1/ Pfizer says that a 3rd dose of its vaccine can boost protection against the Beta & Delta variants
BUT
does everyone need that boost?
2/ Do severely immunosuppressed people need extra doses of COVID vaccine? Certainly.
3/ Do older people (esp over 80) need extra doses of COVID vaccine? Probably.
4/ Does everyone else need extra doses of COVID vaccine? Possibly, maybe. That remains to be seen.

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Keep Current with Céline Gounder, MD, ScM, FIDSA

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More from @celinegounder

29 Jul
1/ This latest paper by @KizzyPhD, who helped develop @moderna_tx's mRNA COVID vaccine, helps us understand why vaccines can protect against severe disease in the lungs but not mild infection in the nose and throat.
science.sciencemag.org/content/early/…
2/ Lower antibody levels are needed for reduction of viral replication in the lower airway than in the upper airway.

RNA in BAL = amount of virus in the lungs drops more quickly than
RNA nasal swabs (NS) = amount of virus in the upper airway Image
3/ Antibodies taken from unvaccinated & vaccinated non-human primates (NHPs) were infused into hamsters.

Hamsters that were given antibodies from NHP who received the higher dose vaccine had little/no weight loss (i.e. little/no disease). Image
Read 5 tweets
28 Jul
1/ Today, Pfizer released a PRE-PRINT with 6 months of follow-up data for its phase 2/3 COVID vaccine trial:
medrxiv.org/content/10.110…

THE TAKEAWAY: 2 doses of the Pfizer vaccine are highly effective in preventing severe disease, hospitalization, & death out to 6 months. Image
2/ Pfizer saw no new safety issues between its 2-month and 6-month analyses.

This is consistent with what we've seen with every other vaccine. If people are going to have a side-effect from a vaccine, they'll have it within 2 months of getting vaccinated.
3/ The Pfizer vaccine was over highly effective in preventing ANY SYMPTOMATIC INFECTION out to 6 months:
2 months 96%
2-4 months 90%
4-6 months 84%
Read 4 tweets
27 Jul
1/ How is it possible that vaccines could prevent severe disease, hospitalizations, & deaths from COVID

BUT not prevent mild infections & onward transmission?

advances.sciencemag.org/content/7/12/e…
2/ If the vaccines induce systemic immunity protecting the lungs

but not mucosal immunity in the upper airway (nose, throat),

you could still get upper airway SARS-CoV-2 infection, causing no or mild symptoms

without severe illness (e.g. hypoxia or low oxygen levels).
3/ We're already seeing the benefit of mixing-matching different types of vaccines (what we call heterologous prime-boost).

Perhaps we should be doing the same with injectable COVID vaccines and intranasal COVID vaccines.
Read 4 tweets
27 Jul
1/ Clearing up confusion about what it means that Delta viral loads are ~1000x higher than the viral loads seen with the original SARS-CoV-2.
medpagetoday.com/special-report…
2/ We need to be precise in speaking about infectiousness.
Exposure = Dose x Time
If viral loads in infected people are ~1000x higher with Delta than original SARS-CoV-2, the dose of virus to which the uninfected person is exposed has gone up ~1000x.
3/ Exposure = Dose x Time
If Dose increases 1000x
the Exposure you would have gotten from an infected person early in the pandemic over 15 minutes
you now get in 0.9 seconds (~1 second).
15 minutes = 900 seconds
But in NEITHER scenario are you 100% sure to be infected.
Read 7 tweets
22 Jul
2/ COVID VACCINES WORK. They protect you from severe disease, hospitalization, and death.

IF YOU HAVEN'T YET GOTTEN VACCINATED, THIS IS THE TIME. Image
3/ The Delta variant has turned suburban streets into a @NASCAR track.

Seatbelts might be enough to keep you safe when you're driving in your suburban neighborhood, but if you're a NASCAR driver, you also want a helmet, airbags, and more. Image
Read 7 tweets
20 Jul
1/ Here is a comprehensive review of the data on whether we need COVID BOOSTER SHOTS.

THE MOST IMPORTANT TAKEAWAY:
IF YOU HAVEN'T YET GOTTEN A COVID VACCINE, NOW'S THE TIME!

I'll put a Threadreader unroll at the end for those of you who find that more convenient to read/share.
2/ Will we need COVID vaccine boosters?

Firstly, is “booster” even the right terminology?
I would argue not.

I think what we’re talking about is refining the COVID vaccine dosing regimen.
3/ When your doctor prescribes you medication for high blood pressure & then increases the dose, it doesn’t mean that the medication doesn’t work.

It’s that they didn’t know what dose would work for you or wanted to start lower rather than overshoot.
Read 148 tweets

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