Zoe Berg, Photo Editor

On Tuesday morning, the Centers for Disease Control and Prevention and the Food and Drug Administration issued a joint recommendation for states to stop administering the Johnson & Johnson COVID-19 vaccine “out of an abundance of caution.” Shortly afterward, the Connecticut Department of Public Health and the city of New Haven announced that they will pause administration of the Johnson & Johnson COVID-19 vaccine.

The pause of J&J vaccine administration follows the emergence of isolated cases of central venous sinus thrombosis — a condition whereby blood clots form in the brain — in six women between the ages of 18 and 48 who had received the Johnson & Johnson shot. According to the CDC, as of Tuesday, over seven million people have received this vaccine, making the incidence of this phenomenon less than one in a million so far. Health officials and scientists told the News that they have not identified a causal relationship between the J&J vaccine and the blood clots, and that the occurrence is not a cause for general concern.

The Yale New Haven Health System, which provides vaccines to Connecticut residents including Yale students, has suspended use of the J&J vaccine and switched all appointments to the Pfizer or Moderna shots as of Tuesday. Because Yale Health, which provides vaccines to members of the Yale community and Yale Health members, has not yet received any J&J vaccines, it has been unaffected by the directive. But Yale students, who have scoured the state for vaccine appointments since April 1, may experience difficulties in securing an appointment due to the disruption to vaccine rollout.

“All upcoming J&J vaccinations have been paused,” Paul Genecin, chief executive officer of Yale Health, wrote in an email to the Yale community Tuesday evening. “If you are currently scheduled to receive a J&J vaccine, we encourage you to check with your vaccination site to see if it is possible for the site to provide you with either the Moderna or Pfizer vaccine. Alternatively, you may choose to look for an appointment at another site.”

Yale Health has not yet received any J&J shots. Last Monday, Nanci Fortgang, director of Yale’s Vaccination Program, told the News that Yale Health had not received any COVID-19 vaccines from the state through direct allocation for that week. Instead, Yale Health had to obtain shots indirectly through the Yale New Haven Health system. According to Jennifer McCarthy, chief medical officer for Yale Health, the same happened again this week. 

Still, the disruptive impact that this pause has on ongoing vaccination plans across the county is “unfortunate,” according to McCarthy. She said that Yale Health awaits an update from the state on vaccine supply.

According to an email obtained by the News sent to those who had vaccine appointments at YNHHS, people who were scheduled to receive the J&J vaccine at one of YNHHS sites this week were alerted that, depending on the date and location of their appointment, they would get either a Pfizer or Moderna shot instead.

Richard Martinello, YNHH medical director for infection prevention, said the J&J doses are staying in storage for the time being. The pause allows the government agencies to scrutinize the data to try to determine whether the blood clots are merely a coincidence, Martinello said. If they find the vaccine caused the blood clots, they will next scrutinize whether the vaccine is potentially too dangerous for some or all populations. Otherwise, they will restart use of the vaccines, although the exact timeline for the pause is currently unknown.

“It’s really out of being cautious,” Martinello said. “This is the way the safety system is supposed to work.”

Genecin emphasized in his email that safety checks, like the pause on J&J vaccine administration, are an intrinsic part of the United States’ “national safety monitoring program for vaccines.” Therefore, this sort of pause should not be interpreted with alarm — rather, it should be taken as assurance that even extremely rare medical events are being carefully analysed to ensure people’s safety, he explained.

The CDC and the FDA disclosed that those who had cases of central venous sinus thrombosis following vaccination from the J&J shot also had low levels of platelets — which are blood proteins that help the body form clots in the event of bleeding — after these events, which happened from six to 13 days after vaccination. 

“[Central venous sinus thrombosis] are serious blood clots that can cause headaches, vision loss and even strokes, so I agree with the CDC and FDA action to pause the J&J vaccine until more information is available,” Reshma Narula, assistant professor of neurology and the program director for the Yale Neurovascular Fellowship Program, told the News. “[But] I want to emphasize that it is too early to say whether the vaccine caused the blood clots.”

Narula explained that this type of blood clot occurs spontaneously in approximately 15 out of a million people every year, and is more likely to occur in women. On Tuesday, for example, Narula saw patients in the clinic who had experienced this phenomenon without having gotten this particular COVID-19 vaccine.

“These events were very rare,” Narula said. “But as we continue to learn more people who have received the J&J vaccine should remain vigilant and seek care for any new or concerning symptom.”

In July of last year, Hyung Chun, associate professor and cardiologist at the School of Medicine, coauthored a study, published in The Lancet Hematology, on blood clots that may arise in COVID-19 patients. This research helped establish a connection between COVID-19 infection and coagulopathies, a process whereby blood clots can form throughout the body.

Since experts now know that blood clots can form in the brains of people infected with COVID-19, it is important for this potential association with the vaccine to also be closely examined, Narula said.

Although Chun believes this pause should not create panic, he stressed that those who have gotten the vaccine — and the general public as well, since anyone could experience this phenomenon — should be mindful of possible symptoms associated with blood clots, such as swelling in the leg, dizziness, numbing, difficulty breathing and chest pain.

Genecin offered similar guidance in his Tuesday email, encouraging those who experience these symptoms within three weeks of receiving the J&J shot to contact their healthcare providers. He also underscored that this condition is “exceedingly unlikely” four or more weeks after vaccination. 

Henry Rinder, professor of hematology and laboratory medicine, also pointed out that the FDA’s decision to take a pause to evaluate these cases could allow time for government agencies to make treatment and monitoring recommendations for these conditions.

“Today’s decision by the FDA and the CDC highlights the challenges of developing safe and effective therapies as quickly as possible in the setting of a global pandemic,” Chun wrote in an email to the News. “The pause on J&J COVID-19 vaccine distribution, despite such a rare number of cases of blood clots, was properly handled in my opinion to give the agencies time to review the clinical data as thoroughly as possible.”

Over 100,000 Connecticut residents have received the Johnson & Johnson vaccine, and none have reported the adverse effect, Martinello said. But one potential effect of the pause could be increased vaccine hesitancy among those who have not yet received a shot. 

“There is a real risk from this that it foments mistrust in the safety of the vaccine,” Martinello, who sits on Yale’s Public Health Advisory Committee, said. “But I think really the opposite should be true. Groups are out there looking at the data that’s being generated and they’re being very cautious. This was only six people out of seven million, but that was enough to put a hold on things.”

Dean of Public Health Sten Vermund also said that the pause is reassuring. It allows the FDA and company to assess whether certain populations should seek other products, or at least to carefully monitor them for complications. By selecting alternative vaccines for at-risk subgroups, the complications might be managed or mitigated, Vermund added.

The J&J vaccine was seen as a potential game-changer — especially for college students and others who may not be able to arrange for two shots — because it requires only a single dose.

Rose Horowitch | rose.horowitch@yale.edu

Maria Fernanda Pacheco | maria.pacheco@yale.edu

Rose Horowitch covers Woodbridge Hall. She previously covered sustainability and the University's COVID-19 response. She is a sophomore in Davenport College majoring in history.
Maria Fernanda Pacheco is a staff reporter for the Science & Technology desk of the Yale Daily News. Originally from Rio de Janeiro, Brazil, she is a sophomore in Grace Hopper College majoring in Neuroscience and participating in the Global Health Studies program.