Thread by @DrEricDing

⚠️’CANARY IN COALMINE’ mega outbreak. Many large public events in Massachusetts town in early July led to 469 #COVID19 cases➡️ 74% in **fully vaccinated**; 90% sampled #DeltaVariant. *Viral loads similar* in fully vaccinated vs unvaccinated. CDC worried.🧵
cdc.gov/mmwr/volumes/7…

2) What are the implications for public health practice?

➡️ “expanded prevention strategies, including **universal masking** in indoor public settings, particularly for large public gatherings with travelers from many areas with differing levels of #SARSCoV2 transmission.”

3) People were jam packed on Cape Cod— “Persons with COVID-19 reported attending densely packed indoor and outdoor events at venues that included bars, restaurants, guest houses, and rental homes.” ➡️ 14 days later… local cases went from *zero* to 177 per 100,000 !! ⚠️

4) This study was not yet published yesterday when the leaked CDC memo was released. But it was likely the impetus of the leak and the new CDC mask rules.

https://twitter.com/drericding/status/1420958565032943621

5) And by god… why the heck did it take a leaked memo for the CDC to recognize all this?!?!

https://twitter.com/DrEricDing/status/1420957777409740807

6) we have long known that fully vaccinated can still transmit if they get infected. Much less risk of infection of course but the risk is clearly non-zero as seen from the Cape Code mega outbreak now. But we have known this from Singapore from early to mid June.

https://twitter.com/drericding/status/1421049539495186435

7) Singapore Ministry of Health data on vaccinated breakthroughs and vaccinated transmission doesn’t lie.

https://twitter.com/DrEricDing/status/1421036382626193410

8) And we have known Singapore breakthrough onward transmission since definitely mid June. It was clear as night and day. And we also knew asymptomatic vaccinated also can transmit too.

https://twitter.com/DrEricDing/status/1421037975903907843

9) Here what really grinds my gears (makes me mad)… CDC’s internal leaked memo says “UNIVERSAL MASKING” needed. What did @CDCDirector recommend? Just indoors in high transmission areas. And “areas” is not well defined—states? Cities/countries? Universal best—Simple saves lives.

https://twitter.com/DrEricDing/status/1420959411166658560

10) If mega outbreak happened on just little Cape Cod, I don’t want to imagine this… Lollapalooza kicked off in Chicago. Organizers are expecting 110,000 people a day for 4-day music festival—biggest event since the city reopened. Not going to end well.

11) reminder — “while vaccine is good, it is not a bulletproof vest against you (vaxxed) getting infected, carrying the virus and you spreading it to others.” ➡️ though remember the risk of infection if vaxxed is much lower. But it’s non zero.

12) there is new data that breakthroughs are much milder and much shorter duration than infections of unvaccinated. That is great news. But again the viral load in the Cape Cod MA data shows it’s the same if infected. So it’s not a zero risk. But infection is shorter.