You shouldn't take much comfort in that. Delta plus was just identified in India in April, and has already made it to nine countries. The standard Delta was discovered last year.
https://www.bbc.com/news/world-asia-india-57564560

They won't know how fast it is spreading for some time. In fact, as you know, they just recently determined that the standard Delta was spreading faster than they expected, and so Britain had to delay coming out of lockdown for another month so that more people could get vaccinated. And that is with a variant they have known about for some time.

Just look at the characteristics of Delta plus, and see how it looks.

EDIT: Here is a slightly more complete account.
https://www.theguardian.com/world/2021/jun/03...it-exist-should-concerned

CVnCoV is produced by Curevac.

"2021 Status: 47% Interim Efficacy—CureVac acknowledged June 16 that CVnCoV showed an interim vaccine efficacy of 47% against COVID-19 disease of any severity and did not meet prespecified statistical success criteria in the pivotal Phase IIb/III HERALD trial (NCT04652102; EudraCT Number: 2020-003998-22) in approximatively 40,000 participants. HERALD was conducted in 10 countries with a combined 29 COVID-19 variant strains. At least 13 variants were circulating within the study population subset assessed at the interim analysis.

“While we were hoping for a stronger interim outcome, we recognize that demonstrating high efficacy in this unprecedented broad diversity of variants is challenging,” said CureVac CEO Franz-Werner Haas, LLD, LLM."

Those results caused a 41% drop in the company's share price. Ouch!

https://www.genengnews.com/covid-19-candidates/curevac/

Mixing Covid vaccines gives good protection, study suggests

The Com-Cov trial looked at the efficacy of either two doses of Pfizer, two of AstraZeneca, or one of them followed by the other. All combinations worked well, priming the immune system. This knowledge could offer flexibility for vaccine rollout, say experts.

The trial results also hint that people who have already received two doses of AstraZeneca vaccine could have a stronger immune response if they were given a different jab as a booster if recommended in the [British] autumn.


More at: https://www.bbc.com/news/health-57636356

Effectiveness of COVID-19 vaccines against hospital admission with the Delta (B.1.617.2) variant.
According to this paper both AstraZeneca and Pfizer/BioNtech vaccines are still highly efficient against hospitalization for the Alpha *and* Delta mutation (see page 2). Unfortunately, it was not yet possible to determine vaccine effectiveness against severe disease.

Long-term changes to blood cells triggered by Covid-19 infection
https://www.fau.eu/2021/06/21/news/research/l...ed-by-covid-19-infection/

Excerpt:
"Their findings showed that the size and malleability of red blood cells varied considerably more in those suffering from the disease than in the healthy volunteers. This indicates that the disease damages blood cells and may explain the increased risk of blood vessel congestion and blood clots in the lung. It may also explain why oxygen supply is impaired in those who have contracted the virus, as this is one of the main tasks carried out by erythrocytes."