2/ Fundamentally, there are two parts to the equation—
Am I protected?
And am I at high risk of transmitting to those who are not?
As vaccine effectiveness wanes against infections in all age groups, those of us who have a lot of exposure to the virus & to vulnerable folks…
3/ are going to increasingly be at higher risk of transmitting onwards.
As a doctor taking care of immunocompromised patients in whom vaccines don’t work as well— reducing the chance of getting infected becomes more important. This holds true for those with…
4/ vulnerable folks at home as well. As we have seen, this epidemic has been about protecting ourselves AND those around us.
I think it’s important to remember that boosters are one way of doing this (there are others that respect global equity more if we can ship the doses)
1/ Really a privilege to hear from Dr. Steve Luby @StanfordCIGH discuss the now well-known Bangladesh masks randomized trial for #covid19
One of the most important take-aways for me is that masking actually increased physical distancing, not the opposite.
Why does this matter?
2/ As you may remember from earlier last year, one of the reasons that the US public health agencies said that community masking would be harmful is that it could decrease physical distancing & increase transmission.
This hypothesis was used to support early policy against masks
3/ Many of us pushed back saying that this “risk compensation” logic wasn’t necessarily true— that masking could instead serve as a reminder that we were in a pandemic.
And that it could increase distancing + provide personal protection + source control
🧵🧵 1/ While two-dose vaccine series have been shown to remain exceptionally protective against #covid19 disease, especially in younger age cohorts — we know that vaccine effectiveness against #SARSCoV2 infection has decreased.
Booster doses can help reduce onward transmission.
2/ As I think about this more, this is especially important for the many immunocompromised patients that we are treating as healthcare providers.
These are patients in whom vaccines don’t work quite as well to induce an immune response.
3/ Similarly, reducing transmission to children is an important goal, even if it deserves examination of many trade-offs.
The best way as of now to protect kids is to minimize risk of transmission from adults. Vaccines are one part of that equation.
1/ It's difficult to study #SARSCoV2 transmission in the real world bc of many confounders
In our study of hospital roommates, we studied this in a relatively controlled setting
We found that the virus transmits efficiently beyond 6 feet & despite a curtain in between roommates
2/ We were examining a number of cases that turned positive but whose initial tests were negative (so early incubation period) so they were roomed with other patients in shared rooms
This allowed us to explore a window into exposure when index cases are most infectious
3/ We found that for those with cycle threshold values <=21 (meaning high viral load), 11/18 transmitted to their roommate (61%)
Roommates are 7 feet apart (head to head in bed) with a solid curtain in between
If transmission was primarily droplets, we wouldn't expect this
A few things on my mind
🧵🧵 1)
-#SARSCoV2 is spread by aerosols at short and long range— not sure why there is still debate about this. Seeing tweets from Canada that this is still up in the air- no pun intended cc @DFisman@kprather88@linseymarr
2)
-global vaccine equity is an afterthought for rich countries; this is exactly how we thought this would go— for pharma, it’s about $$ & always was. Charity won’t solve this issue. It’s a structural problem cc @ThomasPogge@amymaxmen@RanuDhillon@rajpanjabi
3)
Boosting fully vaccinated folks w/ mild co-morbidities won’t stop the epidemic here — fully vaxx’d transmitting much less