With the news that the CDC and FDA have called for pausing the rollout of Johnson & Johnson’s single-injection COVID-19 vaccine due to extremely rare cases of blood clots, some have been drawing comparisons to the blood clot risk from hormonal birth control.
But while the Pill is known to increase risk for blood clots, three doctors who spoke with BuzzFeed News said these are two very different scenarios.
"It’s not only not apples to apples, it’s basically apples to papayas. It is completely different," said Hanny al-Samkari, an assistant professor of medicine at Harvard Medical School and a hematologist and clinical investigator at Massachusetts General Hospital. "Yes, they both can cause clots — just like apples and papayas are both fruits — but the mechanisms are totally different."
On Tuesday, the pause on the Johnson & Johnson vaccine was recommended after six women between the ages of 18 and 48 developed a rare type of blood clot within 13 days of receiving the vaccine. One woman died and another is in critical care, according to the FDA. But approximately 6.85 million doses of the vaccine had been delivered in the US as of April 13, meaning the complication appears to affect fewer than 1 in a million recipients.
These extremely rare blood clots are of a severe kind that appear to significantly raise the risk of a stroke. Al-Samkari noted that the key characteristic of these clots is a drop in blood platelet counts. Crucially, unlike other blood clots, the blood-thinning medication heparin is a dangerous treatment for patients with these clots.
The rare clotting appears to be similar to what’s been seen in approximately 1 in 100,000 patients who received the AstraZeneca vaccine, which uses the same technology to immunize people against the disease caused by the coronavirus. The Pfizer and Moderna shots, which are also authorized in the US, use a different approach and have not resulted in any reports of blood clots, according to the FDA.
While the clotting risk appears to be extremely low with the Johnson & Johnson vaccine, a flurry of tweets has compared it to the risk of blood clots from hormonal birth control pills. According to the FDA, for every 10,000 women taking the Pill in a given year, between 3 and 9 will develop a blood clot, compared to between 1 and 5 women who are neither taking the Pill nor are pregnant.
But, crucially, it's not the same clotting as that experienced by some with the Johnson & Johnson vaccine.
"They could not be more different when we talk about the underlying mechanism," said al-Samkari.
The typical blood clot linked to birth control is called deep vein thrombosis, a clot that develops in the leg but can break off and travel to the lungs. Those are usually treated with blood thinners.
Federal health officials on Tuesday said part of the intent of the pause is to wave off that typical treatment in patients who received the Johnson & Johnson shot because it is ineffective on the linked blood clots. “This [pause] is important to ensure that the health care provider community is aware of the potential for these adverse events and can plan due to the unique treatment required with this type of blood clot,” the FDA said.
Jeff Weitz, a thrombosis expert and professor at McMaster University in Ontario, Canada, said another difference between the types of clotting was that someone with an underlying hereditary condition who takes the Pill can be more at risk for clotting.
The FDA has noted that although the six women in the US who had serious clots after the Johnson & Johnson vaccine were of reproductive age, no known evidence links birth control use to an increased risk of a blood clot caused by this particular shot.
According to information presented by the CDC on Wednesday, one of the six women was taking a combination birth control pill, and none were pregnant or postpartum.
Based on those six cases, the risk of a blood clot issue from the vaccine remains much lower than that from taking hormonal birth control.
That has some people wondering why there's been so much concern over the Johnson & Johnson vaccine when so many millions of people take hormonal birth control every day. The reason is that vaccines, especially for shots newly authorized on an emergency basis, have a higher safety requirement than other medicines that have long been in use.
"This is part of the robust monitoring system that we have in the United States,” said Jennifer Lighter, an infectious diseases specialist and hospital epidemiologist at NYU Langone Health. “This is a good thing that we take serious adverse effects very seriously, and we pause and investigate. That’s what you want in a country that rolls out a new vaccine or medication."
Lighter pointed out that the risk of dying from COVID-19 — more than 563,000 deaths in the US have been attributed to the disease — remains much higher than any risk of fatal complications after receiving a vaccine of any type.
Al-Samkari said anyone who has received the Johnson & Johnson or AstraZeneca vaccine, particularly young women, should talk to a doctor if they "start developing any significant, severe untoward symptom." He said symptoms like severe headache, sharp leg pains, or changes to the senses or nervous system that come on suddenly should be checked out.
"If it’s unusual and it’s out of the blue and it’s severe and it doesn’t go away, that’s when you want to see your doctor and get it evaluated immediately," he said. (People who had the shot a month ago are in the clear, federal health officials noted, because symptoms would have developed by now. The concern is chiefly among people who got the shot within the last few weeks.)
Al-Samkari added that the precautions taken by regulators shouldn't scare people or make them hesitant to get vaccinated — quite the opposite.
"The main message I tell people after seeing this is this should make everyone feel very comfortable," he said. "If something was happening potentially related to a vaccination and our regulators were ignoring it or waving it off, that would be the danger place, that would be food for the anti-vaxxers. Things are happening just exactly as we want them to."