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27 Dec, 5 tweets, 2 min read
UPDATE: Vaccinologists like to say they breathe a sigh of relief after 3 million inoculations of a new vaccine. That's when we get a real handle on side effects. We'll soon reach that milestone with mRNA vaccines (Pfizer, Moderna). There's another phenomenon we should follow: 1/
It's important to determine if people are contracting #coronavirus after vaccination. The phase 3 trials that were the basis for emergency authorization looked at prevention of symptomatic disease; they did not assess prevention of transmission. 2/
This means people could, in theory, contract #coronavirus and transmit it to others after vaccination. But is this happening? Thus far, I've only heard of one case of a person contracting the virus after vaccination. (Are there more?) It happened in Texas. 3/
An ER doctor mounted a fever 9 days after vaccination & tested positive for #coronavirus. This shouldn't be alarming; we know it's possible. And it seems extraordinarily rare. But I'm far more interested in this than the occasional allergic reaction. 4/
Takeaway: As we become more comfortable with the very, very rare side effects of #COVID vaccines, we'll turn to other issues. Post-vaccination infection has important implications for public health and basic research. It's a reminder that vaccines aren't an on/off switch.

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Matt McCarthy Profile picture
29 Dec
UPDATE: A #coronavirus patient is considered contagious as long as they carry "replication-competent" virus. Based on limited CDC data, patients with severe immune impairment are thought to be contagious for up to 20 days after onset of COVID19 symptoms. This may soon be revised:
We've known that patients with weakened immune systems can remain contagious for up to twice as long as those without immune impairment (20 days vs. 10 days) and these findings have informed transmission-based precautions around the country.
But 20 days may be insufficient.
A new study of immunocompromised #COVID patients found that some remain potentially contagious far longer than previously thought: 15% had replication-competent virus after 20 days. 
Key finding: 1 patient grew virus in culture 61 days after symptom onset. nejm.org/doi/full/10.10…
Read 6 tweets
Matt McCarthy Profile picture
29 Dec
Hospitalized patients and research subjects often ask me about antibody treatments. They touch on a recurring theme: Many believe these treatments go unused because a) Doctors don't think to order them or b) We don't have the connections to acquire them. Here are key points: 1/
Monoclonal antibodies made by Regeneron and Eli Lilly are not authorized for patients who are hospitalized due to #COVID19. Trials have been stopped because antibodies don't help these patients. Nevertheless, many are distressed they're not being used. 2/
nytimes.com/2020/10/27/wor…
We've recognized the futility of giving antibodies to hospitalized patients for months, but only recently have we understood why: The timing of the antibody response is more important than the amount of antibody.
Early antibody response is crucial. 3/
medrxiv.org/content/10.110…
Read 5 tweets
Matt McCarthy Profile picture
27 Dec
Here are 3 #COVID19 questions we're trying to answer:
1. Why do monoclonal antibodies fail hospitalized patients? Cocktails made by Eli Lilly & Regeneron may be useful for high-risk outpatients, but they don't help hospitalized patients. Why does the treatment setting matter? 1/
Part of this is timing. By the time someone shows up in the ER with symptoms, they may have been infected for a while (incubation is ~6 days). Most COVID treatments fail if they're given late in the course of disease and antibodies are no exception. They should be given early. 2/
But there are other theories to explain the failure: Antibodies may fail to efficiently penetrate the infected tissue of hospitalized patients. Or coronavirus may mutate to evade the monoclonal antibodies (these are called escape mutations). 3/
pubmed.ncbi.nlm.nih.gov/32540904/
Read 10 tweets
Matt McCarthy Profile picture
24 Dec
COVID question doctors are wrestling with: Should patients with profoundly impaired immune systems receive monoclonal antibody therapies after contracting #coronavirus? 1/
These patients are often prioritized for antibody treatments (made by Regeneron and Eli Lilly). And this makes sense: Their immune systems are weak, and antibodies can potentially help fight infections. But there's an issue. 2/
A new hypothesis argues that patients with weak immune systems could serve as an incubator for viral mutations, leading to new strains like B.1.1. 7 that might be more transmissible. 3/
Read 8 tweets
Matt McCarthy Profile picture
23 Dec
UPDATE: Coronavirus has mutated into a new variant, B.1.1.7, that has the world's attention because it may be more contagious.
Some thoughts on where this came from and how it impacts patient care: 1/
The novel #coronavirus typically acquires a mutation every few weeks. The new variant is interesting because it seemingly developed a bunch mutations all at once: 17 mutations in viral proteins, including 8 changes in spike protein, the target for all of our vaccines. 2/
Why would a flurry of mutations suddenly emerge? The focus now is less on unique properties of #coronavirus and more on unique human hosts: patients with impaired immune systems who are chronically infected and unable to clear the virus. 3/
sciencemag.org/news/2020/12/u…
Read 10 tweets
Matt McCarthy Profile picture
22 Dec
Here's one of the points I made in this #COVID19 lecture: When I see a politician taking drastic action that is not supported by data, I ask myself, "How did this person respond to warnings in March?"
An example: 1/
While most of the world was focused on mitigation in mid-March, the United Kingdom implemented “delay.” As many experts noted at the time, this was a mistake. The UK inadvertently served as the placebo-controlled arm of a global study aimed at limiting death and disease. 2/
Delay has been widely criticized. Coronavirus moved unchecked throughout England until the prime minister was forced to reverse course and implement harsh restrictions. We're still feeling the repercussions today. 3/
bloomberg.com/news/features/…
Read 5 tweets

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