Michael Mina Profile picture
Epidemiologist, Immunologist, Pathologist, MD,PhD. Vaccines, immunity, Infectious disease, tests, public health. Previously Harvard Faculty. CSO @eMedCertified
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Oct 15 4 tweets 1 min read

SARS2, like any *Seasonal* corona is...SEASONAL & the season is approaching

We've known since before SARS2 - in many places (incl US) Sept/Oct are lowest months for spread

Assume a rough winter

Plan ahead

We know what's in store (Especially w BQ.1 on rise) Past vaccines and past infections will massively improve outcomes of new infections compared to prior winters where much less immunity existed

I do not feel this is in question

However, w variants like BQ.1, we cant assume much of transmission slowing (perhaps opposite)

Oct 6 8 tweets 3 min read
Please Note:

YES! The current rapid tests *DO* detect all known COVID-19 variants - including BA.5

This terrific paper from @EmoryUniversity and @NIH RADx did a great job at exhaustively evaluating this question AND


cell.com/cell/fulltext/… The researchers did an amazing job at detailing predictions of what mutations that may come in the future (if any) would be likely to evade a rapid antigen test that detects Nucleocapsid of the virus

Sep 16 15 tweets 7 min read

Finally we have an Omicron vaccine!

A vax that many unvaccinated ppl have been waiting for

But, there's a SERIOUS problem in US!

You canNOT get the life-saving Omicron vax if you didnt get the original vax!

This is unscientific policy

fda.gov/emergency-prep… That's right

For ppl who have held out on getting vax'd until an updated vaccine arrived

They canNOT get vaccinated in US w the updated vaccine

In era of Omicron, the very ppl who may benefit most from an Omicron vax are prohibited from it!

There is no scientific basis

Sep 5 10 tweets 2 min read
"We're on a Pandemic Off-Ramp – built upon Immunity from infections & vax"

I've discussed this a lot
Its been misunderstood

We are NOT on a COVID Off-ramp

SARS-2 isnt leaving us

I mean we should be OK shifting to tools for COVID, even if not Pandemic response

A short 🧵

The off ramp we are on is the only off ramp we've ever had

Its built upon Immunity

It's built upon understanding the virus

It's built upon massively reducing many critical urgencies imposed by the pandemic

But like other non-pandemic viruses, COVID is NOT over

Sep 5 4 tweets 2 min read
@mbrushstocks In my view the pandemic has rightly shifted

We've been on the pandemic off-ramp for a while now

It's the only off-ramp we've ever had - built from layers of immunity from vaccines & infections
We're still on it
Older individuals today may never fully exit high risk of COVID
@mbrushstocks We still have pandemic levels of cases, in my view

But doesn't mean we need all the programs (like testing sites) we once had

Today, we must focus more on more precise individual/medicine focused approaches

Get treatment when needed
Get vax'd

A graded approach to exiting

Aug 27 9 tweets 2 min read

Can PCR have a false Negative?

The answer is YES

Q: But why don’t we hear about them?

A: Bc PCR is always given the status of “ground truth” - so it can “do no wrong”

Ex: If rapid test is correctly Pos but PCR Neg, Rapid is automatically assumed to be False Pos

1/ This is important for people to understand, bc it is so rarely discussed

There are in fact many reasons a PCR can be falsely Neg

CDC showed that sampling site alone is important ~5% of Pos nasal swabs were Neg when swab was NP. ~8% or Pos NP were Neg on nasal, etc

Aug 23 14 tweets 4 min read


This is one of the Biggest OVERSIGHTS of the pandemic w MAJOR consequence

This new Paper is a good example of this:

We MUST consider that Incubation period Depends on Immune Status!

jamanetwork.com/journals/jaman… Incubation Period (often defined as "Time from Exposure to Start of Symptoms"

is critical bc it helps:

Dictate quarantine & testing practices
Estimates outbreak trajectory
Allocate Resources, etc

But Symptoms START for 2 totally different & OPPOSING reasons...

Aug 16 7 tweets 2 min read

Important question/scenario here!

70yr old. Vax’d & previously boosted

Up for a new boost BUT got COVID 4 weeks ago

Still get the new booster??

My answer is, No, wait

The immune system was just “super boosted” w the infection and it’s still processing & “learning”

1/ We know from decades of Immunology research how the immune system works + lots of research specifically on COVID

An infection usually leads to a cascade of “classes… beginner to advanced” for your immune system. Even moreso than vaccines. So a recent infection does “count”

Aug 12 25 tweets 9 min read
Remarkable day for COVID #rapidtests


FDA finally recognized Sensitivity of test *REGIMEN* is as/more important than single test

Sort of recognized virus load goes up & impacts Rapid Tests!

Sounds familiar! (ca 2020)
OK, So... what did FDA actually say today?

They say if you do not have symptoms

and therefore don't really know where in your infection you are... if at all

and worry you were exposed

And you rapid test Neg... well, test again 2 days later and if Neg.. 2 days later still

Aug 1 7 tweets 3 min read
The Presidents COVID infection highlights 2 key issues

1) CDC must update their guidance. 5 day isolation is simply not right:

Test to exit is MUCH more science based

2) Paxlovid Rebound is real. We and others are working to understand it better


washingtonpost.com/health/2022/08… Writing in @washingtonpost (top tweet) @bylenasun documents scientists questioning CDCs “5 day isolation” guidance that, still, does not include a Neg rapid Test before exiting isolation

The President Rapid tests to know he’s no longer infectious

CDC guidance is outdated

Jul 17 7 tweets 2 min read
Agree. We should be trialing additional vaccine types!

1) Nasal vaccines that block transmission

2) Spike w/ NON-Spike protein vaccines… Unlike Antibodies, T-cells don’t care if it’s Spike or any other protein… they only see the pieces after the virus has been chopped up.

1/ We have put SO much effort into single protein mRNA vaccines. Great, bc they have worked really well in general.

But our immune system is Massively capable to recognize many proteins at once.

Anytime we get infected w a pathogen we see TONS of epitopes, not just on Spike

Jul 17 4 tweets 2 min read
On Monkeypox

When COVID first hit, officials kept saying "4 more weeks"

Experts understood "weeks" was ridiculous

Now we see same false narrative developing for Monkeypox

Officials - Lets not give public false expectations this time
MPX is not "weeks", but months - maybe yrs From the AP... stating that officials are warning that Monke That said, we have the upper hand w Monkeypox, if we act swiftly.

Already US Government is procuring vaccines and building up testing quickly. Yes, the vaccines are falling short at moment as demand outstrips supply. So they should be ramped... fast. USG is working on it

Jul 12 5 tweets 1 min read
Short 🧵

Comments like

"BA.5 is the MOST IMMUNE EVASIVE virus yet!"

Is massively misleading

It is not any more able to evade our baseline immune systems

"Immune evasive" is referring to how well it can evade the specific immune memory previously acquired from vax/inf

For example:

Scenario 1 - No preexisting immunity:
You've never seen a particular person before.
When they walk by you, you dont notice them

Scenario 2 - Preexisting immunity:
You do know the person and they walk by you, you recognize them

(Scenario 3/4 on next tweet)
Jul 12 12 tweets 3 min read
We're losing visibility of the virus

Being blind is a problem, esp approaching Fall again

For 1+ yrs, at eMed we've reported Positivity rates of ppl readying to travel

What we found recently is astounding –>

Suggests 1-2M new cases/day in US!
A 🧵

cnn.com/2022/07/11/hea… This number is 10x-20x othe fficial reported numbers!

Actually, our estimates prob represent lower bounds

So what are we measuring @eMedCertified to see this?

We've been looking at ppl readying to travel internationally who use eMed to verify home tests to get on flights

Jul 8 7 tweets 2 min read
On PCR Ct values

Physicians often warn against using PCR Ct values - often bc of variability in swabbing

However, what many forget is virus load is measured on a log scale

Even if a swab misses 90% of what another swab got… this amounts to a difference in only 3 Ct values

That’s right, If a swab only collects 10% of what another swab does, the difference in CT counts is minor - 3 Cts

In fact, if a swab is so badly performed that it only collects 1% of of another swab… it’s only a difference in 6 Cts…

Logarithmic growth is a great buffer

Jul 4 4 tweets 1 min read
Do Tests detect new Variants?



MOST mutations are in one part of the virus (Spike)

Most tests (esp rapid tests) detect other parts of the virus

It’s like someone getting plastic surgery mostly on their face, and then asking if their shoes still fit

Of course, yes! That said, there is an ongoing effort to continue to monitor for new mutations in new variants and ensure that no mutations are impacting the parts of the virus that different tests detect.

When something is identified, those particular tests are swiftly removed or updated
Jun 30 5 tweets 1 min read
Meetings/Schools/Work keep asking ppl to be boosted OR Test

No, why are we NOT learning!

Vaccination ≠ Test Neg

Obviously, vax'd ppl get infected & spread virus

If serious about keeping conferences safe

• Test each AM

Vax keeps YOU safe but doesn't stop transmission

If you have a conference with 1,000 people

And population prevalence of ppl being infectious is 2%

That's 20 Infectious people walking into the conference

Testing everyone in the AM will slash 20 the number of infectious people walking in to just 1 or 2 infectious people

Jun 26 11 tweets 3 min read
Is the monkeypox outbreak much bigger than reported?

Of course!

The number of infections already detected, despite major limitations in getting tested, means we count only the tip of the iceberg

Let’s not reinvent the mistakes of COVID & pretend we detect most cases

The good thing is, monkeypox testing is becoming accessible and encouraged much faster than it was for COVID

But lets not fool ourselves. At beginning of COVID, many epidemiologists thought we were detecting most cases

That was dreaming. we were catching a (small) fraction

Jun 23 6 tweets 3 min read
Important study of #rapidtests in children

~50% Pos children still Pos for days AFTER @CDCgov guidance says they can return (at 5 days)

Among those tested via virus culture, ALL culture Pos specimens were Rapid Ag Pos and Vice Versa

Test to Exit!


medrxiv.org/content/10.110… Importantly, numerous children were still #rapidtest Pos AND virus culture Pos as long as 14 days out!

Even though they had NO symptoms!

Symptoms often reflect how your body is doing with the virus...

Which is VERY different than whether you are infectious!

Jun 18 6 tweets 2 min read
w Breakthrough infections

Our immune system provides early warning


now start when or BEFORE infectivity begins

(vs PRE-symptomatic spread, common if no existing immunity)

If you feel symptoms, ASSUME INFECTIOUS - mask at minimum

If you test Neg, test 24 hrs later Almost all infections today are breakthroughs

So even if the virus hasn’t grown up enough to turn a test Pos at moment symptom start

with how infectious new variants are, it is important to consider symptoms as a first indicator of being infectious

Like we do w flu!

Jun 18 10 tweets 3 min read


Rapid Tests remain the best to answer this!

Rapid Tests are VERY Sensitive AND Specific for infectious virus

PCR is Sensitive but *NOT* Specific

(PCR creates many false Pos results when the question is "do I have infectious virus?")

1/ Image A CRITICAL aspect of this data...

Although Rapid Antigen Tests detected only 41% of PCR Pos people

(and only 12% if people were Asymptomatic)

They detected **96%** of all people with infectious virus!

(and 100% of Asymptomatic people with Infectious virus!!)

2/ Image