I Got the Johnson & Johnson Vaccine. I'm Not Losing Sleep. 1

Here’s how to think about the federal investigation into rare but severe blood clots associated with the vaccine.

About a week ago, I received the Johnson & Johnson Covid-19 vaccine. It was a joyous moment, after more than a year of fear of the coronavirus. Then, on Tuesday, I had a flurry of texts from concerned family members, friends and colleagues who had recently seen the news. Health authorities had requested a pause for the Johnson & Johnson vaccine to investigate six blood clotting cases among women who had been vaccinated.

The news that a vaccine that has been given to over seven million Americans could cause a rare but serious side effect is understandably concerning. Especially when the one-dose Johnson & Johnson vaccine has been lauded as a way to reach high-risk and underserved communities, such as people who are homebound. The decision to pause the use of this vaccine is also controversial; many public health experts are worried that this will hinder vaccination rates and erode confidence in people who are reluctant or skeptical of vaccines, ultimately preventing people from getting vaccinated and pushing population-level immunity further out of reach.

But I think the pause makes sense. And even though I am a woman and fall within the age group of people who experienced clotting, I am not worried about my own personal risk.

This announcement indicated that the vaccine safety system is working as intended. People who received the Johnson & Johnson vaccine recently, or are planning to in the future, can feel reassured by this process.

The side effects identified, if indeed they are side effects of the vaccine, are rare but serious. What prompted the pause is that six women aged 18 to 48 developed an uncommon blood clotting disorder. This specific condition, called cerebral venous sinus thrombosis, occurs when clots form in a major vein draining blood from the brain, which also can occur with a deficiency in blood platelets. It’s essentially a very specific and unusual type of stroke.

Extremely rare side effects like these are too uncommon to be detected in a phase 3 clinical trial, even if it has enrolled 40,000 participants. This is true for other drugs and vaccines outside of the context of Covid-19, and is one reason the Food and Drug Administration and the Centers for Disease Control and Prevention monitors a vaccine’s safety as it is rolled out to the public. Even if the risk is very low, experts need to figure out how low.

This surveillance is also important for determining how to treat side effects when they do occur. In this case, the C.D.C. advisory committee determined that the blood clots studied should be treated in a specific way because of the platelet deficiencies observed in these cases. Blood clots are often treated with the blood thinner heparin. But since the clotting disorder resembles a rare condition caused by heparin, the experts are advising against using the drug, as it could make people’s conditions worse.

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Questions surrounding the Covid-19 vaccine and its rollout.

By making this determination and distributing information about how the blood clots respond to common treatments quickly, the C.D.C. is giving medical workers the tools they need to treat anyone who might show any signs of these rare side effects from the Johnson & Johnson vaccine.

With so much at stake, it’s crucial to reinforce public confidence in how these vaccines are being regulated. If it is turns out, after further study, that the blood clotting disorder is indeed caused by the vaccine, then it remains an extremely rare occurrence. Even if more cases are discovered, the risk of this happening to you remains vanishingly slim.

If this issue is only seen among younger people, it is unlikely that the Johnson & Johnson vaccine is going to be pulled off the market. Instead, regulators may recommend that this vaccine be given only to groups who are not at risk, just as aspirin, for example, is not recommended for children with viral infections because of the risk of developing Reye’s syndrome, a severe and fatal condition that can result in death or permanent brain damage.

There is a possibility that the vaccine will be only recommended to certain age groups that are less at risk for blood clots, as have been implemented in countries like Canada for the AstraZeneca vaccine, which has been linked to similar blood clotting episodes. To make that kind of informed assessment, advisers and regulators need to have a complete set of data and sufficient time to thoroughly review it.

While we don’t yet know if this condition is even related to vaccination, some back-of-the-envelope math can help us understand the relative risks. Considering how many people received the Johnson & Johnson vaccine, six cases is a one in one million event.

Approximately 1.5 million doses of the Johnson & Johnson vaccine have been administered to women under the age of 50, so if the risk is high only for that group, the incidence is around one in 250,000. Pregnancy, using hormonal contraceptives and smoking all are associated with a much higher risk of this form of blood clotting than even crude estimates of the vaccine-related risk for clotting. The odds of having a blood clotting disorder as a result of having Covid-19 is much higher, affecting as many as one in five hospitalized patients.

This means that if you received this vaccine and you are under 50, the odds are in your favor.

If you were counting on getting the Johnson & Johnson vaccine, bear in mind that the pause has been extended, but it is not permanent. In addition, we were already contending with projected low supplies of the Johnson & Johnson vaccine because of manufacturing problems, and many states were already looking at alternatives. The United States is in the fortunate position of already having supply of two other Covid-19 vaccines that are also highly effective and safe, so this pause should not substantively impact the vaccination rollout over the long-term.

I am not losing sleep over my decision to get the Johnson & Johnson vaccine. The pause and the resulting careful, transparent deliberation shows our regulatory systems are robust and cautious.

The investigation has empowered me with information about what to do in the very unlikely event that I do develop symptoms of a stroke — I told my husband to tell the doctor not to give me heparin — and I am reassured by understanding that my relative risk is incredibly low, while the benefits of being vaccinated are immense.

Angela L. Rasmussen (@angie_rasmussen) is a virologist at the Center for Global Health Science and Security at Georgetown University Medical Center. She studies the host response to infection with emerging viruses, including the coronavirus.

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