Hi, Everyone,

I know I’ve been writing about Covid a lot lately. And I know that not all of you signed up for that.

But this information is time-sensitive—and important. We’re at a historic moment. Individuals, parents, public health officials, and leaders of all types are making choices that will have lasting consequences, and I want to be sure I’ve done my part in making those decisions as informed as possible.

I’ve written a few emails over the past few weeks analyzing the risks and benefits of the Covid vaccines in children and young adults. If you missed them the first time, you can read them here, here, and here

In two of those emails, I reviewed the growing evidence of vaccine-induced myocarditis in young males, particularly between the ages of 16 and 24

I’d like to zoom in on that topic today. Here in the U.S., the mainstream medical establishment is suggesting that everyone—including healthy young males—get booster shots to protect themselves from rising rates of Omicron variant infections.  

But is that really a safe and evidence-based recommendation?

Since the start of the pandemic, I’ve been advocating for a more nuanced approach to vaccination specifically and Covid in general. We don’t need to (and shouldn’t) make the same recommendation regarding vaccination to everyone, regardless of their age, sex, or health status. It is now crystal clear from the data that the risk-benefit calculation varies widely across those demographic groups. 

What’s more, we shouldn’t treat all the Covid vaccines as if they are identical or interchangeable. They are not. For example, as we’ll see below, we now have numerous studies showing that the Moderna vaccine is significantly more likely to cause myocarditis than the Pfizer, Johnson & Johnson, AstraZeneca, and Novavax vaccines. 

So, the vaccine guidance that we might give to a 75-year-old woman who is obese, diabetic, and has a relatively high risk of severe Covid should be entirely different from what we give to an 18-year-old male who is lean, healthy, and at extremely low risk of severe Covid. 

With this in mind, let’s examine the following question. 

What is the risk of myocarditis in young males who receive the Covid vaccines? 

Public health scientists in Ontario, Canada, published an important study on this topic in early December 2021. 

They looked at the incidence of myocarditis/pericarditis among males aged 18 to 24 after receiving two doses of Covid vaccines. 

The results were disturbing—to say the least:

  • Those who received Pfizer for the first dose and then Moderna for the second dose (within 30 days) had a risk of 1 in 1,287
  • Those who received two doses of Moderna within 30 days (the recommended schedule) had a risk of 1 in 2,653
  • Those who received two doses of Pfizer within 30 days (again, the recommended schedule) had a risk of 1 in 10,526

A similar paper published back in September 2021 by Tracy Beth Høeg, a physician with a PhD in public health and epidemiology from UC Davis, examined rates of myocarditis in 12- to 17-year-old boys and found an overall vaccine-associated risk of myocarditis of 1 in 6,173 in 12- to 15-year-olds and 1 in 10,638 in 16- to 17-year-olds. 

Yet Dr. Høeg and her colleagues noted that even this high risk is likely to be an underestimate for at least three reasons:

  • Adverse events are underreported by the Vaccine Adverse Event Reporting System (VAERS) as discussed here.
  • The VAERS reports used in this study “were of children with myocarditis with cardiac symptoms and not cases of incidental cardiac inflammation noted on imaging.” In other words, asymptomatic myocarditis cases were not included.
  • The risk of vaccine-induced myocarditis is four times higher in kids who have been previously infected with SARS-CoV-2. At this point in the pandemic, it is likely that over 50% of kids have already had Covid-19, which means that the myocarditis risk may be increasing.

Isn’t the risk of myocarditis from Covid higher than it is from the vaccines?

This is a common claim that I often hear in the mainstream media or on social media when the question of vaccine-induced myocarditis comes up.

The problem is that it’s simply not true. 

In the September 2021 study, Dr. Høeg’s team found that the risk of myocarditis from the vaccine in 12- to 15-year-old healthy boys was four to six times higher than the risk of myocarditis from Covid-19 infection. The study also found that 86% of boys diagnosed with vaccine-induced myocarditis required hospital care, indicating that these were not mild, transient cases that resolved on their own.

Here is the figure from their paper showing this: 

The only time the risk of hospitalization from Covid-19 was greater than the risk of myocarditis is when kids have one or more pre-existing conditions and when disease prevalence and hospitalization rates are moderate or high. 

How does the risk of hospitalization from Covid-19 compare to the risk of myocarditis in 18- to 24-year-old males? 

We don’t have an exact age range comparison, but we can use data from the Centers for Disease Control and Prevention (CDC) to get close. According to a weekly report called “Rates of COVID-19-Associated Hospitalization,” segmented by age group, we see that as of November 27, 2021, the rate of hospitalization for men and women (this report doesn’t separate by sex) aged 18 to 29 was 3.2 per 100,000 or 1 in 31,250:

 The highest rate of hospitalization at any time during the pandemic in this age group was last year at this time, the week ending December 12, at 6.4 per 100,000, or 1 in 15,625

 This compares to rates of vaccine-induced myocarditis in 18- to 24-year-old males ranging from 1 in 1,287 for Pfizer + Moderna to 1 in 10,526 for two doses of Pfizer, assuming both doses are taken within the recommended 30-day window. 

Two new studies make it even more clear that the risk of myocarditis is higher from the vaccine than from Covid in young males who receive Moderna

The two studies I mentioned above should be enough to warrant caution in vaccinating healthy 12- to 24-year-old males, particularly with the Moderna shot. 

But another paper published in Nature Medicine on December 14, 2021, raised even more cause for concern.

What makes this paper particularly important is that it stratified vaccine-induced myocarditis rates by both age and sex. This is critical because we know that the risk of myocarditis from the vaccines is far higher in young males than in any other demographic group.

What did the researchers find?

Figure 2 in the paper clearly shows that, for both men and women under 40 years old, the risk of myocarditis from two shots of Moderna exceeds the risk of myocarditis from SARS-CoV-2 infection (Moderna is labeled as mRNA-1,273 in the figure, the orange bars second and third from right, and SARS-CoV-2 infection is the red bar on the right):

As disturbing as these data are, they still don’t capture the extent to which the risk of myocarditis from the Moderna shot exceeds the risk of myocarditis from Covid in young males for two reasons:

  1. To study the risk of myocarditis from Covid in people under age 40, the authors only looked at people with a documented, positive SARS-CoV-2 test. This dramatically overestimated the rate of myocarditis in this population because we know that asymptomatic infections are common in young people, and many of them do not get tested. If the authors had used seroprevalence data to establish whether individuals under age 40 had been exposed to SARS-CoV-2, the denominator would have been much bigger, and the red bar in the figure above would have been much shorter. This would make it even more clear that two shots of Moderna carry a higher risk of myocarditis than a SARS-CoV-2 infection—and it may have even made that true for one shot of Moderna. 
  2. The analysis in the figure above lumped men and women together. This obscures the much higher risk for men.

Fortunately, the authors published a pre-print on December 25, 2021, to address issue number 2 above. They stratified the vaccine-induced myocarditis risks by both sex and age, and this is what they found (this figure is from page 13 of the study PDF):

We can draw the following conclusions from this figure for men under 40 years of age:

  1. The Moderna vaccine (represented by the blue bars)—both a single dose and two doses—carries a higher risk of myocarditis than SARS-CoV-2 infection (represented by the red bar on the right).
  2. The second and third doses of Pfizer (represented by the green bars) carry a higher risk of myocarditis than SARS-CoV-2 infection.
  3. The second dose of AstraZeneca (represented by the orange bar on the left) carries a higher risk of myocarditis than SARS-CoV-2 infection. 
  4. Pfizer boosters (dose 3) carry a higher risk of myocarditis than SARS-CoV-2 infection. (This study didn’t have enough data on Moderna boosters to evaluate them.) 

This is already alarming and should lead to an immediate reevaluation of our current vaccine strategy for all individuals under age 40—especially men.

Yet it still doesn’t capture the full risk for younger males. 

Why? Because the authors of this paper, unfortunately, lumped all men under age 40 together. We know from previous research that the risk is highest in males 16 to 24 years old, so if they had separated out that group, the difference in myocarditis rates between the vaccines and SARS-CoV-2 infection would have been even more stark

What’s more, as I mentioned above, they are only comparing the risk of vaccine-induced myocarditis against the risk of myocarditis in people with a positive SARS-CoV-2 test. If they instead did this comparison with people who have antibodies to Covid, it would have been more accurate, and the differences would have been even greater.

We don’t have convincing data that boosters benefit young males

Despite these disturbing data, the U.S. and many other countries are pushing forward with booster campaigns—even for young, healthy individuals (both male and female). 

But do we really know what the potential benefits of boosters are for this demographic? 


In fact, as Dr. Vinay Prasad of UCSF has documented, two senior U.S. Food and Drug Administration (FDA) officials resigned in September 2021, almost certainly in protest of the White House’s decision to promote booster shots without any evidence supporting their use in young, healthy people. 

Those senior FDA scientists went on to publish, along with other scientists, an editorial in the Lancet criticizing the lack of evidence to support boosters.  

Omicron is milder than previous variants and likely evades current vaccines

Another consideration in the risk-benefit analysis for vaccines and boosters in young adults—particularly males—is that infection with Omicron appears to be far milder than with previous variants, and multiple studies from around the world have shown that our current vaccines are not as effective (and/or don’t provide enduring protection) against Omicron. 

I’ve written about this elsewhere, and I’ll be revisiting this topic soon. 


We’ve covered a lot of ground in this email, so let me summarize the key takeaways. 

The most recent and comprehensive research suggests that, when compared with SARS-CoV-2 infection:

  • Two shots of Moderna carry a higher risk of myocarditis for both men and women under 40 years old. 
  • Both a single shot and two shots of Moderna carry a higher risk of myocarditis for men under age 40.
  • Two shots of Pfizer carry a higher risk of myocarditis for men under age 40.
  • Two shots of AstraZeneca carry a higher risk of myocarditis for men under age 40.
  • A Pfizer booster carries a higher risk of myocarditis for men under age 40.
  • A Moderna booster carries a higher risk of myocarditis for men under age 40 (this isn’t confirmed in the data above but is almost certainly true given that both one and two shots of Moderna carry a higher risk).

To be clear, I’m not necessarily saying no young males should ever get the Covid vaccine. That is a decision that should be left to the individual (or their parents, if they’re a minor) and their physician, based on a number of different factors.

My point here is that we need to be honest and open about the risks, and we need a more nuanced approach. If a young person is going to proceed with vaccination, the studies I reviewed above clearly indicate that the particular vaccine chosen and how it is administered (i.e., one shot, two shots, three shots, etc.) makes a huge difference in terms of risk-benefit. 

For example, a single shot of the Johnson & Johnson or AstraZeneca vaccine is likely to carry a far lower risk of myocarditis than three Moderna shots. 

Why aren’t our public health officials in the U.S. acknowledging this? 

Some other industrialized countries have already banned or restricted the Moderna vaccine for young people. Germany and France did this back in November 2021. Five Scandinavian countries, including Finland, Denmark, and Sweden, did it in October 2021, and Iceland halted Moderna for all age groups. 

These countries are making decisions based on the available evidence. 

But here in the U.S., our decisions seem to be based more on tribalism and ego. And the result of this will be thousands of unnecessary and completely preventable cases of myocarditis, some of which will be quite severe and possibly even fatal. 

We’re willing to sacrifice the health and well-being of our young people—males in particular—at the altar of political expediency and “team affiliation.” 

 This is unforgivable. And it will haunt us for decades to come.

In health,