Thread by @deonandan

This thread will trigger a troll feeding frenzy. But I think it's necessary. It's time to summarize a timeline of COVID vaccine statistics and what they say about whether the vaccines reduced transmission or not, and whether "experts" lied or not. Here goes...

(Thread [1/17])

To begin, let's remember that vaccines seek to do 4 things, in descending order of importance and likelihood:
1. prevent death
2. prevent hospitalization
3. prevent symptomatic disease
4. prevent infection & transmission

[2/17]

2020: COVID mRNA vaccines shown in RCTs to be ~95% effective in preventing symptomatic disease caused by original Wuhan variant.


[3/17]nejm.org/doi/full/10.10…

To receive Emergency Use Authorization, vaccine did NOT need to stop transmission (though that would have been nice). Criterion was reduction in symptomatic disease by >50%, which was met and exceeded.
[4/17]
fda.gov/media/139638/d…

Even so, those original COVID vaccine formulations DID reduce transmission, as shown in multiple studies in early 2021.
[5/17]


reuters.com/article/uk-hea…
thelancet.com/journals/lanep…
thelancet.com/journals/lance…

Throughout 2021, evidence was mounting that COVID vaccines were indeed significantly curtailing transmission. Every sign pointed to the pandemic ending early if we could get enough people vaccinated quickly.
[6/17]
science.org/doi/10.1126/sc…

This was when some countries brought in vaccine passports, which made scientific sense. (You can debate the ethics elsewhere.) By slowing mixing of vaccinated & unvaccinated populations, risk of breakthrough infections was reduced.
[7/17]
cmaj.ca/content/194/16…

The emergence of Delta variant changed the math considerably. Two doses of vaccine were still ~70% effective at preventing Delta infection, which was pretty darned good! We could still tame the pandemic with vaccination if we did it fast enough...
[8/17]
ncbi.nlm.nih.gov/pmc/articles/P…

Then the emergence of Omicron (noticeably in Canada in late 2021) changed everything by curtailing vaccine efficacy. This is when vax passports stopped making sense, as they were disproportionately exposing vaxxed people to the virus, though they had diminished protection.
[9/17]

By 2022, it was clear that vaccination was no longer subduing transmission *significantly*. But 3 doses of gave substantial protection against death for both delta (80%) and omicron (78%), along with 61% protection against admission to hospital.

[10/17]
bmj.com/content/381/bm…

But beware the narrative of the vaccine minimizers. The original vaccine could STILL reduce Omicron transmission somewhat.
[11/17]
gavi.org/vaccineswork/n…

A telling California prison study in 2023 found that *one dose of any COVID vaccine* reduced the probability of an infected inmate transmitting infection to his cellmate by 24%. Again, that's reduced TRANSMISSION.
[12/17]
nature.com/articles/s4159…

The bivalent booster came out in Sep/2022. It was able to prevent actual infection by ~54%, which means it was also significantly slowing transmission. Yet uptake was poor.
[13/17]

jamanetwork.com/journals/jama/…
cdc.gov/mmwr/volumes/7…

The newest XBB1.5 booster came out in 2023. It has an efficacy against hospitalization of >70%
[14/17]

news-medical.net/news/20231217/…

Newest XBB1.5 booster also has an efficacy of ~54% against symptomatic infection. This is not as great as the 95% we saw in 2020, but it's pretty damned good! Yet currently only 16% of Canadians have received this vaccine.
[15/17]
cdc.gov/mmwr/volumes/7…

A robust meta-study of secondary attack rates throughout the pandemic found that all the vaccines offered some degree of reduction in TRANSMISSION, regardless of the variant:

[16/17]
jamanetwork.com/journals/jaman…

What's the takeaway?
1. COVID mRNA vaccines work.
2. They have always worked.
3. They work best when the vaccine is updated to match the current variant.
4. They have always reduced transmission.
5. They still reduce transmission.
6. Nobody lied to you.

[17/17]

Oops, those last 2 links are broken. Here are the proper ones:

thelancet.com/journals/lanep…
thelancet.com/journals/lance…