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Two Studies Show COVID-19 Antibodies Persist for Months

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Antibodies against SARS-CoV-2
Caption: Artistic rendering of SARS-CoV-2 virus (orange) covered with antibodies (white), generated by an immune B cell (gray) at the bottom left. Credit: iStock/selvanegra

More than 8 million people in the United States have now tested positive for COVID-19. For those who’ve recovered, many wonder if fending off SARS-CoV-2—the coronavirus that causes COVID-19—one time means their immune systems will protect them from reinfection. And, if so, how long will this “acquired immunity” last?

The early data brought hope that acquired immunity was possible. But some subsequent studies have suggested that immune protection might be short-lived. Though more research is needed, the results of two recent studies, published in the journal Science Immunology, support the early data and provide greater insight into the nature of the human immune response to this coronavirus [1,2].

The new findings show that people who survive a COVID-19 infection continue to produce protective antibodies against key parts of the virus for at least three to four months after developing their first symptoms. In contrast, some other antibody types decline more quickly. The findings offer hope that people infected with the virus will have some lasting antibody protection against re-infection, though for how long still remains to be determined.

In one of the two studies, partly funded by NIH, researchers led by Richelle Charles, Massachusetts General Hospital, Boston, sought a more detailed understanding of antibody responses following infection with SARS-CoV-2. To get a closer look, they enrolled 343 patients, most of whom had severe COVID-19 requiring hospitalization. They examined their antibody responses for up to 122 days after symptoms developed and compared them to antibodies in more than 1,500 blood samples collected before the pandemic began.

The researchers characterized the development of three types of antibodies in the blood samples. The first type was immunoglobulin G (IgG), which has the potential to confer sustained immunity. The second type was immunoglobulin A (IgA), which protects against infection on the body’s mucosal surfaces, such as those found in the respiratory and gastrointestinal tracts, and are found in high levels in tears, mucus, and other bodily secretions. The third type is immunoglobulin M (IgM), which the body produces first when fighting an infection.

They found that all three types were present by about 12 days after infection. IgA and IgM antibodies were short-lived against the spike protein that crowns SARS-CoV-2, vanishing within about two months.

The good news is that the longer-lasting IgG antibodies persisted in these same patients for up to four months, which is as long as the researchers were able to look. Levels of those IgG antibodies also served as an indicator for the presence of protective antibodies capable of neutralizing SARS-CoV-2 in the lab. Even better, that ability didn’t decline in the 75 days after the onset of symptoms. While longer-term study is needed, the findings lend support to evidence that protective antibody responses against the novel virus do persist.

The other study came to very similar conclusions. The team, led by Jennifer Gommerman and Anne-Claude Gingras, University of Toronto, Canada, profiled the same three types of antibody responses against the SARS-CoV-2 spike protein, They created the profiles using both blood and saliva taken from 439 people, not all of whom required hospitalization, who had developed COVID-19 symptoms from 3 to 115 days prior. The team then compared antibody profiles of the COVID-19 patients to those of people negative for COVID-19.

The researchers found that the antibodies against SARS-CoV-2 were readily detected in blood and saliva. IgG levels peaked about two weeks to one month after infection, and then remained stable for more than three months. Similar to the Boston team, the Canadian group saw IgA and IgM antibody levels drop rapidly.

The findings suggest that antibody tests can serve as an important tool for tracking the spread of SARS-CoV-2 through our communities. Unlike tests for the virus itself, antibody tests provide a means to detect infections that occurred sometime in the past, including those that may have been asymptomatic. The findings from the Canadian team further suggest that tests of IgG antibodies in saliva may be a convenient way to track a person’s acquired immunity to COVID-19.

Because IgA and IgM antibodies decline more quickly, testing for these different antibody types also could help to distinguish between an infection within the last two months and one that more likely occurred even earlier. Such details are important for filling in gaps in our understanding COVID-19 infections and tracking their spread in our communities.

Still, there are rare reports of individuals who survived one bout with COVID-19 and were infected with a different SARS-CoV-2 strain a few weeks later [3]. The infrequency of such reports, however, suggests that acquired immunity after SARS-CoV-2 infection is generally protective.

There remain many open questions, and answering them will require conducting larger studies with greater diversity of COVID-19 survivors. So, I’m pleased to note that the NIH’s National Cancer Institute (NCI) recently launched the NCI Serological Sciences Network for COVID19 (SeroNet), now the nation’s largest coordinated effort to characterize the immune response to COVID-19 [4].

The network was established using funds from an emergency Congressional appropriation of more than $300 million to develop, validate, improve, and implement antibody testing for COVID-19 and related technologies. With help from this network and ongoing research around the world, a clearer picture will emerge of acquired immunity that will help to control future outbreaks of COVID-19.


[1] Persistence and decay of human antibody responses to the receptor binding domain of SARS-CoV-2 spike protein in COVID-19 patients. Iyer AS, Jones FK, Nodoushani A, Ryan ET, Harris JB, Charles RC, et al. Sci Immunol. 2020 Oct 8;5(52):eabe0367.

[2] Persistence of serum and saliva antibody responses to SARS-CoV-2 spike antigens in COVID-19 patients. Isho B, Abe KT, Zuo M, Durocher Y, McGeer AJ, Gommerman JL, Gingras AC, et al. Sci Immunol. 2020 Oct 8;5(52):eabe5511.

[3] What reinfections mean for COVID-19. Iwasaki A. Lancet Infect Dis, 2020 October 12. [Epub ahead of print]

[4] NIH to launch the Serological Sciences Network for COVID-19, announce grant and contract awardees. National Institutes of Health. 2020 October 8.


Coronavirus (COVID-19) (NIH)

Charles Lab (Massachusetts General Hospital, Boston)

Gingras Lab (University of Toronto, Canada)

Jennifer Gommerman (University of Toronto, Canada)

NCI Serological Sciences Network for COVID-19 (SeroNet) (National Cancer Institute/NIH)

NIH Support: National Institute of Allergy and Infectious Diseases; National Institute of General Medical Sciences; National Cancer Institute


  • Randolph W. says:

    Tested positive for coved 19 July 15, Tested negative August 18, I have donated plasma 5 times since. All antibodies tested positive as of January 6. My question is: Do I reduce my resistance to covid 19 by donating plasma?

    • Mrs. C says:

      No, sir, the cells that produce antibodies are returned to your bloodstream during the process of plasmapheresis, where they will continue to do their job of making antibodies. I donated plasma only a couple of times after recovering from COVID myself and the process was explained to me in detail. You are protected and, in my humble opinion, you won’t get sick with it again, Welcome to the herd!

  • Debbie says:

    I suffered from Covid in Mar/ Apr last year and was very ill but recovered. I have done two antibody tests one in Oct 20 and one in Dec 20 both tests still show I have the antibodies. Is this a good thing and is it unusual to have these so long after the infection?

  • Sigrid E. says:

    I contracted covid19 in mid June of 2020 without any known symptoms other than a racing heart at night and panic attacks. That condition persisted for about 6 weeks with no cough no fever and without the knowledge of the infection. In mid July, I was tested for covid and quarantined for 20 days following my doctor’s order.
    I was going about my life for 4 weeks without knowing of my infection and always wondered if the quarantine order was too late ore useless.
    In any case, I had a very bad case also due to my COPD, but managed to stay out of the hospital. Not getting much help from my doctor and so much confusing information from the CDC, I just followed my own common sense. Hydration, rest with intermittent exercise to keep the lungs working, 800 mg of Ibuprofin to fight inflammation 400 mg am and 400 mg pm. by 2 , Vit C, Zink.
    In mid August I still tested positive, although in late Aug. beginning of September, I felt I was getting better, getting out of bed, preparing a meal and going for quick shopping trips.
    I started lap swimming every day and thought I had beaten it.

    Sometime in October/ November, I started experiencing strange symptoms: a foggy brain and tremendous fatigue attacking also my legs. These symptoms appeared quite frequently during the day with deadening feelings throughout my head and my entire body. I had also gaps in my memory trying to think where this and that was in my home. I went to see a neurologist and the tests he prescribed came back normal. My lung function test checked out perfect.

    Later I visited my cardiologist because I have some existing problems in my vascular system. Venous reflux and some plaque in the legs’ arteries, that was previously not considered troublesome and to be treated with exercise. These new ultrasounds of heart, venes and arteries, however, showed now severe stenosis in my right leg and some in the left. Heart muscle strong.

    I sought out a holistic approach for all my symptoms and had acupuncture, once a week for 5 months.I did improve my health tremendously and am still sticking with the Acu, certain vitamins, esp. Vit B6, Qi Gong, especially for correct breathing exercises.

    About 3 weeks ago, I was tested for antibodies and had indeed
    the good kind (igG) which is supposedly the one, that keeps one a bit longer immune.
    I will, in another two or three months,

    At this point in my ordeal, I am basically waiting to get normal again, but have read that some patients may never be able to rid themselves of this what the CDC called “post viral symptoms.”

    With this detailed info of my course of the Corona virus infection, I am hoping to help some of you to learn how different everybody is and what to do. Nobody even in the medical field really knows much more than what maybe after 3 months of immunity.

    I do wish that hydroxychloroquine would not have got such bad report, because ( a common drug for certain immune disorders) it would have helped, as is now reported , many of us to recover more quickly and possibly fully and may have prevented so many deaths.

  • T Williams says:

    My family and I all had covid at the end of April last year. We have all tested positive for antibodies this past week (2/10/21). YES!!

  • Ralph H. says:

    After discovering I had cover-19 I was hospitalized for two weeks. I spent 12 days in the ICU and the doctors paid close attention to my oxygen intake. Its been 5 weeks since I was discharged with no apparent symptoms. I had covid-19, pneumonia, and a blood clot. Doctors told my wife after two days I had a better chance of dying than living. I lost 10 pounds but regained that and some since coming home. My wife also contracted the disease but had less problems than me. We are wondering if we should get shots.

  • Rosa R. says:

    I have covid19 positive on march last year i have antibody and still positive for covid19

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