Vaccine and transmission…

Once you get the vaccine (or a natural infection), it’s really important you continue to wear a mask, social distance, wash hands, etc. Let me (try to) explain.

We know the Pfizer and Moderna vaccine protects you (ie the person that gets the vaccine) against disease. We know this from the high efficacy numbers (95%) and our antibody studies thus far (see previous posts). In other words, if you get the vaccine and come in contact with COVID19, your body will know how to fight the virus and your immune system doesn’t get overwhelmed and go crazy (ie fever, respiratory issues, and potentially the ICU).

We do NOT know whether a vaccinated person (or person with a previous covid infection) can still host the disease and continue to spread it. In other words, if you get the vaccine and come in contact with COVID19, you MIGHT be able to still harbor the virus. Then, if you come into contact with someone else who doesn’t have the vaccine, you give them the virus. This is worst case scenario. We HOPE that we have sterilizing immunity, in which the COVID19 antibodies protect from both disease (ie symptoms) AND transmission. We just don’t know yet.

Since people asked yesterday, not all vaccines produce sterilizing immunity, but they don’t need to in order to be effective at preventing disease (i.e. symptoms and illness). For example, the polio vaccine does not induce a sterilizing immune response but is still 90% effective. On the other hand, the HPV vaccine does prevent transmission.

Moderna is testing whether we have sterilizing immunity after the COVID19 vaccine. They do this by testing everyone for COVID19 every few weeks (instead of just symptomatic people) AND they do this by testing for a unique antibody called a neutralizing antibody. So far, there are two small hints that we may have sterilizing immunity after a vaccine:

  1. In the middle of their trial (called an interim analysis), Moderna tested 34 people for neutralizing antibodies over time. 119 days after the vaccine, everyone still had these antibodies. The number of neutralizing antibodies decreased a little, but that’s expected. These results were published in the New England Journal of Medicine (the most predominant journal in medicine)
  2. In the FDA Moderna report yesterday, another small hint was reported. While Moderna’s full analysis wasn’t complete, they wanted to give a glimpse of the data so included it in their addendum (ie not the full report for their application for emergency use). Moderna reported that 38 people in the placebo group had asymptomatic infection while 14 in the vaccine group had asymptomatic infection. This is an indirect, proxy analysis. It’s certainly not as good as testing antibodies, but is a hint.

These are small studies. And, like everything else, we need more data. We want to be sure that these findings are meaningful (and not random). Moderna is working on it. Unfortunately, though, it will be a few months until we know more.

So, in the meantime, continue public health mitigation measures if you do get infected or get the vaccine. We can’t have a mask bonfire yet.

Love, YLE

NEJM publication:

Moderna addendum:


COVID and candles?

Epidemiologists find meaningful patterns in data. That’s our job.

This pandemic has given us the opportunity to find disease patterns in sources I never thought possible. Like stool samples in New York or mobile phone data. But this latest analysis is, by far, the most innovative (and hilarious) I’ve seen.

Enter Amazon reviews. Turns out Yankee Candle company has been getting some bad reviews lately. One budding scientist thought to look into whether this was because of the pandemic, as one of the main symptoms is loss of smell.

So, she downloaded a random subsample of Amazon customer reviews of the 3 most popular scented candles. Between January 2017 to January 2020, the average rating consistently hovered around 4.3 (out of 5). But, interestingly, there was a sharp drop in 2020 (Figure 1).

But correlation doesn’t equal causation. In other words, other things could be causing this drop. She needed a comparison. So, she then downloaded data from the 3 most popular unscented candles on Amazon. There wasn’t nearly as big as a drop (Figure 2).

THEN she downloaded the actual text of the reviews. She used statistical software to search for words like “lack of scent”. Since the beginning of this year, the proportion of reviews mentioning lack of scent grew more than 4% from January 2020 to November 2020.

Absolutely brilliant!

So, before you write a review like this, make sure you don’t have COVID19 first. In fact, epidemiologists should partner with Amazon to send COVID19 testing reminders to “lack of scent” reviews? (I’m half joking).

Love, YLE

Data Source: Check out the young budding Harvard scientist on Twitter (@kate_ptrv). No she’s not an epidemiologist, but maybe I can convince her to apply to our program



This year I’m thankful that the world finally knows that an epidemiologist is not a skin doctor.🙂

Happy Thanksgiving!


Happy Halloween!!!

It’s hard to believe but there are silver linings to this pandemic… Like the sheer amount of creativity and brilliant innovation implemented so we can continue meaningful lives while staying healthy and protecting others. From what I’ve seen so far, Halloween has been no exception.

Today we are turning our front yard into candy land. Hopefully the kiddos find it fun, as they have been through a confusing and heavy rollercoaster this year. And, unbeknownst to them, this little extra step helps protect them and curb community transmission at the same time. It’s a win-win.

I would love to SEE and HEAR the creative things you’ve come up!! This could be simply putting masks on your goblins and witches, finding ways to hand out candy, having a Halloween movie night, or staying home and making cookies. Everyone has their own level of comfort and balance during these unprecedented times.

Stay healthy (and sane) out there!!

Love, YLE


COVID-19 and National Voter Registration Day

Two things…

First, I don’t care who or where you are, register to vote here:

Second, some states allow you register to mail-in-vote online while registering to vote. If you have this option, keep reading…

A few months ago, I was invited to an advisory board to ensure safe voting during the pandemic. This advisory board had 11 people: I was the only epidemiologist (PhD) alongside some of the biggest names in medicine (MDs). We were tasked to define “high risk COVID19 populations” for mail-in voting and put forth safe voting guidelines for in-person voting. While we completed our task, our finalized report has yet to be released; however, I’m authorized to share the list of high-risk COVID19 populations we agreed upon. Every condition on this list is data-driven and evidence-based (you can imagine the long conversations we had over zoom). Also, we attempted to translate the official medical disease name in easier to understand lingo.

IF your state has the option AND you have one of the listed conditions, PLEASE consider mail-in or curbside voting. This will allow you to exercise your right to vote AND your right to good health.

High-risk COVID19 Populations:

Pulmonary (Lung) Conditions

  • Asthma (moderate-to-severe).
  • Chronic Bronchitis.
  • COPD (chronic obstructive pulmonary disease).
  • Cystic fibrosis, a condition that affects the lungs and digestive system, causing a lot of infections and blockage due to secretions.
  • Emphysema.
  • Chronic Lung disease.
  • Pulmonary fibrosis (having damaged or scarred lung tissues).
  • Smoking.

Cardiovascular and Cerebrovascular (Heart and Brain Blood Vessel) Conditions

  • Serious Heart conditions, such as heart failure, coronary artery disease, or cardiomyopathies (diseases of the heart muscle).
  • Cerebrovascular disease: diseases that affect the blood vessels and blood supply to the brain.
  • Stroke.

Diabetes and Hypertension

  • Type 1 or Type 2 Diabetes.
  • Hypertension (high blood pressure).

Weak Immune System

  • Blood or bone marrow transplant.
  • Any type of Cancer.
  • Receiving Clinical trial treatment (drug or medical device) after September 13, 2020.
  • HIV (Human Immunodeficiency Virus).
  • Solid Organ transplant.
  • Use of “Steroid” medications.

Additional Medical Conditions

  • Cirrhosis of the liver.
  • Hemoglobin disorders.
  • Chronic Kidney disease.
  • Liver disease, including cirrhosis.
  • Neurologic conditions, such as dementia.
  • Obesity (body mass index [BMI] of 30 or higher).
  • Pregnancy.
  • Sickle cell disease.
  • Thalassemia.

Age 65 or older

Unfortunately, this is the only information I’m authorized to share thus far. I hope that the formal report will be coming out soon.

Love, YLE  

PS. This is a bipartisan page. We all know who is running. No need to turn the comments section into your personal preference platform. The purpose of this post is to educate people how to safely vote given the public health circumstances.


Origins of COVID-19….

On Sept 14, a scientific article (“Yan report”) was preprinted stating that COVID19 was made in a lab rather than the “natural origin theory” (i.e. jumping from animal to human). The article has been downloaded 539,705 times and was picked up by several news source (some with more than 2 million views on YouTube). The Yan report has NOT been peer reviewed.

The report claimed many things using complex technical jargon. It’s impossible for non-experts to decode the science. However, previous peer-reviewed science can poke a LOT of holes into their claims…

1. Yan report claims COVID19 is similar to two strains of bat coronaviruses (ZC45 and/or ZXC21) that were created by scientists at Chinese military labs. However…

• COVID19 has more than 3500 differences (11%) compared to these two strains, so using them as a blueprint would be, quite literally, a waste of time.

• In July, a peer reviewed article showed the lineage of COVID19 and found its closest ancestor (96% match) was RaTG13 (a virus that’s been circulating among bats for decades)

• We know that COVID19’s cousins exist in nature among many animals. For example, SARS is found in bats. And the cousins have been shown to directly jump from bats to humans.

• Viruses constantly evolve and are passed between species. The Yan report ignored all recent COVID19 data implicating that the virus jumped from bats to pangolins. Viruses are often passed to an intermediate animal, like pangolins, and stay in the intermediate animal until the virus could evolve enough to infect humans.

2. Yan report claims the presence of a “furin cleavage site” on COVID19, which would make the virus more infective than usual. They also claim that cleavage sites are not found on other coronaviruses. Together, this must mean COVID19 was engineered. However, this cleavage site could have been added by combining with another virus (and not added by humans). This happens all the time. It could have happened the day before patient zero was infected or could have happened thousands of years ago. Also, not to mention, similar cleavage sites are found on bat coronaviruses in wild populations.

3. Yan report points out that COVID19 has sites that can be cut and pasted (also called enzymes). These are sometimes found in cloned viruses. However, these sites also naturally occur in ALL types of genes. Also, using enzymes is really a quite outdated way to make a biological weapon…

There are also 3 noteworthy “non-scientific” holes in this article…

1. The writing style was nothing but odd. For example, the study doesn’t start with a hypothesis. Instead, the authors start by stating “It is noteworthy that scientific journals have clearly censored any dissenting opinions that suggest a non-natural origin of SARS-CoV-2. Because of this censorship, articles questioning either the natural origin of SARS-CoV-2 or the actual existence of RaTG13, although of high quality scientifically, can only exist as preprints.” A defensive opening is certainly not a “normal” introduction (or justification) for a scientific study.

2. The authors also use an odd choice of vocabulary throughout. For example, the word “suspicious” is used five times throughout the manuscript. I’ve honestly never seen in a scientific article. Should I say that this is “suspicious” 🙂

3. The scientists state, as they should, their institution: a non-profit called the Rule of Law Society & Rule of Law Foundation located in New York, NY. This non-profit also funded the study (i.e. paid the scientists for their time). After some light googling, it’s clear that the institutes are NOT bi-partisan, scientific think tanks. This brings into question conflicts of interest.

Finding the origin for COVID19 is like looking for a needle in a haystack, as we have to test a huge number of animals and humans in China to trace the evolution. The World Health Organization has already organized a team to lead this.

We will have to be patient while we find the origin of this virus. We will also have to be patient while we wait for the Yan report to be peer reviewed. It’s important to get this right, not only for public health (and preventing future virus jumps) but also because of political, social, and economic implications if we were to get this wrong.

Love, YLE

Andddd here are ALL the data sources… RaTG13 lineage: SARS and bats:;; bats to pangolins:; Furin cleavage sites: ; Finding a needle in a haystack:


Types of Face Masks

In the past, we’ve only used surgical masks during epidemics (think SARS and MERS). We know these work. If you need the science (including a meta-analysis) let me know. But, now that we need masks on a global scale, we are turning to other types (like cloth and bandanas). The only problem is we don’t know how effective they are.

A recent study has gained a LOT of media attention. Some headlines (and actual articles) have spun the science to conclude more than it can prove: “Scientists test 14 types of masks- here are the ones that worked and didn’t”; “Which face masks are the most (and least) effective at stopping COVID19 exposure”. None of these are accurate.

So, what actually happened?

A couple physicists had an important question: Can they use easily accessible equipment to test different face masks? This is called a “proof-of-concept” study. This is an important question because if they can find this equipment, we (epidemiologists) can start running much larger studies to answer the bigger question.

What did they do? They tested 14 masks. For each mask, one person (the same person throughout the entire study) put the mask on and said one sentence. The same person did this 10 times. For a subset of three masks, they brought in 3 other people.

What did they find? The technology works and should be used on a broader scale.

That’s IT.

We cannot make conclusions about how some masks are better than others. We need a far larger sample size, with different types of “talkers” (spitters, loud talkers, etc). We need far more details on the type of masks used in the study. We need a standardized approach to consistently test people with masks (longer breaks, maybe drink some water). Hopefully this is coming.

Translation? We don’t know how effective different face masks are… yet. We CAN make educated guesses but is different than scientific evidence.

The WHO recommends a three layer, material mask. The CDC echos this. The CDC also does NOT recommend face shields in replacement of a mask.

We need to manage our expectations of what scientific studies can and cannot do. We are looking for quick answers. Which I don’t blame given we are in a pandemic. But we also have to be smart about our “scientific translation” to the public too.

Love, your local epidemiologist

Data Source:…/2020/08/07/sciadv.abd3083…

WHO recommendations:…/advice-for-…/when-and-how-to-use-masks

CDC recommendations:…/prevent…/diy-cloth-face-coverings.html


Success story

Always love hearing a successful public health story. I know this helps my colleagues and I (and I hope everyone) keep moving forward and fighting the good fight.

New Zealand has not had one new case of community spread for 100 days. The 3 month mark is a significant milestone in public health: the post-elimination phase. A few NZ public health officials published their experience in the New England Journal of Medicine (impact factor = 70; this is HIGH) over the weekend.

What happened?
-Eliminated COVID19 103 days after the first identified case
-Total case count=1569 (32 per 100,000)
-Total deaths=22 (4.5 per 1 million); the lowest among the 37 Organization for Economic Cooperation and Development countries

What was their approach? Check out their graph. Briefly,
-“Empathetic leadership”
-“Public confidence and adherence”

And, because I know it’s coming… yes, I know NZ is a different country than the US. No, I didn’t make (or attempt to make) any comparisons with the US. This is simply me cheering New Zealand on, as we all should.

Love, your local epidemiologist

Data source: Baker and Anglemyer (2020). Successful elimination of COVID19 transmission in New Zealand. New England Journal of Medicine. 


Science check-list

I usually don’t post on Sundays, but this had me concerned. We are in a new age. Where people are even faking scientific studies.

This “study” has been used many times to justify the use of a COVID19 drug. It’s a professional looking page. The graphs are beautiful. They use big words. They use scientific jargon. If I didn’t know what to look for, I would have been fooled. 

When reading articles, there are a few things you can find to ensure it’s a real scientific, peer reviewed article…

  1. Journal: A study must be published within an academic journal. This ensures it was peer-reviewed. This means the validity of the study was checked by other scientists. Now there ARE “better” journals than others. We rate journals off of “impact factors”. The higher the number, the better the journal. You can easily google the impact factor for any international journal. This article is not listed within an academic journal. 
  2. Authors: A list of authors, their degrees, and their affiliations must be presented right after the title. This article just includes a random twitter handle. 
  3. Human Subjects: The study must be approved by human subjects committee. AND this must be stated within the article. This ensures that the study was ethical. We, scientists, have to go through a LOT of hoops to get our study approved (which is a good thing). This article lists NO human subjects number. 
  4. Conflicts of Interest: The authors must declare conflicts of interest. This gives the reader an idea whether there is potential for biases. There are no listed conflicts of interest.
  5. References: References are used to support claims throughout the paper. This is how we build science on science. Citing wikipedia is unacceptable. This would never fly in an academic journal. This article references wikipedia quite often.
  6. There is also an “under attack” red banner at the top. Which is actually kind of funny. Scientists would NEVER label themselves as under attack within a journal. This would NEVER show up on a legitimate study.

I am all for debating science against science. The danger comes in when we start debating fake science against science. This is how scientists start losing the public’s trust. Science is the only thing we have left in this fight, and whoever wrote this knows that. 

Do you due diligence before reading an article (and certainly before you start sharing with others) by going through this checklist. We can all do our part to stop these things in their tracks. 

Love, your local epidemiologist