If anyone claims vaccines haven’t been properly studied, show them this:

We’ve now logged 500 randomized, controlled vaccine trials into our dataset with ~7.2M participants. The vast majority of trials reported safety outcomes. Many more trials to come.
bit.ly/4le8z7D Huge thanks to the inspiration and co-leader of the project, @BradSpellberg, and to our amazing team of volunteers who have been putting many hours into this - @AliSMV7, @alejodiaz81, @DhandAbhay, @ThePharmFox, @zacroBID, @TravisBNielsen, Dr. Matthew Phillips, @SarahRawi1, @IDwithNWD, Dr. Kusha Davar, Dr. Devin Clark, and countless anonymous contributors.

1/ Tucker Carlson: “Do you think overall the COVID vaccine killed more people than it saved?”
RFK Jr: “The truth is, I don’t know.”

This is outrageous.
I do know.
The answer is: unequivocally no. 🧵 2/ RFK Jr then added:

“And the reason I don't know is because the studies that were done by my agency were sub-standard, and they were not designed to answer that question."

I cared for hundreds of COVID patients and watched far too many die - including young, relatively healthy adults who never had a chance to get vaccinated, or who declined it.

And I’ve reviewed the evidence. Many of the studies he’s dismissing are anything but “sub-standard.”

It’s not even close.

This claim about the Amish deserves correction with actual data. 🧵

https://twitter.com/rwmalonemd/status/1939373583823995361

2/ Research shows that many Amish families do vaccinate their children. Studies find that anywhere from 41% to 85% of Amish parents have vaccinated at least some of their children, depending on the community and time period.

RFK Jr's thimerosal thread is a masterclass in misinformation. Let's fact-check it line by line. 🧵 2/ CLAIM: “There are high bolus doses of mercury in flu shots.”

FACT: 96% of flu vaccines are thimerosal-free.
Multi-dose vials contain 25 mcg per dose. That’s not a “high bolus.”
fda.gov/vaccines-blood…

It’s not easy to navigate the maelstrom of misinformation. Grateful to @megtirrell and @boulware_dr for cutting through it.

Slides prepared for ACIP this week by former CHD leader Lyn Redwood cited a 2008 Neurotoxicology study on thimerosal and “long-term brain harm.”

But the study doesn’t exist. The listed author says he never wrote it and his actual research found no such effect.

Debates should be grounded in evidence, not phantom citations.

Thimerosal has been thoroughly studied for decades. Here's what the evidence actually shows🧵👇
cnn.com/2025/06/24/hea… 2/ What the evidence actually says

Thimerosal has been used in vaccines and biologics since the 1930s. It’s highly effective at killing bacteria and preventing contamination, especially in opened multi-dose vials.

Thimerosal contains ethylmercury, not methylmercury. Ethylmercury is broken down and excreted quickly; unlike methylmercury, it doesn’t build up or persist in the body.

In 1999, U.S. health agencies recommended removing thimerosal from childhood vaccines as a precaution, not because of evidence of harm. By 2003, all thimerosal-containing pediatric vaccines (except some flu shots) had expired. pubmed.ncbi.nlm.nih.gov/10418806/

It’s understandable to have questions about aluminum in vaccines. Here are the key facts:
🧵 1⃣ Why is aluminum there?

A tiny amount of aluminum salt acts as an adjuvant - a helper that tells your immune system, “Pay attention!” This lets the vaccine work better with less antigen (the piece of virus or bacteria that trains immunity). In this sense, it's dose-sparing: less antigen per shot.

RFK Jr. went on national TV and spouted egregious, dangerous falsehoods about vaccines. As a parent and infectious diseases doctor, I couldn't stay silent. @FoxNews might not fact-check him, but I will. I've reviewed the trials. I've catalogued them. I have receipts. 🧵

https://twitter.com/atrupar/status/1933254404519469135

❌CLAIM 1: "97% of people on [ACIP] had conflicts of interest"

✅REALITY: Only 41% received any industry payments, mostly under $55k over 6 years
This is flatly false. Reuters reviewed all 17 voting members of the outgoing ACIP panel:
6 received $80 or less TOTAL over 6 years

7 received between $4k-$55k total over 6 years (mostly travel, meals, occasional consulting)
4 had no reported industry payments at all
That's 7/17 = 41%. Not 97%.

CDC rules require recusal for any vote tied to a relevant conflict. Meeting minutes show ONE recusal in the reviewed period.
ACIP members are unpaid volunteer experts. They don't get royalties, don't keep pharma stock, don't get flown to golf courses.
A published review found <5% of ACIP votes over the past decade involved a declared conflict.
reuters.com/business/healt…

I’ve been getting a lot of questions about what it really means for a vaccine trial to be “placebo-controlled” - and how that differs from other control groups.

It’s a great question, and clarity here really matters.

Let’s break it down. 🧵

CC @EricTopol @angie_rasmussen @PeterHotez @trvrb 3 control types:

1. Placebo (saline/inert)

2. Active comparator (e.g., alum-only or licensed vax)

3. No-intervention (observed only)

2/

“White lung syndrome” is a made-up term. Any pneumonia appears as a white opacity on an x-ray or CT, which is partly how the diagnosis of pneumonia is made. But it’s not specific to pneumonia, and it’s certainly not specific to Mycoplasma pneumoniae, which is not “mysterious”. 🧵 Mycoplasma pneumoniae is a bacterium, not a virus. (It’s one of the smallest free-living organisms.) It can cause pneumonia in kids age 5-17 and can be severe but is very uncommonly fatal. Radiographic findings vary but can look worse than anticipated from the physical signs. 2/3

Urinalyses (UAs) are widely used, yet are often ordered inappropriately, and the results are not as meaningful as one might think.

Pyuria (WBCs in urine) is nonspecific (although the absence of pyuria should call into question a diagnosis of UTI).
🧵
1/5 Leukocyte esterase is a screening test for pyuria (see above).

Hematuria can occur in patients with UTIs, but is also not specific, and generally doesn’t change management. (If there are clinical signs of obstructive pyelo in a patient with sepsis, check a noncontrast CT.)

2/5

I disagree with this statement:

“…protection against severe disease may only last about four to six months.”

I think that the vast majority of people can expect protection against severe COVID-19 to last much longer than 6 months. 🧵
1/

npr.org/sections/healt… As I’ve previously mentioned, accurately determining the duration of vaccine-induced immune protection is challenging, for many reasons:

1. Many who were vaccinated earlier were at highest risk, which could confound results.

2/

Antibodies continue to get all the attention.

This @washingtonpost piece gives them too much credit, and leaves out the critical role of cellular immunity.

1/

washingtonpost.com/health/2023/01… The main reason why most people need not worry about severe illness caused by XBB.1.5 or any other Omicron subvariant is because non-neutralizing antibodies, memory B cells, & CD4+/CD8+ T cells provide longlasting protection against all variants to date.

onlinelibrary.wiley.com/doi/10.1111/im…

The Argentinian outbreak of pneumonia was found to be due to Legionnaire’s disease (caused by Legionella bacteria)

This was first recognized as the cause of the outbreak at the American Legion convention in Philadelphia in 1976, which affected 221 people and led to 34 deaths

https://twitter.com/Tuliodna/status/1566084754511912962

The American Legion outbreak went unsolved for months. Ultimately attributed to airborne spread of a bacterium. Exposure was environmental (not person-to-person) and may have occurred in the hotel lobby.

Legionella grow in warm water, cooling towers, plumbing, fountains, etc. 2/

This thread has gotten a lot of attention, but I think there are a few points worth highlighting:

1st: I’m glad Dr. Wachter’s son has recovered

2nd: I’m not surprised, because #VaccinesWork 🧵

https://twitter.com/bob_wachter/status/1479913165039095810

3rd: he states that his 28-yo 3x-vaxxed son is “moderately high-risk” because he’s “overweight.”

If he were *unvaccinated*, yes, being obese (especially if his BMI were ≥30, based on data from meta-analyses) increases the risk for severe outcomes.

bit.ly/3rnDFPM

2/

What’s driving the rapid spread of Omicron?

In this Danish study @LyngseF & colleagues found no significant difference between household secondary attack rates of Omicron (29%) vs Delta (28%) among *unvaccinated* individuals (OR 1.17, 0.99-1.38).
1/
bit.ly/3ESwfbY But the secondary attack rate of Omicron vs Delta was 2.6x higher among fully vaccinated & 3.7x higher among booster-vaccinated individuals.

More evidence that immune evasion is likely driving the rapid spread of Omicron rather than an inherent increase in transmissibility.
2/

I still don’t think people understand how well the vaccines *really* work. So let me try to explain.

I spend most of my time treating patients admitted to the hospital with various infections. My colleagues & I are called to see nearly every hospitalized covid patient.🧵 Last time this year, before vaccines were available, I cared for dozens of covid patients a week. Many of them were older, often from nursing homes, and many of them died. My colleagues & I lost over a hundred patients last year. 2/

How well does vaccine-induced immunity hold up against Omicron?

TL;DR it’s still too soon to know

(it took months to get enough real-world VE data for Delta, FWIW) 🧵 I hear estimates of vaccine effectiveness being quoted as if they’re definitive, but they’re based on small numbers or predictions from modeling, which can’t be relied upon for precision, especially when it comes to determining VE vs severe disease. 2/
bbc.in/3q7o5XH

“Covid-19 vaccine breakthrough infections in Veterans Health Administration” (pre-print)

Retrospective cohort study of ~3 million fully vaccinated people (median age 70) from 1/1/21-8/31/21

Post-vax infection in only 0.37%

Hospitalization in 0.07%

1/5
medrxiv.org/content/10.110… Younger age was associated w/ more post-vax events, attributed to differences in behavior. (aHR 0.65; 95% CI 0.63-0.66; p<0.001)

Differences by type of vaccine: more events in J&J recipients > Pfizer > Moderna

(50% had received Moderna, 43% Pfizer, 7% J&J)

2/5

🧵When I look at the bottom right of this figure from @PHE_uk, I can’t help but wonder why so many people are calling *right now* for Pfizer boosters for people >60 w/o comorbidities.

Effectiveness against hospitalization sustained >=95% x >5 months.
1/
bit.ly/3lvGdZa And then there’s this huge Kaiser matched cohort study. 350k vaxxed matched to 350k unvaxxed.

Median age 65

Moderna vaccine effectiveness against hospitalization out to 5 months (thru June): 95.8%

2/
bit.ly/3Es0qaG

My 2-year-old loves swings. His favorite playground finally opened, but all the swings have been removed.
SF reopened indoor dining before playgrounds.
And indoor dining is limited to 2 hours, while playing at a playground is limited to 30 minutes. bit.ly/2IEDWeg 🧵 When considering the differential in risk of transmission, this is backwards.
As a parent of 2 toddlers who went through their snotty-nosed years, I get it. Kids in general-and playgrounds in particular-are often associated w/ germs. But #SARSCoV2 is different. (2)

As an ID doc who regularly sees #COVID19 patients & is responsible for starting & discontinuing isolation, a few comments:

I understand why there’s distrust but Trump may actually no longer be infectious at this point.

Thread

https://twitter.com/jdiamond1/status/1315093470940282880

(The fact that he wasn’t properly isolating before this evening is a different story.)

(2/n)