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By Miriam Raftery


May 3, 2021 (Milpitas, Calif.) – If you’ve had COVID and have not yet been vaccinated, here’s an important fact to consider. A new study published in BioMed Central (BMC) found that fewer than half of COVID positive patients retained their disease fighting antibodies more than 100 days after infection. This revelation comes as health experts assess how long natural immunity against the coronavirus disease lasts.

Natural immunity occurs through exposure to the actual disease organism, and not from a vaccine. Natural immunity can be long-lasting but varies widely, with a half-life from 11 years for tetanus to over 200 years for measles and mumps. COVID, in contrast, behaves more like the seasonal flu, with natural immunity lasting less than a year.


According to the study, only 44% of patients who had mild-to-moderate COVID still had antibodies beyond day 100. 


“The fact that 56% of subjects lose virus neutralizing antibodies after only a few months could explain the timing of successive waves of the disease,” said Dr. Jyotsna Shah, PhD and lead author of the study. “We saw a big surge in cases in the fall of last year, and additional hot spots have popped up in 2021.”


To perform the study, scientists from IGeneX Laboratory looked at patient samples obtained at different times after they’d received a positive covid test result. These samples were tested over a long period to see how long antibodies remained present.


COVID-19 vaccines, by contrast, provide immunity that lasts longer than immunity after having the virus.


Additional studies are underway to monitor long-term immune response from the vaccine. 

A recent study of fully vaccinated people found that antibodies persisted for at least six months after the second dose was administered, which is roughly twice as long as natural immunity. Vaccines have also been shown to protect against rapidly spreading variants.

To access the study, pvisit the BMC Infectious Diseases website.

IGeneX, which conducted the study, provides industry leading COVID-19 RT-PCR, antibody, and T cell tests for major hospitals, cities, employers, professional sports teams and airline travelers. The company has tested more than 5000 domestic and international travelers for the coronavirus.

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Low Antibodies Not Whole Story

The study referenced measured antibodies in the blood. However, there are memory B-cells which produce antibodies. Actually B-cells are the ones that take on average about 10 days to both recognize an invader and produce enough antibodies to combat it. However, usually a small number of the specific antibodies course through our blood and lymph systems so that if the same invader returns they can act immediately and the memory B-cells can also start pumping out immediately more of the specific antibodies, so that often we don’t even know there has been a second invasion. After an infection has been dealt with not good to have the specific antibodies in large numbers because during height of battle they can take up as much as 20% of blood.

However, there are two arms to the adaptive immune system. The second is T-cells that also play a role in defeating an invader. And according to Field’s Virology, a two-volume Bible of virology, the corona S-spike protein elicits both B and T cell responses. There are a number of recent peer-reviewed articles in medical journals that have found active and memory T-cells following COVID-19 infections. And T-cells usually have some cross-immunity. Quite simply, though perfectly matched for invader, also able to recognize range of variants.

Yep, the Moderna and Pfizer mRNA COVID vaccines do lead to much higher levels of antibodies than the actual infection and studies have found last at least six months and probably much longer; but the important thing is memory B- and T-cells. If antibodies too low, then in most cases one could experience a mild discomfort; but the two memory cells will be churning out antibodies and T-cells at high levels and super fast.