Thread by @ASlavitt

COVID Update: An internal document from CDC shows Delta is a whole “new war.”

First real estimates of spread & breakthrough cases. And a clear sense of why CDC policies are changing.

More here soon. 1/

Point 1: Vaccines work. They dramatically reduce the risk of cases (8x) & even more so serious cases (25x). But they don’t work perfectly.

With 165 million fully vaccinated people, they estimate 7,000 breakthroughs/day. 2/

A thorough discussion of breakthrough cases & vaccine efficacy is here in this discussion with what Pfizer sees in the data. Worth listening to to understand. 3/

https://twitter.com/inthebubblepod/status/1420718316251926529

Point 2: Delta vaccine effectiveness is reduced vs. Alpha. This could be because of waning effectiveness or the increased viral load or both.

Thankfully hospitalizations are only minimally impacted. 4/

With only slight movements in hospitalization risk, with more and more people vaccinated, the percentage of people who are hospitalized with COVID who are fully vaccinated will climb. In some studies it is approaching 10%. That is to be expected. Absolute numbers are key. 5/

Point 3: The document calls out who is most at risk and points to some data showing the risks are higher among the elderly & among immunocompromised people.

In nursing homes:

Protection against infection looks like 65-75%. Hospitalization 85%. 6/

Point 4: They have compared Delta to other infectious diseases including 2020 COVID.

Delta spreads as fast as chicken pox (but is more lethal). The 2020 version was significantly less transmissible (more like SARS or Ebola—but far less deadly).

Delta is a new disease. 7/

Point 5: Delta has much higher viral loads & potentially sheds longer. If so this could mean longer isolation periods. 8/

Point 6: Reinfection risk may be higher if infection occurred more than 6 months ago. Strikes a blow against herd immunity theorists who tell people to get infected. 9/

Point 7: Breakthrough cases of Delta appear as transmissible as those of unvaccinated people.

Another blow against blanket immunity if future variants look like this one.

10/

Let me tick through some implications. 11/

IMPLICATION 1: The vaccine is our best tool. It’s efficacy is lower but it has a dramatic & lifesaving impact.

If vaccination rates don’t increase meaningfully, COVID waves will likely continue. 12/

IMPLICATION 2: Around only vaccinated people you are safer but not perfectly safe. Vaccinated people could shed the virus to the same degree as unvaccinated people if they’re infected & pre-symptomatic.

Also, if you’re sick, you gotta stay home. 13/

IMPLICATION 3: We will need to shore up nursing home safety with preventative measures until a booster is approved. 14/

IMPLICATION 4: Employers should follow the lead of the federal government & require vaccines or a negative test result 2x week.

In some job types where there is a lot of public interaction, like health care settings, vaccines should be required. 15/

IMPLICATION 5: Points 6 & 7 would make herd or blanket immunity more elusive. It would require almost full vaccination levels. 16/

IMPLICATION 6: Unlike 2020, given the vaccines, death rates will be dramatically lower. Lots of cases, fewer deaths.

But, while Delta is out there, expect deaths to climb some on an absolute basis for the low point they have been at. 17/

We don’t know how long Delta lasts— some data suggests we will see peaks soon & big declines. But that’s not certain. In the meantime, more caution is warranted than before. 18/

Seeing that before the school year begins would be very encouraging as would progress in vaccinations for under 12, boosters, anti-virals & additional tools in our arsenal.

Much more info on these areas on the podcast @inthebubblepod with Bourla & Topol. /end