Today I’ll answer some “reader mailbag” questions about COVID-19 vaccine booster doses, breakthrough infections, Delta, and how they all connect.
Should the U.S. be offering COVID-19 vaccine booster doses?
I ended the last post by talking about how booster doses were not going to have a significant impact on the large case counts or crowded hospitals, because those are largely problems of the unvaccinated. You have probably read news articles with various experts criticizing the U.S. decision to recommend booster doses for just this reason.
If the choice here in the U.S. was between offering booster doses or having a population vaccination rate of 80% across all 50 states, the choice would be easy — we take the 80% vaccination rate. But supply is not the primary issue behind our suboptimal vaccination rates. As a matter of fact, I don’t think there even is a “primary issue” because there are so many factors playing into our low vaccination rates. Regardless, recommending booster doses is unlikely to have a meaningful effect on our vaccination rates. Therefore, if booster doses will help people achieve maximal protection for the maximum amount of time (which I think they will), then it makes good sense to roll them out.
Is there any relationship between a person’s adverse reactions to the mRNA vaccines (Moderna and Pfizer) and whether or not the vaccines “worked”?
Nope. We now have good evidence comparing people with adverse reactions (e.g. fatigue, headache, etc.) vs. people without. There is no correlation between either the presence or the magnitude of adverse reactions and the effectiveness of the vaccines.
What about checking for antibodies in vaccinated patients?
It would be great if there was an easy, reliable, and rapid way to determine if we are protected from COVID. Unfortunately, there isn’t. Antibody tests vary from one lab to another and are often not quantitative, meaning they won’t tell you your concentration of antibodies. Not to mention we have no easy way to measure cellular immunity. There are simply too many variables and too many tests of varying quality to routinely recommend them for patients following vaccination. With the exception of a person with a compromised immune system, it is safe to assume that the vaccine is working appropriately.
I know too many people with breakthrough infections. It doesn’t seem like the vaccines are that effective.
Please read this post for some explanation behind how to assess COVID-19 vaccine effectiveness. Before we dive into evidence, remember, we are not talking absolutes. I’m not going to promise you won’t experience a COVID-19 infection. As Mary Poppins would say, that is a pie crust promise — easily made, easily broken. My point is to provide some context to the noise, and hopefully calm some of your fears. Again, take a look at the linked post in this paragraph for more detailed information.
How common are breakthrough infections?
There are a couple ways I can break this down, but in general breakthrough infections are not terribly common. Here’s the data I use to come to this conclusion.
States that report breakthrough infections consistently show very low rates, usually less than 1%. That means that less than 1% of those known to be immunized report a breakthrough infection. The “true” number may not be that low because many states don’t report that kind of data, including those states with the lowest immunization rates.
There have been reports measuring breakthrough infection rates in smaller, closed environments, usually healthcare institutions or prisons. Those data sets show up to about a 3% rate of breakthrough infections.
Granted, many of those reports were from time periods early after vaccination. So perhaps the rates of breakthrough infections will increase as people’s circulating antibodies decline. But the 3% mentioned above is probably a reasonable estimate for many populations.
That does NOT mean your chance of a breakthrough infection is 3%. Your individual risk is based on the vaccination rate of your community, the number of people you are in close contact with, and a host of other variables (e.g. mask wearing). Instead, this means that 3% of vaccinated patients experience a breakthrough infection. Three percent is not rare, but it certainly is not common.
But all I hear about in my circle of friends is breakthrough infections. What about that?
Most of the people who have shared concerns with me describe their social circles as nearly entirely vaccinated. Therefore, the only kind of infections that could be seen are breakthrough infections.
Try this math experiment. How many people do you personally know who have had a breakthrough infection? Divide that number by 0.03. (It’s that 3% I mentioned above.) Take the result of that division. If you know at least that many people, then the rate of breakthrough infections in your “world” fits well into the available data.
For example, let’s assume you personally know six people with breakthrough infections. So six divided by 0.03 gives you 200 people. Do you know at least 200 people?
Wait I was told there wouldn’t be math. Please stop.
Sorry. I can’t stop.
We currently have 170 million people fully vaccinated in the U.S. Let’s assume that 3% is the “true” rate of breakthrough infections. That means that we should realistically expect about 5.1 million breakthrough infections. Three percent is a small percentage, but 5.1 million is a large number.
And, of course, you will only hear about the breakthrough infections. How many news reports are there about people who had confirmed exposures to COVID-19 but who never developed infection? Nowhere near as many as there are about breakthrough infections.
As I’ve said numerous times in this blog — you will only hear about the numerator; you will never hear about the denominator. So the human brain, which is already conditioned to respond emotionally and quickly to danger, is conditioned even more so to focus on the 3%, not on the 97%.
Are the breakthrough infections related to the Delta variant?
It’s abundantly clear that essentially every infection in the U.S. is due to the Delta variant. So in that way, yes, we could say that the breakthrough infections are because of the Delta variant. The question we should ask — which is a counterfactual that can’t be fully answered— is would we see the same breakthrough infections if we were still dealing with alpha, beta, gamma, blah blah blah variant. The reality is that breakthrough infections are inevitable in the real world where a perfect vaccine is impossible.
Are we getting booster doses because of the Delta variant?
No, we would be talking about waning antibodies and the value of booster doses regardless of what variant was running around. Antibodies don’t wane over time because of the variant that is circulating. They wane because our immune systems need to be “taught” to keep producing antibodies.
But I keep hearing the vaccine is less effective against the Delta variant?
I’ll refer you to this post and this post for more details, but I’ll also add a bit more information here. If the concentration of antibodies declines over time such that there are less people with protective concentrations of antibodies now than before, and if there is a new variant circulating at the same time as this decline in antibodies, then you can’t say that the vaccine is less effective or ineffective against the variant. The decline in effectiveness is just as likely, if not more likely, due to the passing of time as it is the current variant.
The best interpretation of the totality of the available evidence is that the vaccines (especially the mRNA vaccines) produce antibodies that protect against infection and severe disease, even with the Delta variant. Such protection would be expected to be reduced, but not entirely eliminated, with the passage of time, which is what boosters will help with. Again, all of this would be the case regardless of which Greek letter variant is circulating.
Stay safe, and go make some lemonade.
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The Infectious Pharmacist 