Don’t Use Antibody Tests Post Vaccine to Determine Immunity Robert Gorter, MD, PhD

08-06-21 12:21:00,

Don’t Use Antibody Tests Post Vaccine to Determine Immunity

by

Robert Gorter, MD, PhD.et al.

June 3rd, 2021

The U.S. Food and Drug Administration (FDA) issued a safety communication in May 2021, warning both the public and health care providers not to use SARS-CoV-2 antibody tests to gauge immunity, especially after the COVID-19 vaccination.

There’s a significant difference in the immune response triggered by natural infection and vaccination

In the case of COVID-19 mRNA vaccines, such as those produced by Pfizer and Moderna, antibodies to the spike protein are induced; in the case of natural SARS-CoV-2 infection, nucleocapsid proteins are detected by antibody testing

Because of this, people who have received a COVID-19 vaccine and haven’t previously been infected will receive a negative antibody test, provided the test doesn’t detect the vaccine-induced spike protein antibodies

A positive result from a SARS-CoV-2 antibody test could indicate the previous infection or could also be caused by the vaccine

Antibodies are proteins your body makes in response to infections and will be detectable in your blood after infection as a sign of your body’s battle against that pathogen. Antibodies for COVID-19 are believed to develop within one to three weeks after infection, and a positive antibody test for COVID-19 means that a person may have been infected with SARS-CoV-2, the virus that causes COVID-19, in the past.

Titer blood tests, which measure the presence and amounts of certain antibodies in your blood, are sometimes used to prove immunity to a disease. If your titer is positive, which means it’s above a set value, you’re considered to be immune to the disease, such as measles, mumps, or rubella.

This is why, for instance, proof of prior diagnosis with chickenpox, measles, and mumps is allowed instead of vaccination to enter most U.S. public schools — once you’ve had the disease and recovered, you are immune life-long.

In the case of COVID-19, however, the U.S. Food and Drug Administration issued a safety communication in May 2021, (5) warning both the public and health care providers not to use SARS-CoV-2 antibody tests to gauge immunity,

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New Antibody Seroprevalence Data

27-10-20 08:21:00,

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A new section on antibody seroprevalence data per country has been added to our covid IFR studies overview page.

By early summer, global hotspots like New York City and Bergamo reached antibody seroprevalence values of about 25%. Some densely populated regions in India and Brazil reached antibody values of up to 50%. Places like London, Madrid and Stockholm reached about 15%.

However, even in hard hit countries like the US, the UK, Spain, France and Italy, the national antibody seroprevalence reached only about 5% on average. In much of Eastern Europe as well as in Germany and Canada, antibody values remained well below 2% until early summer.

On the other hand, some places reached higher values than previously assumed. For example, according to a highly sensitive antibody test assay, Chicago reached 20% instead of just 5%.

In addition, two new charts showing the mortality in the US since 1900 and in Sweden since 1851 have been added to the section on overall mortality. The Swedish mortality is comparable to previous strong seasonal flu waves; the US mortality is comparable to the medium influenza pandemics of 1957 and 1968, but remains far below the 1918 and 1929 flu pandemics.

As previously noted, the median age of covid deaths is above 80 in most of Western Europe, about 78 in the US (due to higher rates of metabolic disease) and about 70 years in Brazil.

Regarding post-acute or long covid, the latest British study shows that most people fully recover within 12 days, about 15% have symptoms for at least four weeks, about 5% have symptoms for at least eight weeks, and about 2% have symptoms for at least 12 weeks. These values appear to be comparable to earlier medium flu pandemics. (More on long covid)

View: Antibody seroprevalence per country (overview)

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