Thread by @HelenBranswell

1. Good morning. #ACIP is meeting today and tomorrow. Today, at least, I will be live tweeting.
@US_FDA has not yet indicated what it is going to do with Pfizer's application for a booster license. So it's really completely up in the air at this point how this turns out.

2. You'll recall FDA's advisory committee, #VRBPAC, voted that there wasn't enough data to approve the Pfizer application to give a booster to everyone 16 & older. VRBPAC did agree there was enough data to authorize boosters for people 65 & older & people at high risk.

3. But as I mentioned, FDA hasn't indicated what it's going to do. It is not bound to follow #VRBPAC's advice, but it will cause a real stir if it does not. If it doesn't follow VRBPAC's advice, it may set up a situation where a second advisory committee #ACIP disagrees with FDA.

4. So strange going into a 2-day meeting where #ACIP has no clue what it's going to be asked to do.
In theory there will be a vote tomorrow. But if FDA doesn't make its ruling, there will be no vote.

5. Pfizer senior VP Bill Gruber is now starting to present the company's data on the booster. This will be a rehash, I think, of the presentation Gruber presented at #VRBPAC on Friday.
If you want to listen to #ACIP, you can listen here: video.ibm.com/channel/VWBXKB…

6. Pfizer VP Gruber presented data on side effects after dose 3. In the main, the rates of side effects after dose 3 (dark blue) were lower than after dose 2 (light blue). There was more lymphadenopathy — swollen lymph nodes. #ACIP

7. Is dose 3 of the Pfizer vaccine going to lead to dose 4? Pfizer VP Gruber said it's the company's expectation and hope that the response to dose 3 will be longer lasting than the response to doses 1 and 2. #ACIP

8. Adding this here because @doritmi is helping me with the live tweeting! Just as FDA isn't bound to accept #VRBPAC's advice, @CDCDirector isn't bound to accept #ACIP's recommendations.
If 2 expert advisory groups are overruled on boosters, it will be *interesting*.

9. Pfizer VP Gruber was asked if the company is studying use of a Pfizer booster by people who earlier got Moderna or J&J vaccines. Gruber said the company isn't, but welcomes the work done by #NIH & in the UK. #ACIP

10. @DocJeffD asked whether Pfizer is looking at changing the interval between doses 1 & 2; longer intervals generally lead to a more long-lasting response. Gruber said the company is interested in exploring options; this might work after the acute phase of the pandemic.

11. Up now: @CDCgov's Natalie Thornburg is presenting on "Immunity and SARS-CoV-2" — what's known about the immune response to the virus that causes #Covid (and I'm guessing the response to SARS-2 vaccines).
Early take away: It ain't all about antibodies.
#ACIP

12. Immunity isn't binary, says Thornburg, especially when you're talking about a respiratory infection.
What she's describing is more like a light dimmer than an on-off switch. #ACIP

13. #ACIP member Sarah Long says antibodies will always wane & studies in macaques suggest that only with really high levels of antibodies will upper airway infections be prevented. So sterilizing immunity with these vaccines aren't likely possible.

14. One of #ACIP's non-voting affiliates asks if Pfizer has any data on the risk of anaphylaxis after the 3rd dose. Pfizer's Gruber says they don't have data but will need to monitor for it.

15. #ACIP member Keipp Talbot reiterates that #Covid vaccines probably won't be able to prevent all disease.
I suspect that's a "we can't boost our way back to a permanent 95% VE" comment.
Committee adjourns for a 10 minute lunch break.

16. #ACIP is now hearing a presentation on the vaccine efficacy data being gathered in the U.S. Progressive waning seen for both Pfizer and Moderna over time. But with the 1 dose J&J vaccine, VE actually rose during the study period.

17. US data shows that fully vaccinated people who were hospitalized with #Covid were typically older & more medically fragile than unvaccinated people who were hospitalized with Covid. They were also more likely to live in long-term care. #ACIP

18. It's interesting trying to eat lunch (soup) and Tweet #ACIP.

19. For the mRNA vaccines, "we saw a large decline" against all infections, less so for hospitalizations & severe disease. #ACIP

20. Data now being presented from the SUPERNOVA Network. Great name.

21. This is an interesting slide. The VE of the mRNA vaccines against hospitalizations isn't really a lot lower among people with comorbidities than among people without. #ACIP

22. The summary slide for the #ACIP presentation on US vaccine efficacy data.

23. #ACIP member Sarah Long urges her fellow panel members to delink in their minds VE against all infections from VE against hospitalizations. Preventing the former will not be possible except for during a short period after a dose, she said.

24. #ACIP hears that in Israel, the definition of severe disease among breakthrough cases includes some treated on an outpatient basis, based on respiratory symptoms. That's not part of the US definition of severe disease — needs to be kept in mind in considering Israeli data.

25. #ACIP is now hearing about modeling work trying to assess the affect of booster doses in nursing home residents. This, obviously, is a population about which there is huge concern.
Hard to see that boosters wouldn't be recommended for this vulnerable population.

26. Even with highly effective boosters, if there's a lot of #Covid in the community & a lot of introduction into nursing homes by unvaccinated staff, boosters won't stop cases in nursing homes, #ACIP is told. Higher vax rates among staff would have a greater impact.

27. #ACIP breaks till 2 pm ET. Rest of the day is about #Covid vaccine safety, including an update on vaccine safety in pregnant persons.

28. #ACIP is back! Hearing an update on monitoring for adverse events following #Covid vaccination, from Dr. Hause (pronounced House!). She has data for people who reported getting a 3rd dose of mRNA vaccine. (n=21,935) Interesting who is getting themselves 3rd doses.

29. Among people who got a 3rd dose of mRNA, side effects were comparable to dose 2, but were reported at slightly lower rates. #ACIP

30. #ACIP member Keipp Talbot is presenting on the safety data from Israel following 3rd dose receipt. She noted that the substantial reduction after the 3rd dose is at least partially due to the length of followup (ie it hasn't been long enough yet).

31. #ACIP chair Grace Lee just declared a 1-minute break.
Long days with few breaks are hallmarks of ACIP meetings. But a 1-minute break has gotta be an ACIP record.

32. @CDCgov's Sara Oliver, known for tour de force presentations, is now reporting to #ACIP on the Covid vaccine work group's take on the data so far. Typically the work group tells the larger committee: "We think we should land the plane here." And ACIP typically agrees.

33. A couple of #ACIP members have raised questions about whether the committee could recommend boosting with Pfizer for people who received one of the other vaccines. Moderna and J&J are not as far along in seeking authorization for boosters.
(No answers forthcoming yet.)

34. #ACIP member Talbot said the reason for vaccinating health workers would be about trying to ensure they only have mild illness if they contract Covid, to try to minimize the impact on the workforce. With the surge of Delta cases, hospitals find themselves with too few staff.

35. #ACIP member Beth Bell makes an important point: The committee should keep in mind it is making recommendations for *now.* Data are currently sparse but more data will come and recommendations may then change.

36. @US_FDA's Doran Fink says the agency's position on boosting with a different vaccine (ie Pfizer after Moderna) is that there are no data to inform that decision. He said he needs to check with FDA leadership on legal questions related to using a Pfizer boost after another vax

37. Molly Howell, the non-voting rep for the Association of Immunization Managers suggests this is going to be a real challenge in long-term care facilities, where residents may have gotten Pfizer or Moderna. Questions how workable it will be to do Pfizer now, Moderna later.

38. @US_FDA still hasn't indicated what it's going to rule on Pfizer's booster application, so much remains in the air. But it seems preeeeeeeeety clear that the rollout of a booster shot program is gonna be messy as hell.

39. And now #ACIP is shifting to a discussion of Covid vaccination while pregnant. Most of the pregnant people who took part in V-safe, the CDC's safety monitoring program, got one of the mRNA vaccines.

40. Analysis of data suggests that receipt of an mRNA vaccine is not associated with a higher risk of having a miscarriage. (Spontaneous abortion or SAB in this slide.)

41. More than 123K pregnant people have been diagnosed with #Covid in the US. It's likely an underestimate. A lot of the cases are among unvaccinated people. #ACIP

42. ICU admissions and deaths among pregnant people have increased recently, #ACIP is told. In fact, more pregnant people died from Covid in Aug. than in any other month in the pandemic.

43. Despite the evident risks associated with contracting Covid during pregnancy and the evident safety of the vaccines for pregnant people, the rate of vaccine uptake among pregnant people is only about 30%. #ACIP

44. And #ACIP concludes for today.

45. If @US_FDA issues an EUA for the Pfizer booster by noon tomorrow, #ACIP will reconvene tomorrow to make recommendations on how the booster should be used.
If there is no recommendation, the meeting will be rescheduled.
THE SUSPENSE IS KILLING ME.

What she said.
Can someone please explain to me why 5 full days have passed since the #VRBPAC vote and @US_FDA still hasn't revealed how it's going to handle the Pfizer booster EUA?