Thread by @profshanecrotty

CDC Director Dr. Walensky made the right decision last night on boosters. 🧵
Boosters now available (not required) for Pfizer vaxxed after 6 months:
🔵  65 and older
🔵  healthcare workers
🔵  nursing home residents
🔵  50 and older with health problems
apnews.com/article/corona…

This was in line with the FDA decision last week. It also matches my suggestions two weeks ago on TWIV and VOSD. And earlier on UCSF Grand Rounds. It makes sense to have vaccine boosters available to these people, who received the Pfizer vaccine.

Again, the Pfizer vaccine booster shot is *available*. It is not *required* to count as fully vaxxed. That is because without the booster shot, the vaccine is still doing an outstanding job at preventing serious COVID-19.

The booster shot will prevent most *cases* of coronavirus infection (mild infections), and will probably generate more durable protection and immune memory.

Here are graphs of coronavirus infections and hospitalizations from Kaiser, with my vaccine comments above.
Pfizer vaccine efficacy against detectable infections probably wanes from ~90% to ~50% after 6 months, in the Delta era.

For people 65 and older who got the Pfizer vaccine, I think it is wise to get the 3rd dose (booster). It is a "better safe than sorry" approach, preventing cases of infection and potentially preventing hospitalizations over the next year. Balancing what we current know…

, which includes the persistent intensity of the Delta variant epidemic in America, and the coming winter season.

For healthcare workers who got the Pfizer, I think it is wise to get the 3rd dose (booster) to prevent cases and lost work time. Given that a PCR+ test results in a requirement to not go to work many places—even as an asymptomatic infection—it is helpful to get the 3rd dose…

preventing those asymptomatic and mild infections and transmissions.

Of those four groups of people, I think boosters are most highly recommended for nursing home residents, given that those have been sites of the worst outbreaks and there has been evidence of waning protection in that setting in the US.

It is quite reasonable that the FDA and the CDC did not recommend Pfizer booster shots more widely, because (1) the benefit is less clear in younger adults (and 16-17 y olds), and (2) the safety data provided to the FDA was limited. We hold vaccines up to a high safety standard.

It is appropriate to require reactogenicity (side effect) data in more than ~250 people (As I noted on UCSF Grands Rounds).

My understanding is data for over 1,000 people has been formally collected in Israel, and side effects were the same as the 2nd shot—plus over 3 million Israelis have received a 3rd shot-- so I have no safety concerns about the Pfizer 3rd dose,

but I would still want to see a larger formal data set for broader approval of a booster.

I appreciate this: "For most people, if you’re not in a group recommended for a booster, “it’s really because we think you’re well-protected,” said Dr. Matthew Daley of Kaiser Permanente Colorado."

It is plausible that the continuing protection by the Pfizer vaccine against COVID-19 hospitalizations is due to good durable T cell and B cell memory to the RNA vaccines. Discussed here

https://twitter.com/profshanecrotty/status/1437795168195948547

and here

https://twitter.com/rishirajgoel/status/1430148915064676352?s=20

This Pfizer booster policy does NOT immediately apply to people who got Moderna or J&J vaccine. Moderna is in the process of making a similar request to the FDA and CDC in the coming weeks. And J&J is in the process of making a similar request for a 2nd shot of their vaccine.

There is some evidence that protective immunity from the Moderna vaccine is more durable than the Pfizer vaccine. It is worth considering each vaccine independently and assessing the data.

As always, the biggest problem in America is the large number of unvaccinated adults. Any dose of vaccine that can be gotten to an unvaccinated American is FAR MORE valuable than a dose of vaccine to an already vaccinated American.

There are 53 MILLION unvaccinated Americans eligible for COVID vaccines. With almost 2,000 Americans dying every day from COVID, and almost every one of them unvaccinated.