1/ Apologies for not posting this sooner. I've been tied up juggling multiple jobs (Bellevue + media + congressional testimony + other), but I think it's important to get this out there now. I could have last night, but...

2/ The Food and Drug Administration and Centers for Disease Control and Prevention called for a pause on use of the J&J vaccine in this country. Six cases of blood clots have been reported among a million women between the ages of 18 and 48 who have received the vaccine.

3/ To put this in context, women who are not taking birth control pills have a 1 to 5 in 10,000 per year risk of getting a blood clot. This risk increases by more than 4x during and immediately after pregnancy.

4/ Putting this another way: pregnancy increases a woman’s risk of a blood clot by 400 times more than does getting the Johnson and Johnson vaccine. Meanwhile an estimated 1 in 5 people hospitalized for COVID develop blood clots.

5/ It’s normal for people to worry, but we’re really bad at weighing risks. We tend to overemphasize the risk of an action, like getting vaccinated, and underemphasize the risk of inaction, like not wearing a mask in a pandemic or not wearing your seatbelt in the car.

6/ We worry about the risks of something new, like vaccines, but play down the risks we’re used to, like getting in a car accident while driving to work.

7/ The blood clots observed among these six women who received the J&J vaccine are similar to those seen among patients in Europe after receiving the AstraZeneca COVID vaccine.

8/ Both vaccines are based on modified adenoviruses, as are the Russian Sputnik V vaccine and the Chinese CanSino vaccine. Adenoviruses cause the common cold, but the adenoviruses in these vaccines have been “gutted” so can’t replicate.

9/ They’ve been modified to deliver the recipe for SARS-CoV-2 spike protein to human cells. When our immune system sees the spike protein, it learns to recognize SARS-CoV-2 and fight it off.

10/ Many of us now wonder whether the adenovirus vectors (what we call these “gutted” adenoviruses) could be setting off an abnormal immune response that causes low platelet counts and blood clots, what some are now calling “vaccine-induced immune thrombotic thrombocytopenia.”

11/ Heparin, commonly used to treat blood clots, can also rarely cause similar complications. Vaccine Adverse Event Reporting System (VAERS), which is co-sponsored by the CDC & FDA, should be commended for their careful surveillance for side-effects related to the COVID vaccines.

12/ These blood clots are so rare that they weren’t detected in large clinical trials involving tens of thousands of participants across three continents.

13/ Some have criticized the FDA and CDC for recommending a pause on use of the Johnson and Johnson vaccine in the United States. To be clear: the FDA didn’t revoke its emergency use authorization for the J&J vaccine. It didn’t take the vaccine off the market.

14/ And healthcare providers are still free to administer the Johnson and Johnson vaccine after discussing the potential risks and benefits with their patients.

15/ Firstly, the FDA and CDC had to inform the public of these possible side-effects so that patients, doctors, and other healthcare providers know what to be on the lookout for and how to treat complications.

16/ It’s common and normal for people to experience headache, fatigue, fevers, chills, and muscle pain in the first couple days after vaccination.

17/ But if someone has headache, abdominal pain, leg pain, or shortness of breath one or two weeks after vaccination, that’s cause for concern, and clinicians should screen such patients for blood clots.

18/ When we as healthcare providers care for a patient with a blood clot, the first drug we usually reach for is heparin. But heparin is the wrong treatment here. In this setting, heparin could make things worse and could even be deadly.

19/ Remember, heparin can cause a similar syndrome, but the good news is that we have many other drugs to choose from.

20/ Secondly, it’s essential that the FDA and CDC prove themselves to be trustworthy. Worries about vaccine safety and efficacy and a lack of trust in the health system and government drive low confidence in vaccines.

21/ It is essential that the FDA & CDC demonstrate to the public that they are taking seriously any risk, even the most miniscule, & continuously evaluating vaccine safety & efficacy honestly, rigorously, & transparently. By dismissing any risk, we could fuel greater mistrust.

22/ The CDC and FDA may conclude that the Johnson and Johnson vaccine is indeed safe and effective and may recommend lifting the current pause.

23/ They may also recommend restricting use of the Johnson and Johnson vaccine to men and older adults only, similar to restrictions on the AstraZeneca vaccine in Europe.

24/ The CDC’s Advisory Committee on Immunization Practices is reviewing data on the RARE cases of blood clots observed after administration of the Johnson and Johnson vaccine.

25/ Either way, use of the J&J vaccine may fizzle out in this country. Some saw the J&J vaccine as being an inferior product, with lower efficacy against infection and milder disease in clinical trials.

26/ But it’s important to note that the Johnson and Johnson vaccine was studied in South Africa and Latin America, when the B.1.351 and P.1 variants were already each widespread, respectively.

27/ Natural infection is less protective vs both these variants, and the immune responses elicited by vaccination are relatively less powerful against them.

28/ Neither the Pfizer nor Moderna vaccines were subjected to the same stress test in clinical trials, but the mainstream media headlines didn’t communicate this nuance.

29/ In the near term, the U.S. supply of the J&J vaccine is likely to be limited due to manufacturing problems at the Emergent Biosolutions plant.

30/ We are fortunate in this country to have multiple highly effective COVID vaccines at our disposal and in ample supply.

31/ ~180M doses of the Pfizer & Moderna COVID vaccines have been administered in this country to date, and we have not seen blood clots associated with either of those vaccines.

32/ Pfizer & Moderna vaccines are based on a different technology. We will have enough supply of both of these vaccines to vaccinate all adults in this country on the Biden administration’s schedule.

33/ What worries me is what this will mean for the global COVID vaccine supply. We were counting on the AstraZeneca, J&J, & other adenovirus vector vaccines—which are cheap and don’t have strict cold storage requirements—to vaccinate the rest of the world.

34/ Last month, in an unprecedented collaboration between competing pharmaceutical companies, Merck announced that it would help J&J scale up production of its COVID vaccine.

35/ This vaccine supply won’t come in time to vaccinate Americans, but it's essential to the global COVID vaccine effort.