Over on the CDC website, an amazing resource, there’s this statement about the COVID-19 vaccines:
The best COVID-19 vaccine is the first one that is available to you. Do not wait for a specific brand.
I certainly agreed with that comment back in late 2020 and early 2021, when demand for vaccines exceeded supply, and we faced record daily case numbers and a race against more transmissible variants, in particular B.1.1.7.
But fast-forward to today, and things COVID-19-wise in the United States have remarkably, wonderfully, changed. (Knocks wood.) Vaccine supply is plentiful. More than half the population has received at least one shot. Cases, hospitalizations, and deaths continue to decline.
Plus, we’ve got a much-expanded database on vaccine effectiveness and safety, in particular with the mRNA vaccines made by Pfizer and Moderna, and an emerging sense of the J&J vaccine as well. Is the CDC’s statement still true?
Let’s take a look at the three vaccines available to us right now, comparing them in various metrics.
Effectiveness. We were appropriately cautious about making cross-study comparisons between results of the Pfizer and Moderna phase 3 studies versus those from the J&J study — different seasons, different variants, different geographic locations, different protocols.
But let’s be blunt — a difference between 95% and 60–70% efficacy in preventing symptomatic disease is pretty large. Plus, now we have many population-based studies of the mRNA vaccines showing 90% or higher effectiveness in clinical practice. Effectiveness studies for the J&J vaccine are just starting to appear, and the data look quite similar to the results from the clinical trial — in other words, around 70% effective.
Safety. Data on the rare — but serious — syndrome of thrombosis with thrombocytopenia (TTS) linked to the J&J vaccine were updated at the latest ACIP meeting on May 12. There have now been 28 cases after nearly 9 million shots. The median age was 40 (range 18–59), with 22 women and 6 men, with the highest risk among women ages 30–39 (roughly 1 case for every 80,000 doses). Again, amazing work by our vaccine safety program in identifying this important safety signal.
The mRNA vaccines, meanwhile, have no confirmed cases of TTS among over 245 million doses administered. Those are extremely reassuring data. Yes, subjective side effects are more common with the mRNA vaccines than with the J&J vaccine, and CDC now is tracking reports of myocarditis among younger people receiving these vaccines — connection still not confirmed — but many of these myocarditis cases have been mild. Meanwhile, some of the TTS cases have led to permanent disability and even death.
Boosters. It’s the question everyone wants to know — when will we need booster shots? From they are inevitable since antibody titers decline to never since cellular immunity is forever, the honest response is that we just don’t know.
But, if antibody titers are a marker for when we’ll need boosters, this modeling study shows a correlation between antibody titers and protection, implying we’ll need them sooner after the J&J vaccine than the mRNA vaccines. Which would not be very surprising with a one-shot approach, would it?
Convenience. Here the J&J vaccine should be the clear winner, requiring only one shot, and also being easy to ship and store. When we first heard of this advantage, many of us assumed this would mean a far greater supply and availability of the J&J vaccine. However, this is currently not the case, at least not yet. Manufacturing of the mRNA vaccines has clearly accelerated, and they are widely available in many diverse locations.
These differences are stark enough that I posted this poll last week:
It seems that most agree with me that the mRNA vaccines are now preferred. If you have a treatment or vaccine that’s both more effective and safer, you don’t need to be a disease modeler to figure out which one is better.
In the comments to this poll, some cited the contrast between where we are currently in the United States, and the situation globally — which remains dire, and still warrants a “first vaccine available” strategy. I cannot stress this point enough.
Others mentioned the importance of patient choice. I acknowledge this is an important consideration for individual cases — someone might need to reach that magic 2-week protected threshold sooner, or not have the time to come back for a second dose. These reasons could be enough to justify going forward with the J&J vaccine preferentially.
However, if someone asked me what COVID-19 vaccine I’d recommend, based on what we know now, my answer would not be “whichever one you prefer” or “whichever one you are offered first” — especially if it were a 35-year-old woman.
It would be an mRNA vaccine.
Safiyya S. Shabazz, MD
