Number 10 spokesman said: "The police have made clear they are taking no action against Mr Cummings over his self-isolation and that going to Durham did not breach the regulations".
On Wednesdays Mr Johnson would ordinarily face Labour leader Sir Keir Starmer at Prime Minister's Questions, but MPs are now on recess.
Mr Johnson had hoped the issue had calmed after he addressed the Liaison Committee yesterday, made up of some of Parliament's most senior MPs, suggesting repeatedly it was time to "move on" from the affair.
On Wednesday several MPs directly challenged the prime minister as he again voiced his support for the aide, who is credited with delivering a big majority for Mr Johnson at a parliamentary election in December.
Mr Johnson also admitted it had been a "very frustrating episode", which he sought to dismiss as a "political ding dong" with inaccuracies but he refused to state which aspects of the allegations were untrue.
In an indication of the difficulties Mr Cummings' actions are causing at the top of Government, ministers were forced to deny that a review was being launched into fines issued to other people travelling with their families.
More female representation at the daily Downing Street press conferences would have been desirable, Boris Johnson has admitted.
Ahead of the Prime Minister's appearance, Liaison Committee chairman Sir Bernard Jenkin told the PA news agency: "I have got no intention of preventing any subject any member of the committee wants to raise".
In a statement, Durham Police said that no further action would be taken against Mr Cummings, according to The Telegraph.
Women and Equalities Committee chairwoman Caroline Nokes, who will also be on the panel, has said "there can not be one rule for most of us and wriggle room for others".
Mr Cummings' decision in March to drive from his London home to his parents' farm in County Durham with his wife - who had coronavirus symptoms - and his son has dominated the headlines since the story broke on Friday night.
The prime minister used the phrase "move on" five times in 20 minutes, as he faced hostile questions from select committee chairs.
On Tuesday, Douglas Ross quit as a junior Scotland Office minister, saying he could not "in good faith" defend Mr Cummings' actions.
US Stocks surge with economic hopes
In Europe, Germany's DAX returned 1.3% and France's CAC 40 rose 1.8% after the announcement of the region's recovery fund. The Dow racked up its second straight 500-point gain , surging 2.2% to close above 25,000 for the first time since March.
Renault-Nissan-Mitsubishi plan to deepen cooperation
As CarAdvice points out, the next-gen Triton is about three years away, while the new Navara is around five years into the future. Global vehicle sales for Nissan were 43% lower than in March 2019 and down 47% for Renault and Mitsubishi .