COVID, Quickly, Episode 5: Vaccine Safety in Pregnancy, Blood Clots, and Long-Haul Realities

T: Hi, and welcome to Covid, Quickly, a Scientific American podcast series!

J: This is your fast-track update on the COVID pandemic. We bring you up to speed on the science behind the most urgent questions about the virus and the disease. We demystify the research, and help you understand what it really means.

T: I’m Tanya Lewis

J: I’m Josh Fischman

T. And we’re Scientific American’s senior health editors. Today, we’ll talk about why COVID vaccines seem safe for pregnancy …

J: And the rarity of blood clots with the Johnson and Johnson vaccine…

T: And the first strong data showing that COVID still hurts many people months after they first got sick.

T. Parents-to-be have worried about the safety of COVID vaccines for pregnancy. Josh, this week there’s some reassurance, right? 

J: Yes there’s some good news. A study of about 35,000 pregnant women, done from December 2020 through February of this year, found they reported no extra problems. They had the same levels of side effects that non-pregnant women had: soreness in the arm where they got the shot, fatigue, and headaches.

A small group of these women, just over 800 of them, finished their pregnancies during the study. And again the result paralleled the general population. 86 percent of pregnancies resulted in live births. Rates of miscarriage, birth defects, preemie births, and low birth weights were very close to what women experienced before the pandemic hit us.

Now there are some limits to this research, which came out this week in the New England Journal of Medicine. People volunteered to report their conditions to a federal government web site, so maybe those with serious problems were not among the volunteers. In several months, a broader look at actual medical records could give a more complete picture. Still, before this we really didn’t know anything about the safety of these vaccines in pregnancy. Now we do, and expecting parents can feel better about getting their shots.

J: Last week, U.S. health agencies recommended a “pause” on use of the J&J vaccine because of several extremely rare reports of blood clots. What’s going on with that?

T: Well, only six people had this condition out of about 7 million, so the risk of it happening is extremely rare, but the CDC and FDA made the decision to pause vaccinations “out of an abundance of caution.” 

These blood clots aren’t quite like normal blood clots, though—they seem to occur in combination with low numbers of platelets, the parts of blood involved in clotting. While blood clots themselves are quite common, this particular combination of symptoms is very rare. It resembles a condition known as Heparin-induced thrombotic thrombocytopenia, which occurs occasionally with the blood-thinner Heparin.

Another vaccine, made by AstraZeneca, had been linked to this rare blood clotting condition in a very small number of individuals in Europe, leading to a similar pause there. 

Both vaccines are made with adenoviruses, so it’s possible there is a similar mechanism at play.  But scientists have cautioned that the risk of these clots is still extremely low, especially compared with the risk from COVID. 

J: Is holding off going to increase vaccine hesitancy among some people?

T: Some critics think so. But other scientists say this is exactly how the system is supposed to work—that by taking these rare events seriously, the CDC and FDA are cultivating more trust with Americans. There’s another argument for the pause—it notifies doctors to look out for patients with these rare reactions, so they can be treated. 

The signs of blood clots are things like an extremely persistent headache, abdominal pain, leg pain, or shortness of breath within 1-2 weeks of vaccination. Also, there’s evidence that the normal treatment for these clots, a blood thinner like Heparin, may make it worse. There are other treatments doctors should give instead.

The Pfizer and Moderna vaccines haven’t been linked to clots. For Johnson and Johnson, a CDC advisory committee is set to meet today to discuss the pause. They may decide to lift the pause and possibly issue a warning about the clots, as Europe has done, or they may extend the pause until they have more data. 

T: For the past year we’ve heard a few stories about “long haulers,” people struggling months after their initial bout of COVID. But this week, we got some strong evidence showing just how serious this is, right?

J: We have data drawn from more than 70,000 COVID patients, followed for six months after their initial illness. Some of these people remain really sick. This isn’t a bunch of anecdotes. This is A strong pattern. And it can be deadly, too.

The patients were all in the Veteran’s Administration health system, so they have detailed records. Compared with non-COVID patients, they had a 59 percent higher risk of death during those six months. A whole slew of medical problems cropped up during that time. Heart attacks, respiratory failure, diabetes, neurological problems, anxiety, and more. These patients kept showing up in doctor’s offices, and used more medications. There was also a higher rate of opioid use. Not everyone runs into these problems, but they’re real.

And here’s a striking comparison. You know how people say “Oh, COVID is just like a flu”? No. It’s worse. This data, published this week in the journal Nature, compared COVID patients to flu patients. The flu patients had lower levels of all the illnesses I just mentioned. And COVID patients were more likely to die during that half-year. About 50 percent more likely. For some patients, the initial infection isn’t the  end of their problems.  

T: Now you’re up to speed. Thanks for joining us. 

J: Come back in two weeks for the next episode of COVID, Quickly! And check out for updated and in-depth COVID news.

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