What about re-infections with the COVID virus? Is it common? And will we have cellular immunity?

What about re-infections with the COVID virus Is it common Cellular T-cell immunity

Written by Paul E. Alexander, PhD; Howard Tenenbaum, DDS, PhD; and Parvez Dara, MBA, MD.

We have looked at the published evidence and can conclude based on the existing body of evidence, that reinfections are very rare, if at all, and based on typically one or two instances with questionable confirmation of an actual case of re-infection e.g. flawed PCR testing etc. (references 1, 234567891011, 12131415161718, 19202122, 23).

Importantly, the World Health Organization (WHO) has recently (May 10th 2021 Scientific brief, WHO/2019-nCoV/Sci_Brief/Natural_immunity/2021.1) alluded to what has been clear for many months, which is that people are very rarely re-infected. The WHO is very late but, hey, better late than never. The key points they have stated in this briefing that stand out and warrant a mention (again, we always knew this and tried informing the CDC and WHO of this over the last year) include the following:

i) Within 4 weeks following infection, 90-99% of individuals infected with the SARS-CoV-2 virus develop detectable neutralizing antibodies.

ii) Available scientific data suggests that in most people immune responses remain robust and protective against reinfection for at least 6-8 months after infection (the longest follow up with strong scientific evidence is currently approximately 8 months).

iii) Studies aimed to detect immunological memory including the assessment of cellular immunity by testing for the presence of memory B cells, and CD4+ and CD8+ T cells, observed robust immunity at 6 months post-infection in 95% of subjects under study, which included individuals with asymptomatic, mild, moderate and severe infections.

iv) Current evidence points to most individuals developing strong protective immune responses following natural infection with SARS-CoV-2.

We also wish to re-iterate the accumulated strong evidence that prior infection with other coronaviruses and common cold coronaviruses confer cellular immunity via T-cell immunity etc. (WeiskopfGrifoniLe Bert, Mateus, Tavukcuoglu, CassanitiDykemaEcheverríaBonifacius) (references 123456789). Indeed, the evidence now abounds that SARS-CoV-2-reactive CD4+ T cells as an example, are seen in unexposed individuals, suggesting preexisting cross-reactive T cell memory. “A positive response was observed up to 12 months after COVID-19 infection (median 246 days after symptom onset; range 118-362 days)… long-term SARS-CoV-2 T-cell response might accompany a waning humoral response”. Of note, SARS-CoV-2 T-cell response seems to be mainly mediated by CD4 T cells. This immunity appears also to be long-lasting e.g. SARS-1 has remained for 18 years. Of 23 patients who had SARS-1 in 2003, researchers found all 23 retained memory T cells induced by the parental SARS-1 pathogen in their systems after 17 to 18 years. Moreover, when they looked at convalescent SARS-CoV-2 patients (n=36), they uncovered that the 36 had also produced similar memory T cells.

In closing, we also argue that if you are re-infected, it is most likely not with the initial parental strain you were infected with and most likely with a variant. Moreover, had you developed natural exposure immunity, this is usually a robust and durable safeguard against variants. There are many questions at this time as to the ability of the very narrow ‘spike-specific’ immunity (spike epitopes) conferred by the mRNA and adenovirus vector delivery platforms. It is possible and highly probable that variants could blow past the existing vaccines, and we are seeing this today whereby doctors report that 60% of the new COVID infections already have had both vaccination shots. This phenomenon post-vaccination warrants urgent focus by authorities and study.

Paul Alexander holds a masters of science degree in epidemiology and community health from the University of Toronto, a masters of science degree in evidence-based medicine from Oxford University, masters schooling in Health Sciences also at York University, Toronto, and a PhD in evidence-based medicine and research methods from McMasters University, Hamilton. He currently holds a post as Assistant Professor at McMaster’s University in the HEI Research Methods department and completed his doctoral research and post-doctoral work under the founder of Evidence-based medicine (EBM), Dr. Gordon Guyatt. He served in the Trump Administration as a senior COVID-19 advisor for the Assistant Secretary of Health and Human Services and also worked for WHO and the Pan-American Health Organization in Washington, D.C. from February 2020 onwards as a COVID-19 consultant for research methods and related matters. He also worked for the WHO/PAHO prior to the onset of the pandemic in developing evidence-based tools for low- and middle-income nations. 

Note that views expressed in this opinion article are the writer’s and not necessarily those of TrialSite, Inc.  


  1. And again we come back to the flawed PCR test, still being used at an excessive number of cycles, with the Ct still not being returned with the test results, and still with the blurring of distinction between “cases” and “positive tests”. Garbage in, garbage out, and don’t bet the farm on a really wobbly “test”.

    I am very glad to see in print that natural immunity can be achieved from having other similar illnesses. T cells aren’t as hyperfocused as the super specific antibodies generated or delivered by these vaccines. During this entire pandemic, I think I saw one news story from the UK talking about the amount of natural immunity, which was somewhere between 25% and up, with lots of “ifs” and “maybes” in the story. TPTB have denied, downplayed, and ignored this, keeping the panic going. SSDD.

    Nor is it any surprise to me that natural immunity from having one flavor of this virus works against other flavors, or that natural immunity from having some other similar virus in the past works against getting this virus in any of its flavors. No kidding. Duh. But thank you very much for being forthright enough to actually say that in print. Not that any of the hypnotized zombie sheeple will believe or listen, and almost none of them will find this article or mention of it, nor will the MSM touch this with a 10 foot pole. So you’re preaching to the choir, but it’s a message we like to hear. Well done.

  2. Tom-E, Citoyen – I think that 60% may be referring to the people in the UK catching one of the variants. I read that story in the UK Daily Mail a few weeks back, and at other news sites. This was when the “breakthrough cases” term was first seen in the media.

    1. Thanks Andrew. I didn’t see that. 60% still seems quite high in spite of the differences in the prevalent vaccine.

  3. “we are seeing this today whereby doctors report that 60% of the new COVID infections already have had both vaccination shots. This phenomenon post-vaccination warrants urgent focus by authorities and study” yet there is no citation. Quite an omission for a guy with an evidence based medicine degree.

  4. Of more and greater concern to me is the quite innocuously inserted caveat. As if viruses stick around trying to breach an already tested-and-no-longer-breachable vaccine defence.
    So, the caveat?
    Mutations, Variants and Strains, very specific evolutionary virus adaptations and survival mechanisms. Which is why Ivermectin probably holds the secret to our best chance of dealing with opportunistic viruses SARS-Cov2,3,4… or am I missing something?
    As opposed to fit-for-purpose vaccines, the safety and efficacies which will be the subject of debates for years to come.
    Very insightful article, though. Makes one think, does it not?

  5. Can you site a link for fully vaccinated people being the 60% of covid cases? As far as I know we’ve only had a total of 7,000 people get covid (breakthrough infections) that we’re fully vaccinated in the United States. These people were injected with either of the MRNA vaccines. The AstraZeneca vaccines have a lot more breakthrough infections, but they’re close to 75% effective. The sports team where some of the personnel had breakthrough infections that had minimal or no symptoms did not reveal how many team personnel were employed and vaccinated so in that case I couldn’t calculate a percentage of breakthrough infections. I hope that information becomes public so that they can study other groups more closely with the periodic testing. Then the % of previously undetected breakthrough infections that are occurring after vaccination can be calculated. So far these post vaccination asymptomatic infections have low viral counts so they haven’t spread like it would from an unvaccinated person. That’s very reassuring because as far as I know the vaccines did not confer mucosal immunity in test animals so that was the big worry during development that you could spread it that way but fortunately in human populations it works better than the lab experiments on non humans.

  6. Immune systems are so amazing and impressive when they work as you have reported.
    Have you researched the documentation of infections of COVID-19 that have been reported in the immediate post-vaccination period? What are their immune systems doing? Is there reduced T-cell response or are the T-cells pushed aside – since the vaccine design (mRNA) is to trigger SPECIFIC antibodies that go after the spike proteins [that vaccinated people’s own bodies allegedly put together, just to turn around and attack these proteins with specific neutralizing antibodies?]