MEDICAL MONDAY: Blood Clots and AstraZeneca's COVID-19 Vaccine

CBSN Bay Area talks to Stanford Health Care's Dr. Malathi Srinivasan about the rare reports of blood clots linked to the AstraZeneca COVID vaccine and if that would affect the U.S. rollout.

Video Transcript

MICHELLE GRIEGO: Right now, the rollout of the AstraZeneca vaccine is on pause in several European countries because of concerns over blood clots. Dr. Malathi Srinivasan with Stanford Health Care joins us now with more on that. So what do we know about those cases?

MALATHI SRINIVASAN: Michelle, what we know is that the AstraZeneca vaccine has been given to 20 million people in the European Union and in the UK. And of those people, of 20 million people, seven people have had blood clots in multiple vessels. And then eight have had a rare form of blood clot in the brain, in the veins of the brain. And so most of these have been under people under 55, and most of them have been women. And of those people, nine people have died.

This appears to be a very rare complication of the AstraZeneca vaccine. And we need to keep this in perspective. Around the world, there are over 2 and 1/2 million people who have died of COVID so far. And the normal background rate of people having blood clots is somewhere in the US like a one to two cases per 1,000 people. And every year over 100,000 people die of blood clots in the legs and in the lungs.

So when we're thinking about any kind of therapeutic, it's important to weigh the risks and benefits. And right now, the World Health Organization has a global advisory committee on vaccine safety that's taking a look at the vaccine data, and currently is recommending to go ahead with vaccine because the rate of these complications is so low. But they'll be a little bit more coming out I think in the next couple of weeks in terms of final recommendations.

MICHELLE GRIEGO: Yeah, we'll definitely be on the lookout for that. You know, the question is, is could this all potentially delay the approval of the AstraZeneca vaccine here in the US?

MALATHI SRINIVASAN: Yeah, I don't think it's going to delay the approval of the vaccine. The FDA has a very strong independent processes of evaluating vaccine safety. And right now, the FDA is taking a look at the 30,000-person trial that was conducted in the United States and should be coming up with recommendations in a week or two.

MICHELLE GRIEGO: So as the variants continue to spread, how long could it take to conduct trials for the vaccines modified to combat those variants?

MALATHI SRINIVASAN: So Michelle, we have very good news on that front. Last week, the FDA came out with a whole new slate of recommendations on how to accelerate vaccine development, as well as therapeutics. And for vaccines, they're starting to treat the vaccines, and the new vaccine rollout, much like we do for the yearly influenza vaccine. So the trials will be shorter, and be looking for safety. And probably after a new vaccine is developed, within three to five months we should have enough data to know whether it's safe or not.

Now, this is a really big deal because, as you know, the first set of trials took hundreds of thousands of people to be able to demonstrate whether it worked or not, and how safe it was. And we know that the mRNA companies, for instance-- the Moderna and the Pfizer vaccine-- are able to generate new vaccine prototypes within about six weeks. So we can actually have a fairly rapid response to the emerging variants that are escaping the current immunoglobulins that we're producing in response to the vaccine.

MICHELLE GRIEGO: Very interesting, there. There's also a new FDA approved test. It's called T-Detect. What does that test look for?

MALATHI SRINIVASAN: Well, Michelle, T-Detect is a great example of advances in precision medicine. And what it does, is it looks at the DNA in a cell type called T cells in people's blood, and the T cells are part of our immune system. So whereas B cells make the proteins called immunoglobulins, T cells actually fight the virus itself. And so the good news here is that it seems to be a pretty sensitive test. It detects the DNA in these T cells that affects-- that is ramped up by the COVID virus, and it can pick up responses for up to six months after an infection. So if you don't know whether or not you had COVID, and you're having symptoms, say of COVID long-haul syndrome within your logic and the cardiovascular complications, or just the generalized fatigue, then you can get this test and see if you had been infected with COVID in the past.

The immunoglobulins are only lasting for a couple of months with native infections, and sometimes the levels are very low. But this appears to have a longer lasting detection in the blood, and certainly the T cells are also part of our immune system. And much like some of our other memory cells, they sit around, and once they've been primed, they can be reactivated by a new infection.

MICHELLE GRIEGO: All right. Well, so much good information there. Dr. Malathi Srinivasan with Stanford Health Care. Thank you.

MALATHI SRINIVASAN: Thank you so much, Michelle. Great to see you.

MICHELLE GRIEGO: Great to see you.