It is one of the big questions during the COVID-19 pandemic. How long do antibodies against SARS-CoV-2, the novel coronavirus that causes the disease, last? And if they are gone, is your immune system still able to offer protection against getting infected again?

    New research published in The New England Journal of Medicine suggests that the antibodies developed after a mild infection decay and disappear within a few months. However, they may still offer protection.

    “Infection with this coronavirus does not necessarily generate lifetime immunity,” said Buddy Creech, an infectious disease specialist at Vanderbilt University who was not involved in the study. But he told AP, antibodies are not the whole story. The immune system does remember how to make new antibodies when needed and other parts of the immune system are in play as well.

    The research was published by investigators at the David Geffen School of Medicine at University of California, Los Angeles and published as a letter. In their research, they confirmed infection in 30 out of 34 participants using a PCR assay. The four others had symptoms consistent with COVID-19 and lived with people who were known to have the disease but were not tested due to mild illness and limited testing availability. Most had mild disease, with two receiving low-flow supplemental oxygen and CytoDyn’s leronlimab, a CCR5 antagonist. They did not receive Gilead Sciences’ remdesivir. The mean age was 43 years, there were 20 women and 14 men.

    Of the 34 participants, 31 had two serial measurements of IgG levels, with the three others having three serial measurements. The first evaluation was taken at a mean of 37 days after onset of symptoms, ranging from 18 to 65 days. The final measurements were taken at a mean of 86 days after the onset of symptoms ranging from 44 to 119 days.

    The antibodies, they found, had a half-life of 73 days. That means that half of the antibodies would be gone at 73 days. This was consistent with research out of China.

    The authors, led by Otto Yang, wrote that the data “call for caution regarding antibody-based ‘immunity passports,’ herd immunity, and perhaps vaccine durability.”

    Creech agrees, but notes that other parts of the immune system are involved. B cells manufacture antibodies, but they also develop a memory of how to do it again. “They would get called into action very quickly when there’s a new exposure to the virus,” Creech told AP. “It’s as if they lie dormant, just waiting.”

    T cells, another type of immune cell, are also primed to attack the virus if it returns. This is increasingly becoming an important metric in evaluating the effectiveness of potential vaccines against COVID-19.

    Alison Criss, an immunologist at the University of Virginia, told AP, that even though circulating antibodies may not last long, what is key to find out is if and how people recreate antibodies if they’re exposed to the COVID-19 virus again and if they protect against another infection. “We also need to know if there is a protective T cell response.”

    The authors noted in their letter, “The protective role of antibodies against SARS-CoV-2 is unknown, but these antibodies are usually a reasonable correlate of antiviral immunity, and anti-receptor-binding domain antibody levels correspond to plasma viral neutralizing activity. Given that early antibody decay after acute viral antigenic exposure is approximately exponential, we found antibody loss that was quicker than that reported for SARS-CoV-1, and our findings were more consistent with those of Long et al.”

    They refer to a study currently online ahead of print in Nature Medicine that evaluated 37 asymptomatic individuals in the Wanzhou District of China with confirmed COVID-19 infections, but no relevant clinical symptoms in the previous 14 days and during hospitalization.

    In the Wanzhou study, they found that the virus-specific IgG levels in this group were significantly lower compared to those analyzed in the symptomatic group in the acute phase of the disease. And as the patients recovered, the asymptomatic patients’ IgG levels and neutralizing antibody levels decreased more quickly than in symptomatic patients. “Forty percent of the asymptomatic individuals became seronegative and 12.9% of the symptomatic group became negative for IgG in the early convalescent phase,” the Long et al. group wrote.

    The California group concludes, “Our findings raise concern that humoral immunity against SARS-COV-2 may not be long lasting in persons with mild illness, who compose the majority of persons with COVID-19. It is difficult to extrapolate beyond our observation period of approximately 90 days because it is likely that the decay will decelerate…. Further studies will be needed to define a quantitative protection threshold and rate of decline of antiviral antibodies beyond 90 days.”

    How long do COVID-19 antibodies last?
    At this time, it is unknown for how long antibodies persist following infection and if the presence of antibodies confers protective immunity. more
    Can Omicron cause long Covid?
    Among omicron cases, 2501 (4·5%) of 56 003 people experienced long COVID and, among delta cases, 4469 (10·8%) of 41 361 people experienced long COVID. Omicron cases were less likely to experience long COVID for all vaccine timings, with an odds ratio ranging from 0·24 (0·20–0·32) to 0·50 (0·43–0·59). more
    How long do you have antibodies after contracting Covid?
    After infection with the COVID-19 virus, it can take two to three weeks to develop enough antibodies to be detected in an antibody test, so it's important that you're not tested too soon. Antibodies may be detected in your blood for several months or more after you recover from COVID-19 . more
    How long does it take for antibodies to show up after Covid?
    It typically takes 1 to 3 weeks after infection or vaccination for your body to make antibodies. If you are infected, you may get sick and spread the virus before you develop antibodies. more
    Who is getting long Covid?
    People who have experienced more severe COVID-19 illness, especially those who were hospitalized or needed intensive care. People who had underlying health conditions prior to COVID-19. more
    How long do Covid IgM antibodies last?
    There are different types of antibodies. This test is for IgM and IgG antibodies. Typically the IgM antibody develops soon after infection (3 to 10 days), but does not last long. The IgG is often detectable later, after day 9, and can last much longer, months to years. more
    How long do antibodies last in people who have mild COVID-19 cases?
    A UCLA study shows that in people with mild cases of COVID-19, antibodies against SARS-CoV-2 — the virus that causes the disease — drop sharply over the first three months after infection, decreasing by roughly half every 36 days. If sustained at that rate, the antibodies would disappear within about a year. more
    How long could COVID-19 immunity last after you had COVID-19?
    So while it is becoming clear that some form of immune response against the virus can be detected for more than a year after COVID-19 infection, their levels may not be enough to provide full protection against reinfection. more
    What are Post-COVID conditions or Long COVID?
    Post-COVID conditions (PCC, or Long COVID) are a wide range of new, returning, or ongoing health problems people can experience four or more weeks after first being infected with the virus that causes COVID-19. more
    How long can you test positive for COVID-19 after having COVID-19?
    According to the Centers for Disease Control and Prevention, some people who contract COVID-19 can have detectable virus for up to three months, but that doesn't mean they are contagious. When it comes to testing, the PCR tests are more likely to continue picking up the virus following infection. more
    How long do antibodies stay in your blood after Covid?
    After infection with the COVID-19 virus, it can take two to three weeks to develop enough antibodies to be detected in an antibody test, so it's important that you're not tested too soon. Antibodies may be detected in your blood for several months or more after you recover from COVID-19 . more


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