Unvaccinated adults will be barred from large sports venues in England if the coronavirus pandemic places unsustainable pressure on the NHS over the winter.
The Government set out its plan for the months ahead on Tuesday, which includes 'Plan B' measures in the event of the pandemic significantly worsening.
These include the introduction of vaccine-only certification for any venue with more than 10,000 attendees, and for crowded indoor venues with over 500 attendees.
Vaccine-only certification would mean proof of a recent negative lateral flow test would no longer suffice.
The Government has said it will not introduce mandatory certification from the end of this month, as had been indicated earlier in the summer once all over-18s had been offered the opportunity to be double-jabbed.
However, it is encouraging the voluntary use of the NHS Covid Pass and it reserves the right to make certification mandatory should the situation worsen.
Certification was trialled during the Government's Events Research Programme (ERP) over the spring and summer, which included England matches at Euro 2020, Wimbledon and the British Grand Prix.
The Government's Covid Response: Autumn and Winter Plan document states: "Public Health England analysis of the Events Research Programme found that, while proof of full vaccination or a negative LFD test would not completely eliminate the possibility of an infectious individual attending an event, it should reduce the likelihood of someone transmitting highly infectious amounts of virus to a large number of individuals attending the event.
"The study concluded that promoting attendance by fully-vaccinated individuals at events will be important to mitigate risks.
"For venues, certification could allow settings that have experienced long periods of closure to remain open, compared to more stringent measures which may severely reduce capacity or cause them to close entirely."
Premier League clubs have been conducting certification spot-checks since the start of the season, as part of what it sees as prudent planning to ensure full capacities can continue in the event of restrictions tightening.
Chelsea said on July 28 that proof of double vaccination or a recent negative test would be needed to gain entry to home men's and women's matches this campaign.
EFL guidelines released on the eve of the current season encouraged individuals who were not double vaccinated to take a lateral flow test before attending a match.
The Government said it would give businesses at least one week's notice before mandatory certification came into force.
