Haven't seen or heard that about P1 (Gamma) so until I see some concrete evidence I'll stick to what I said.
After initially containing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), many European and Asian countries had a resurgence of COVID-19 consistent with a large proportion of the population remaining susceptible to the virus after the first epidemic wave.1 By contrast, in Manaus...
www.thelancet.com
Reinfection by the severe acute respiratory syndrome coronavirus type 2 (SARS-COV-2) has been reported in many countries, suggesting that the virus may continue to circulate among humans despite the possibility of local herd immunity due to massive previous infections. The emergence of variants...
pubmed.ncbi.nlm.nih.gov
That's two different studies across two different cities, where despite 70% infection rates in these cities, P1 (aka Gamma) came around and reinfected everyone, leading to a hospital crisis. Its happened
TWICE now, at least. It will happen again. The earlier "reinfection" was in Manaus, the 2nd case of this happening was Araraquara City.
In contrast, the vaccines have been shown to be effective against P.1. See here:
https://www.medrxiv.org/content/10.1101/2021.06.28.21259420v2
The data with Delta is somewhere inbetween what everyone is saying, some that's been vaccinated already caught it too, some haven't.
Citation? The CDC has only said that Delta has high viral load (aka: the virus is in your body and you're spreading the disease around). But vaccinated people infected with Delta do not get symptoms, get sick, go to the hospital, or die (roughly 98% of the time. The remaining 2%... well... no vaccine is perfect but 98% protection is pretty damn good). The vaccine only helps your immune system prepare, if you've got cancer and/or HIV (or other immunocompromised), you're not going to fare well, even with the vaccine.
Preventing the vast majority of healthy people (well... healthy by American standards. Our diabetic + obese population) from going to the hospital when we get COVID19 is a big help however. Cutting down on 90%+ of hospitalizations and 98% of deaths will help out in this upcoming surge.
---------
Case in point. We know where the virus is affecting us in the USA.
Screenshot of CDC's current COVID19 tracker map:
https://covid.cdc.gov/covid-data-tracker/#datatracker-home
Look at all those locations getting infected. Also check out their vaccination rates. The areas with low vaccination rates are getting sick. Its that simple. Sure, my state is still getting some cases, but compared to other states? The map alone proves it. We know the vaccine works from this data alone.
Delta is over 90% of the cases here in the USA. So the map above directly demonstrates how effective the vaccinated regions are doing vs Delta, compared to the unvaccinated regions.
EDIT: I probably should also post the vaccination map, shouldn't I?
There ya go. Vaccinations prevent Delta. Period. The more vaccine you have (lower map), the less Delta you get (upper map).