There was an extraordinary acceleration of football’s Covid crisis on Thursday as the Premier League postponed six fixtures in one day but resisted calls for a ‘firebreak’ suspension, insisting that play will go on. Manchester United and Leicester were joined by Watford, Norwich and Brentford in having too few players available to fulfil their weekend fixtures, with Leicester’s game at home to Tottenham on Thursday also called off. Only five matches remain in the weekend’s top-flight schedule, but with cases reported at Liverpool, Burnley and Chelsea further revisions cannot be ruled out. Brentford’s Thomas Frank said this weekend’s Premier League fixtures and next midweek’s Carabao Cup ties should be suspended to “break the chains” of infection. Organisers, meanwhile, doubled down on emergency regulations and a new focus on changing the minds of vaccine-refusing players. An explosion of cases at Manchester United caused their match against Brighton on Saturday to be called off. It is understood a combination of Covid and fitness issues had left only seven players from their first-team squad available for selection. Earlier a worsening picture at Leicester had forced their game against Tottenham to be postponed. Then shortly before 7pm GMT the league announced that four weekend fixtures would not go ahead: Southampton v Brentford, Watford v Crystal Palace, West Ham v Norwich and Everton v Leicester. The league said Brentford had closed their training ground and were unable to prepare and that Watford, Norwich and Leicester had insufficient players, with injuries and other illnesses contributing in Norwich’s case. On Wednesday Watford confirmed a rash of positive tests just a few hours before they had been due to step out at Burnley. The Premier League has come in for criticism over late decisions and a lack of clarity over its rules, but in announcing the United and Brighton postponement it insisted it was determined to play on. “While recognising a number of clubs are experiencing Covid-19 outbreaks, it is the league’s intention to continue its current fixture schedule where safely possible,” it said. “The health and wellbeing of all concerned remains our priority.” Some fixtures have continued despite Covid cases this week, including Chelsea’s home match against Everton and Norwich’s defeat by Aston Villa on Tuesday. With players now taking daily lateral flow tests, a new round of data will be available before this weekend, the crowded Christmas schedule coming up close behind. Frank told reporters on Thursday morning he thought all games should be called off. “We think we should postpone the full round of Premier League games this weekend,” the manager said. “Covid cases are going through the roof at all Premier League clubs; everyone is dealing with it and having problems. “To postpone this round and also the Carabao Cup round [next Tuesday and Wednesday] would give everyone a week at least, or four or five days to do everything at the training ground so everything is clean and you break the chain.” The Leeds United manager, Marcelo Bielsa, also expressed uncertainty over playing on, saying there were concerns over sporting integrity. “I would not like to come up against a team that is depleted due to Covid,” he said.“I would not like to take advantage of that.” Manchester United, Leicester and Watford have also shut their training grounds, with Leicester saying they had done so as “a circuit breaker to help reduce the risk of further infection”. On Thursday Brighton announced they would be limiting access, with training suspended over the weekend despite the United postponement. In the face of growing pressure the Premier League continued to stick by medical protocols, introduced a week ago, in the hope they will slow the spread. On Thursday the EFL detailed new regulations, which fall in line with those in the top flight, as it confirmed that fixtures in all three of its divisions had been postponed. New ‘red’ protocols will limit physical contact and time spent indoors at EFL training grounds. Players will for the first time also be expected to test themselves daily, using NHS lateral flow tests subject to availability. The EFL also spelled out its criteria for a match suspension, with clubs expected to play if they have 14 players and a goalkeeper available. The EFL also released figures about vaccination among its players as a quarter of players remain unvaccinated and are refusing to get a jab. This compares with 59% who are double-jabbed, with 19% either single-jabbed or willing to take the vaccine. The figures were released as concern among clubs over unvaccinated players has risen up the agenda, given the role they may play in spreading the virus. Before Liverpool’s match against Newcastle, Jürgen Klopp used his programme notes to reveal his Liverpool squad would soon be receiving their booster doses and called for others to get jabbed. “We have a very high take-up of the vaccine at our club and have done for a long time,” he wrote. “I have no issue telling you I received my booster jab as soon as I was eligible and again that will be the case for many if not nearly all within our ranks in the coming days and weeks … Ignore those who pretend to know. Ignore lies and misinformation. Listen to people who know best. If you do that, you end up wanting the vaccine and the booster.” Klopp confirmed before kick-off that three Liverpool players – Fabinho, Virgil van Dijk and Curtis Jones – were self-isolating after positive Covid-19 tests. The Chelsea manager, Thomas Tuchel, revealed that Romelu Lukaku, Timo Werner, Callum Hudson-Odoi and the injured Ben Chilwell have also tested positive.