Marc Veldhoen Profile picture
Head of Lab, Professor Basic Immunology, T cell expert. MSc 🇳🇱, PhD 🇬🇧 Post-only account from December 1st.
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Nov 10 9 tweets 4 min read
RFK Jr. lacks a medical or life sciences background, and it shows in his persistent obsessions.

As scientists, we understand that wanting a hypothesis to be true doesn’t make it so.

Vaccines do not cause or contribute to autism.

1/9 Image There is extensive data and decades of studies, repeatedly reviewed, and the link between vaccines and autism has been definitively disproven.


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Nov 8 7 tweets 2 min read
When people are repeatedly told something is harmful or wrong, even if the evidence says otherwise, many eventually start to believe it.

The argument here is that if it's not vaccines or WiFi, then something must be making us all unhealthy. But are we actually less healthy?
1/7 Image Some of us are less healthy—just look at rising rates of overweight and obesity, which bring many secondary health issues. But the cause isn’t vaccines, WiFi, or 5G. It’s largely due to diet and lack of exercise. And no, there are no quick fixes for this.
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Nov 7 10 tweets 3 min read
This clip and public pronouncements are used to claim that RFK jr. does not want to ban vaccines. But that largely misses the danger of what is being portrayed here.

It is the sinister sowing of doubts with disinformation that is the issue.

Part 2.
1/10 Image In part 1 I discussed the incorrect statements, based on misunderstanding how vaccines work, what they are, that they are preventative, that there is no precise time, that all have been tested in clinical trials, and that they should be given to healthy children. Why them?

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Nov 7 10 tweets 4 min read
This clip and public pronouncements are used to claim that RFK jr. does not want to ban vaccines. But that largely misses the danger of what is being portrayed here.

It is the sinister "art" of sowing doubt with disinformation and tropes that is the issue.

Part 1.
1/10 Image He claims it needs to be based on "good science." No vaccine offered is not based on good science. They are all based on detailed knowledge of how our immune system and its cells work, and they were all tested in pre-clinical models, clinical trials, and post-authorisation.
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Nov 6 10 tweets 2 min read
It’s easy to assign blame—on U.S. voters for electing a leader who may not serve the best interests of Americans or humanity (climate, trade tarifs). But this trend isn’t unique; we’re seeing similar shifts globally, including in Europe.
1/10 Image Though it may feel bleak, policy is still to be made, and we can influence it. Today brings frustration, even grief, but tomorrow is another chance. Don’t let anger win; instead, let’s support those who need protection and focus on constructive action.

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Nov 5 10 tweets 3 min read
Utilizing blood single-cell transcriptomics to integrate intrinsic and systemic immune aging

Another one on ageing cells from the blood, already abused bc many do not understand what it means.


1/10biorxiv.org/content/10.110… Single-cell RNA sequencing (scRNA-seq) is a powerful technique, allowing in-depth analysis of single cells instead of bulk populations. But, as always, it is as good as the material you work with. You need to know your starting material to understand the limitations.
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Nov 5 5 tweets 2 min read
Mixing "chronic" with "repeated".

Chronic inflammation, such as seen around tumours can give a phenotype of exhausted T cells. Importantly, this is not permanent but can be overcome with antibodies (e.g. anti-PD-1).

Why is this not the same as repeated stimulation?
1/5 Image During acute inflammation, many molecules are upregulated at the surface of cells. These include many of the same markers, such as CTLA-4 and PD-1. That in itself does not signal "exhaustion".

Effector T cells die. There is no need for them, and they cause a potential danger
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Oct 31 10 tweets 2 min read
Infectious agents have three strategies to maintain themselves:
1) Wait for neutralising antibodies to wane and re-infect. This means the pathogen has to be quick (infect, multiply, and transmit). Established memory B and T cells will be established and respond fast.
1/10 Image 2) Together with 1), mutating to enhance infection changes. These include most respiratory viruses. They are generating variants selected on the basis of reduced neutralising antibody binding.

3) Relying largely on hosts without immunity. This does not mean no infection.
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Oct 27 5 tweets 2 min read
National- and state-level SARS-CoV-2 immunity trends from January 2020 to December 2023: a mathematical modeling analysis

Estimated population-level immunity to SARS-CoV-2 for each of the fifty United States.


1/5medrxiv.org/content/10.110… On December 30, 2023, 99.9% of the U.S. population had experienced immunological exposure to SARS-CoV-2 through infection and/or vaccination, with 99.4% (95% credible interval (CrI): 92.4-100%) having had at least one SARS-CoV-2 infection.
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Oct 26 7 tweets 2 min read
Cycles of Susceptibility: Immunity Debt Explains Altered Infectious Disease Dynamics Post-Pandemic

The absence of infection can, for some pathogens, cause and bounce back and increase the risk of disease: the Immunity gap.


1/7academic.oup.com/cid/advance-ar… The immunity gap is when immunity of the population and individuals relies on boosting from infection. This is the norm with most infections.

Measures trying to prevent the spread of pathogens are general and reduce in infection of many.
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Oct 26 10 tweets 4 min read
Antigen specificity.

It is a difficult concept to grasp. Some have studied it for 5 years, spent 10,000 hours on it, and written a book about it, but it is too hard to understand.
1/10 Image An antigen is anything the immune system can recognise. However, I will limit this to proteins, small pieces of which are called peptides, the specific amino acid sequence recognised by an antibody or T cell is an epitope.

A complex process makes an antibody.
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Oct 24 5 tweets 2 min read
Repeated COVID-19 mRNA-based vaccination contributes to SARS-CoV-2 neutralizing antibody responses in the mucosa

2 papers, showing mRNA vaccines provide IgA levels in the nasal cavity to neutralise SARS-CoV-2, derived from circulating antibodies.


1/5science.org/doi/10.1126/sc… SARS-CoV-2 XBB.1.5 mRNA booster vaccination elicits limited mucosal immunity

This is still not the same as infection, providing extra resident memory T cells and local IgA-producing B cells.


2/5science.org/doi/10.1126/sc…
Oct 20 6 tweets 2 min read
How to show you are science illiterate.

To understand a study, you actually have to read it. You need to understand what the authors actually did and report. If you do not do that or report it like this, you are not a scientist but a scaremongerer. Image These wrong assertions are based on this study


Look at the methods section before anything else. What did the authors study?

Children aged 6-17, that part is correct. Who were they, representative of all 6-17 year olds?jamanetwork.com/journals/jama/…
Oct 17 10 tweets 3 min read
Prevalent and persistent new-onset autoantibodies in mild to severe COVID-19

Upon an immune response, antibodies reactive with self can be detected, SARS-CoV-2 is again no exception.


1/10nature.com/articles/s4146… Infections are known to trigger flares of autoimmune diseases in humans. Infection-mediated autoimmune bystander (non-specific) and antigen-specific mechanisms can contribute to autoimmunity. Several publications have shown this is the same for SC2.


2/10sciencedirect.com/science/articl…
Oct 13 9 tweets 2 min read
Predicting pathogen mutual invasibility and co-circulation

When a new variant is better in competition with the variants present at that time, what happens with the other variants?


1/9science.org/doi/10.1126/sc… This is not a simple question. For some viruses, there are multiple strains, e.g parainfluenza virus, influenza A and B strains, and HSV. Yet, SARS-CoV-2 has only variants. At least part of the answer is immunological niches: the space to divert enough to become a strain.
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Oct 12 10 tweets 4 min read
Multi-ancestry GWAS of Long COVID identifies immune-related loci and etiological links to chronic fatigue syndrome, fibromyalgia and depression

Are there genetic predispositions for risk of #LongCovid? There are, and include three main loci.


1/10medrxiv.org/content/10.110… The pre-print makes use of genotyped data from 23andMe adult research participants: European (42,899 cases, 94,721 controls), Latinx (8,631 cases, 20,351 controls), and African-American (2,234 cases, 5,596 controls) genetic ancestry groups.
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Oct 9 10 tweets 5 min read
There are some posts discussing Influenza vs SARS-CoV-2. Is one worse?

The data is what matters. However, it is not easy to get the data, judge its accuracy and understand it. Important: let the data speak. Let's have a few take-home messages about what we observe.
1/10 Image Someone much better at crunching these numbers, @MichaelSFuhrer, made this graph, based on science and reasonable assumptions.

This is the US:
x.com/MichaelSFuhrer…

This is Australia:
x.com/MichaelSFuhrer…
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Oct 8 10 tweets 3 min read
There is this piece of nonsense going around claiming it is impossible to vaccinate, undoing over 200 years of practical evidence and a140 years of increasing detailed cellular and molecular insights.

Of course, this is false. Vaccines imitate an infection.
1/10 Image It concerns the work of Charles Richet, who was not a nice man. In 1913, he won a Nobel prize for his work on severe allergic reactions (a type-2 immune response), before we understood much of immunology. He did not receive it for finding out how to poison people!
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Oct 4 10 tweets 3 min read
There are a flurry of posts on SC2 and neurodegenerative (and other) diseases. This causes, understandably so, anxiety and fear among some. This is largely due to headlines and bad messages. It is critical to understand some context; SC2 is not unique or particularly bad.
1/10 Image Any infection (trauma) can, and often should, cause an inflammatory response. Some of the cells and soluble mediators act locally, but others systemically. This allows many organs to work together to combat the invader. e.g. your liver will get signals to increase body temp.
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Oct 3 10 tweets 3 min read
Pas op voor de waanzin die de Bruut post. Zoals bijna altijd zit het weer flink fout. Om met het laatste te beginnen: onderzoekers houden altijd de deur open voor meer informatie en schrijven standaard dat meer onderzoek nodig is. We gaan er nooit vanuit alles te weten.
1/10 Image Het gaat om deze publicatie. Lees om de titel heen. It dit een negatief? Nee, helemaal niet.

Repeated COVID-19 mRNA vaccination results in IgG4 class switching and decreased NK cell activation by S1-specific antibodies in older adults


2/10immunityageing.biomedcentral.com/articles/10.11…
Sep 30 10 tweets 3 min read
The post-pandemic hospital and mortality burden of COVID-19 compared with influenza: A national cohort study in Denmark, May 2022 to June 2024

COVID-19 was worse than the flu in the first 2 post-pandemic years 2022-2024.


1/10medrxiv.org/content/10.110… A cohort study including residents in Denmark from May 16, 2022, to June 7, 2024, obtained from national registries. Data from PCR+ admissions from COVID-19 and flu. Important; this is limited to those needing medical assistance.
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