Monday, April 26, 2021

Resuming use of the J&J COVID-19 vaccine is the right call

After a 10-day pause to review safety concerns about the Johnson & Johnson (Janssen) COVID-19 vaccine, the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention (CDC) announced late on Friday that they had accepted the recommendation of the Advisory Committee on Immunization Practices to resume the vaccine's use with a new warning about the extremely rare risk of thrombosis-thrombocytopenia syndrome (TTS).

From a public health perspective, this decision was unsurprising. Although sufficient supplies of two other COVID-19 vaccines are available to vaccinate every adult in the U.S., these mRNA vaccines require two doses (delaying their protective effects by 3-4 weeks compared to the single dose J&J vaccine) and have storage and handling requirements that are challenging for primary care practices. As I argued in a previous post, reaching patients who are hesitant to be vaccinated will require a relationship with a trusted clinician that doesn't exist at a mass vaccination site or a chain pharmacy. During the J&J vaccine pause, 10 million doses were sitting in refrigerators rather than going into arms. Based on a modeling study (slides 38-48), the CDC estimated that resuming J&J vaccination could achieve the goal of vaccinating every American adult who desired a COVID-19 vaccine 14 days earlier than not resuming, as well as preventing 1,435 deaths and 2,236 intensive care unit admissions over a 6-month period with 26 additional episodes of TTS.

When I'm counseling a patient in my office, though, public health benefits usually aren't the main motivating factor in the decision to be vaccinated. So let's drill down to the risks and benefits of J&J vaccination for women ages 18-49. For this group, the risk of TTS from J&J vaccine is 7 in 1,000,000, or about 1 in 143,000 persons. Using this risk estimator from The Economist, the risk of death from COVID-19 in 40 to 50 year old women without other risk factors (e.g., asthma) ranges from 1 in 250 to 1 in 1000. Let's say 1 in 500 for all unvaccinated persons in this age group for simplicity's sake. Of course not all of them will contract COVID-19, but it's reasonable to assume, based on serology surveys and the lifting of social distancing and mask mandates across the country, that at least 1 in 4 of them is likely to be infected by the end of this year. That means their risk of dying from COVID-19 in 2021 is 1 in 2000.

What about younger women? Per the CDC website, 30-39 year olds are about 3 times less likely to die from COVID than 40-49 year olds, while 18-29 year olds are about 10 times less likely.

Let's assume that J&J vaccination reduces COVID-19 deaths by at least 75% (my best guess based on the Phase 3 trial results, which didn't accrue enough deaths to precisely calculate mortality benefits, but was 76%-90% effective against severe/critical disease). So, for women younger than 30, their risk of COVID death in 2021 is about 1 in 20,000. This would fall to 1 in 80,000 after vaccination, preventing 1 in 26,667 deaths, compared to a risk of TTS of 1 in 143,000. For women age 30-39, risk of COVID death is about 1 in 6000 (1 in 24,000 after vaccination, preventing 1 in 8000 deaths), compared to a risk of TTS of 1 in 143,000. For women age 40-49, risk of COVID death is 1 in 2000 (1 in 8000 after vaccination, preventing 1 in 2667 deaths) compared to a risk of TTS of 1 in 143,000.

Another way to look at these numbers: for each case of TTS that occurs due to J&J vaccine in women age 18-29, 30-39, and 40-49, respectively, the numbers of COVID-19 deaths prevented would be 5, 18, and 54.

In summary, J&J vaccine being better than no vaccine, even for healthy women in their 20s with the lowest potential benefit, doesn't look like a close call. And the risk of death from TTS associated with the vaccine is no more than 20%, and should be lower in the future since doctors now know not to treat it with heparin, which can make it worse. Finally, remember that we are discussing two very rare outcomes: a young woman receiving COVID-19 vaccine most likely won't have her life saved from it or experience TTS. That's where the public health benefits of everyone being vaccinated come back in: by decreasing transmission, vaccination reduces the risk of exposure for other people at substantially higher risk of hospitalization and death, and it accelerates the timetable when we can safely "go back to normal" and fully reap the physical, emotional and economic benefits of widespread immunity to the coronavirus.