I think the government has just produced a 21st century metaphor to replace "shutting the stable door after the horse has bolted" - after all, we don't deal with horses much these days:
Covid certificates to be compulsory for crowded venues in England
Covid certificates will be made compulsory for crowded venues such as nightclubs
from the end of September in a bid to boost vaccine uptake among young people, the vaccines minister, Nadhim Zahawi, has announced.
The government had previously backed away from the compulsory use of coronavirus certificates which involve customers using the NHS app to show their vaccination status, or prove they have had a negative test result.
Instead, the government had urged venues such as clubs and sports stadiums to introduce them as a matter of social responsibility.
But after footage emerged of packed clubs on Monday as the government allowed them to reopen, ministers plan to work with venues over the summer to encourage them to use the system and expects to make it mandatory from the autumn.
https://www.theguardian.com/world/2021/jul/19/covid-certificates-to-be-compulsory-for-crowded-venues-in-england
But until then, it's the Summer of Covid. They could have said this when they opened up vaccines for everyone, a month ago. If they did it in combination with giving the 2nd Pfizer dose 3 to 4 weeks after the first (as still recommended by Pfizer), they'd even have some people able to use nightclubs now (above 25s already, and even some 18 year olds within a week or so), if they'd had enough Pfizer vaccine. But no, their sacred dates came before the data, and they didn't dare ask people to take a free vaccine to stop infections and preserve the Right to Party.