as a Country? Our News Stations are Bombarding us with the next Scandal and we don’t focus in on having Healthy Lives. We worry about the Sensationalism and we Forget that we had one of the Greatest Achievements of our Lifetimes—-A Vaccination for the Corona Virus that is 94—95% Affective. Isn’t it time that we see the Best rather then the Worst? Isn’t it time that we Sober Up to our Addiction to the Negative News. Isn’t it time that we get on our Knees and thank the Medical Community, that within record time came up with Cures for one of the Deadliest Plagues of your Lifetime?

  • Kathleen L. says:

    On February 4, 2021 I received my first Pfizer shot. On February 10, I began to have Covid symptoms. On February 15 i tested positive for Covid. On February 16, I received a monoclonal infusion. When should I have my 2nd Pfizer shot?

  • Jacklynn swartz says:

    I have covid right now for the 2nd time. First time was about 1 week shy of a year ago.

  • Annie Hoffman says:

    I had Moderma shot #1 yesterday 3/10/21. I did have and recovered from COVID in December. Well my fever went as high as 102.1 and I had lots of aches throughout my body. I was also fatigued. I’m hoping dose 2 isn’t the same. I had to take 2 days off work. 🙁

  • Shirley T. says:

    I had covid all the usual symptoms I got my first shot of covid vaccine after symptoms of swollen arm and pain also coughing running nose now my problem and i am confused if I should take the second shot

  • Martha says:

    Thank you for sharing this information. I had Covid in December and received the first Pfizer dose on March 10. I had chills, slight fever, and nausea. I think I felt even worse than when I had the virus lol. I heard that most of the people have reactions after the 2nd dose, but now I have a better understanding of why I had them after the first one. I hope I won’t have these reactions after the 2nd one. Definitely, more research is needed.

    • Linda L says:

      I was apprehensive about getting my second Pfizer on March 9 after having a rough time with the first one, which I described here. Fortunately, my reaction this time was less intense. I had been told to expect the same or worse reaction the second time around.

    • Carlton says:

      I am 61 years old. I contracted covid in mid November and I had every symptom except for loss of smell & taste. I received my first Pfizer dose on March 10th. Several hours later my arm became very sore. I had swelling and a large bruise at the injection area. My arm is finally back to normal after 5 days. I also had a light headache and a touch of fatigue which only lasted for a few hours. I think the CDC has established a grace period of 90 days for those with natural immunity to receive Covid vaccine, which is not long enough. Also, medical data is indicating that one dose of Pfizer or Moderna can produce more antibodies (10-fold) in previous infected people compared to 2 doses for people who never been infected. I am considering pushing by second dose out an additional week. This will still keep me within CDC protocol. I wish I had waited at least 6 months from the time of contracting Covid to receiving my first vaccine dose.

  • Holly H. says:

    My husband and I have both had COVID back in Mid January. We are both over 65 but in great shape. We were not hospitalized and did ok. It really took 17 days for us to feel sort of back to normal. We had completely different symptoms when infected with the VIRUS. An important note, my husband had complete knee replacement on Dec. 9th 2020. The virus gave him great knee pain.
    Yesterday, March 13th we got our first vaccine of Moderna at 10:00 am. We felt fine for 13 hours and then at 1:00 am we both woke up with horrible chills and body aches. It really hit his back, and his knee with bad aches. My hands I could hardly move.and I am a competitive tennis player and do YOGA regularly. . We are living examples of what this article talks about. If you have had the virus then you very well likely get hit with more painful symptoms then the person who has not had the virus.

    • Linda L says:

      With the virus and with the first Pfizer dose I had terrible muscle and joint pains, especially painful in my back (I have had two lumbar fusion surgeries) and my one knee that will require replacement at some point. It’s as if the virus and vaccines find the weak spots.

    • Ken says:

      Holly: Your husband’s story sounds very similar to mine. I am over 65, but physically active to an unusual amount. By day 3 after my vaccine, all of my back muscles went into a static clench, then it spread to my hips and thighs. I had to spend three days on the couch to be able to stand upright again. I can strain my back one or two times a year, but never with such a severity, and then with two weeks of fatigue thrown on top of it. I am glad I got the first shot. But am not planning on the second until I see definitive science showing that the second shot is required for people in our situation.

  • Guillermo S. says:

    I am56. Had the Pfizer vaccine 7 days ago. No issues. A little soreness in my arm at the injection site (like I get with every shot I’ve taken). Super excited that I will soon be immune and able to see my father, mother, brother, sisters and friends again!

    • Sally Hodges says:

      60 year old female. I had Covid 19 early January. My first Pfizer shot was March 12. Ten hours later I had severe nausea and vomiting, extreme light headedness, chills and joint pain. I’m concerned about getting the second doze.

      • Holly H. says:

        I hear you Sally. My husband and I had the same issue. I am finally feeling better after 48 hours from our Moderna shot.
        We did have Covid back in mid January. So I figured that’s why we felt so poorly after 12 hours from the vaccination. Our bodies had the antibodies that are fighting the virus in the vaccine.

  • Dix says:

    I had COVID November 12 for 10-12 days was able to stay home. Got Pfizer vaccine on March 12, had sore arm first then neck pain and headaches, chills, low temp, muscle pain, diarrhea, runny nose. I am still having periods of weakness and dizziness on March 15. I don’t want to get second vaccine on Good Friday in three weeks and have miserable Easter. Can I wait longer for second dose or even skip it all together?

    • Omar says:

      Some countries are opting to give only one dose to people who were previously infected, and I was told by a doctor today that there should be no adverse effects from doing so. I had COVID in Aug, and I received one dose of Pfizer. I only had a sore arm, and they are refusing to give me a second dose. Ridiculous, if you ask me. The fact that you had the reaction you did to the first dose means you had a nice immune reaction to it, so you just got yourself a nice boost if you opt to discontinue. Certainly consult your doctor, but me personally, if I could get two, I would. That’s what the studies were based on. And that’s the guidance from the folks that made it. I would rather have side effects from a vaccine than COVID. Good luck.

  • John A. says:

    i had the covid back in oct 2020 got my first shot moderna in feb 18 2021 i got very sick from it first my lower back witch keep me from sleeping the first night the second day i have headache high temp and uncontrollable witch body shakes witch i was freezings my body temp went to 105 went to hospital the doctors didn’t seem to have the answers to this because this is so new they said the second shot is worse than the first don’t want to put my body threw this again

  • 1 2 3 4 5

Leave a Reply to DianeCancel reply