How long is antibody duration in Covid 19 ? / Antibodies

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Re: How long is antibody duration in Covid 19 ? / Antibodies

Post by trader32176 »

SARS-CoV-2 immunity can sustain for at least eight months, study finds

11/26/20 ... finds.aspx

How long does immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) last after initial infection? This is one of the important and difficult questions scientists are grappling with today. Fully understanding this central issue has an enormous bearing on the future of public health, the course of the pandemic as well as the efficacy and longevity of future vaccines.

Lasting immunity to SARS-CoV-2, the agent that causes the coronavirus disease 2019 (COVID-19), is questioned because serum antibodies decline during convalescence. However, functional immunity is mediated by long-lived memory T and B cells.

A new study by researchers at Monash University, Australia, has revealed that people who have been infected with COVID-19 showed sustained protection against reinfection for at least eight months.

The study, which was published on the open-source medRxiv* preprint server, shows robust evidence for the likelihood that vaccines will work for long periods.

Although some of the antibodies seem to wane with time, the body retained the ability to remember the virus and generate the response needed to prevent serious illness. Experts believe that this type of immunological memory could last for years.

The study

There has been a steep rise in the number of COVID-19 cases, with many countries experiencing second waves of infections as many businesses and schools have reopened amid the easement of lockdown restrictions worldwide.

To date, over 60.49 million people have been infected, and more than 1.42 million have died.

Some studies have shown that after being infected with COVID-19, there is a decline in antibody response within three months.

In the current study, the researchers aimed to determine the longevity of SARS-CoV-2-specific memory B cells in COVID-19 patients.

To arrive at the study’s findings, the researchers characterized the SARS-CoV-2-specific memory B cell compartment using unique sets of the receptor-binding domain (RBD) and nucleoprotein (NCP) antigens.

The team recruited 25 COVID-19 patients and collected 36 blood samples from day four after infection up to day 242. They measured the systemic memory B cell response to SARS-CoV-2 infection.

The team emphasized that from vaccination studies in mice and humans, local systemic memory B cells are phenotypically different. It was also shown that influenza-specific memory B cells persist in the lungs of mice and play an essential role in protection from reinfection.

“As knowledge of SARS-CoV-2 and human lung immunology evolve, we will gain insight into what is required for a protective response to this respiratory virus. However, we propose that the establishment of systemic immunity will prevent severe systemic COVID-19, and reinfection may be limited to a mild or asymptomatic upper respiratory tract infection,” the researchers explained in the study.

Memory B cells

Circulating RBD- and NCP-specific memory B cells were detected early after infection and persisted over 242 days after the symptoms appeared.

Further, it appeared that early after being exposed, the Ag-specific cells expressed immunoglobulin M (IgM) over time, followed by the predominance of immunoglobulin G (IgG) antibodies.

The antibodies against the virus started to drop after 20 days post-infection. However, all patients continued to retain memory B cells that recognize one of two components of SARS-CoV-2, the spike and nucleocapsid proteins. These virus-specific memory B cells were detected up to eight months after infection.

Studying the SARS-CoV-2-specific memory B cells could potentially be used as a backup marker of humoral immunity in vaccination studies. At present, COVID-19 vaccine trials explore SARS-CoV-2 specific and neutralizing antibodies as markers of vaccine efficacy.

The results of the current study gives a glimpse of hope that candidate vaccines may provide long-lasting protection against SARS-CoV-2. As antibody levels drop when the immune response contracts, IgG memory B cells remain present, showing that SARS-CoV-2 infection triggers long-term humoral immunity.

The authors said that the study results give hope to the efficacy of vaccines against the virus.

“These results are important because they show, definitively, that patients infected with the COVID-19 virus do retain immunity against the virus and the disease,” Menno van Zelm, associate professor at Monash University, said.

“This has been a black cloud hanging over the potential protection that could be provided by any COVID-19 vaccine and gives real hope that, once a vaccine or vaccines are developed, they will provide long-term protection,” he added.
*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.


COVID-19 Dashboard by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University (JHU) - ... 7b48e9ecf6

Journal reference:

Hartley, G., Edwards, E., Aui, P., van Zelm, M., et al. (2020). Rapid and lasting generation of B-cell memory to SARS-CoV-2 spike and nucleocapsid proteins in COVID-19 disease and convalescence. medRxiv. doi:, ... 20233544v1
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Joined: Fri Jun 26, 2020 5:22 am

Re: How long is antibody duration in Covid 19 ? / Antibodies

Post by trader32176 »

Study shows antibody responses persisting 10 months after SARS-CoV-2 infection

2/24/21 ... ction.aspx

Researchers in Italy have conducted a study showing that patients who had tested positive for infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) still had neutralizing antibodies against the virus 10 months later.

SARS-CoV-2 is the agent responsible for the coronavirus disease 2019 (COVID-19) pandemic that continues to pose a global public health threat and has now claimed the lives of more than 2.49 million people.

The researchers evaluated antibody responses over the course of 10 months among 30 people who were diagnosed with SARS-CoV-2 infection in the Umbria region of Italy between the 1st and 30th March 2020.

At ten months post-infection, 19 (63%) of the individuals still had detectable levels of neutralizing immunoglobulin G (IgG) antibodies against SARS-CoV-2.

Furthermore, no cases of reinfection occurred among any of the participants, despite a surge in daily infections with mutant strains occurring in the Umbria region during the study period.

A pre-print version of the research paper is available on the medRxiv* server, while the article undergoes peer review.

Concerns surrounding antibody responses to SARS-CoV-2

Since the COVID-19 outbreak began in Wuhan, China, in late December 2019, studies have shown that humoral (antibody) responses among recovered patients can last anywhere from three months to more than eight months.

The SARS-CoV-2 virus expresses four key structural proteins, among which the spike (S) protein and nucleocapsid (N) protein are the most immunogenic.

The spike protein is the main structure the virus uses to bind to and gain entry to host cells.

As the initial stage of the infection process, the spike binds to the host cell receptor angiotensin-converting enzyme 2 (ACE-2) via its receptor-binding domain (RBD).

The spike RBD is the main target of SARS-CoV-2 neutralizing antibodies, which can be detected as soon as six days following confirmation of infection by polymerase chain reaction (PCR).

Studies published in 2020 have raised concerns regarding the duration of immunity provided by these neutralizing antibodies, warning that “rapidly waning immunity” could lead to false-negative immunoassay results.

“Improved understanding of immunity offered by the antibodies developed against SARS-CoV-2 is critical,” writes Puya Dehgani-Mobaraki from Associazione Naso Sano in Umbria, Italy and colleagues.

What did the researchers do?

The researchers conducted a longitudinal observational analysis of 114 patients in the Umbria region who had tested positive for SARS-CoV-2 by real-time quantitative PCR between the 1st and 30th March.

They conducted sequential serological tests over a ten-month period among 30 of the participants who attended all of the follow-up visits.

Blood samples were collected at six different time (T) points, with the first sample taken two months post-infection in the month of May (T0). Further samples were then taken one month (T1), three months (T2), five months (T3), six months (T4) and eight months (T5) after T0.

The presence and persistence of SARS-CoV-2-specific antibodies were assessed using two commercial chemiluminescence immunoassays (CLIA), with the CLIA positivity cut-off set at >1.01.

The participants were divided into those with mild disease (n=17) and those with a moderate-to-severe disease (n=13).

What did the study find?

The team reports that anti-spike-RBD IgG was detected in 19 (63.3%) of the 30 participants at T5 – ten months after infection was initially confirmed.

Among both the mild disease group and the moderate-to-severe disease group the trend of SAR-CoV-2-specifc IgM titers stayed below the CLIA positivity cut-off (>1.01) and significantly decreased over the ten-month period.

By contrast, the IgG titer trend stayed above the CLIA positivity cut-off in both groups and no significant changes in titer were observed.

Furthermore, “our study reported zero cases of reinfection despite the fact that the Umbria region currently is experiencing a surge in daily cases with mutant strains,” concludes the team.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:

Dehgani-Mobaraki P, et al. Neutralizing antibody responses 10 months after mild and moderately-severe SARS-CoV-2 infection. medRxiv, 2021. doi:, ... 21252225v1
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Re: How long is antibody duration in Covid 19 ? / Antibodies

Post by trader32176 »

COVID-19 antibodies can protect against reinfection for at least eight months

3/23/21 ... onths.aspx

Seroconversion occurs in up to 99% of people following infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen that is responsible for the ongoing coronavirus disease 2019 (COVID-19) pandemic. The question, however, is how long these antibodies persist and how far they protect against reinfection. A new study released on the medRxiv* preprint server offers hope that recovered patients are largely immune to reinfection for at least eight months.

The absence of testing in the early stages of the pandemic, as well as the high incidence of asymptomatic infection, led to estimated seropositivity rates of less than 10%. Reinfection, meanwhile, has been reported in a rarity of cases and has mostly resulted in mild symptoms, indicating a high degree of protective immunity following recovery from COVID-19.

Study details

The current study takes advantage of the two waves of COVID-19 that occurred in Switzerland, the first peaking in March and the second in November, 2020. The city of Geneva had a high incidence of confirmed SARS-CoV-2 infections, at about 8,600/100,000 people.

The researchers looked at the risk of reinfections in a situation with high community transmission. The two groups they compared either had or did not have detectable antibodies to SARS-CoV-2. The aim was to estimate the infection rate in either group.

The study matched each individual in the seropositive group to two seronegative controls. The sociodemographic characteristics of each group were comparable. So were the body mass index, and type and number of comorbidities in each group.

The follow-up continued for 36 and 25 weeks in the seropositive and seronegative groups, respectively. The testing rate was slightly higher among the seronegatives, at 1.52 per person vs. 1.39 in the seropositives.

However, the positive test fraction was lower in the seropositive group, at 2.4% vs. 11% in the seronegative group.

What were the results?

Only seven of 448 seropositive individuals had a positive polymerase chain reaction test for the virus. Five were likely to be reinfections, the other two probably not.

Conversely, 16% of seronegative individuals were positive, which indicates an incidence of 5 per 1,000 person-weeks. Over the entire follow-up period, the chances of being infected were 94% less for seropositive individuals compared to the other group.

What are the implications?

The study provides strong evidence that the presence of antibodies to SARS-CoV-2 is associated with strong protection against reinfection, as indicated by a positive test, at eight or more months following the first positive test.

Earlier reports have also shown that among over 1,200 seropositive healthcare workers in the UK, only two infections were detected after six months of follow-up. Both were asymptomatic. This yields an incidence rate ratio of 0.12.

The sample in the above study was composed of healthy participants of working age, and the period of the study was one of low incidence, with only 1 positive test per 10,000 days at risk. In contrast, the current study was carried out over a period with six-fold higher incidence.

A Qatar study, including over 1,30,000 confirmed infections, showed that reinfection was detected in only 0.05% of them. In this case, reinfection was determined on the basis of a positive PCR test at 45 or more days from the first positive swab.

This was, however, a study in a country that had only one wave of COVID-19, and where young workers were chiefly affected during the early phase, which was characterized by the rapid, extensive spread. Here, the infections dropped steeply following August 2020.

Strengths of this study

The current study covers a more representative sample, including many elderly individuals. Moreover, the follow-up period extended into the second wave, several months after seroconversion, with a high incidence of infection.

Thus, this supports the hypothesis that SARS-CoV-2 infection is followed by robust and durable antibody-mediated protection against reinfection. The degree of protection matches, at least, the preliminary results reported following vaccination with lipid nanoparticle-mRNA-based vaccines, at 90%.

Some degree of underestimation of actual reinfection is inevitable, perhaps, given that reinfections are milder in clinical presentation, and also because seropositive patients are aware that they have already had and recovered from the infection.

This is likely to be low, because testing was extensively carried out in the second wave, more so than in the first, with the ratio of undetected cases to detected ones falling from about 12 to 3, respectively. Secondly, both seropositive and seronegative subjects had similar testing rates, but a drastically lower positive test rate in the former.


Documented SARS-CoV-2 reinfections were exceedingly rare, with an incidence of 0.3 infections for every 1000 persons-week, and none were severe.”

The risk of reinfection is apparently reduced ten-fold by seroconversion after SARS-CoV-2 infection, as recorded at eight or more months after initial infection. These findings will help shape vaccination policies to provide maximum coverage while allowing appropriate relaxations of non-pharmaceutical interventions as soon as possible.

The extent of protection against variants of concern such as the UK variant cannot be estimated from this study, since these were present in very low numbers at that time. Further research may explore the correlation, if any, between antibody titers and the risk of reinfection, and the percentage of persistent seropositivity with prolonged monitoring.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:

Leidi, A. et al. (2021). Risk of reinfection after seroconversion to SARS-CoV-2: A population-based propensity-score matched cohort study. medRxiv preprint. doi:, ... 21253889v1
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