The number of new cases barely rose last week for the first time since the second wave of the pandemic began in September.
There were 84,000 new cases of the infection last week, up from 78,000 the previous week.
Officials said it was too early to predict a peak and suggested that school closures could have slowed the rise in cases.
Sir Liam Donaldson, the Chief Medical Officer, said: “This could be a half-term effect and we cannot be completely sure.
“We have got to wait for another week or two to see what happens.”
The main fall in cases was seen among children aged between five and 15.
They have been disproportionately hit by the pandemic which has caused outbreaks in schools across the country.
But only children with underlying illnesses are part of the Government’s priority groups, who will be the first to receive the vaccine, although ministers have insisted that they have enough jabs to inoculate every person in the country if necessary.
Andrew Lansley, the Shadow Health Secretary, called on the Government to commit to vaccinating all schoolchildren in the country, as well as university students.
He said: "A school-based programme needs preparation and needs to be co-ordinated with vaccine availability.
“I urge the Government to make the decision and put the plan in place".
Sir Liam said that the decision on vaccinating children was complex, not least because the numbers involved could mean vaccinating pupils as the flu season was ending.
“We would hope to take a decision on this in the next few weeks," he said. "We are looking very hard at what might be the next steps.”
America has decided to include healthy children as part of the first groups to receive the vaccine, but here officials chose to concentrate on at risk groups more likely to develop complications.
However, a committee of scientists advising the Department of Health is expected to recommend that the vaccination of 10 to 18-year-olds starts before the end of the year.
The current priority groups include pregnant women, those with serious underlying health conditions and front line NHS staff.
The Government hopes to have inoculated 11 million people by the end of the first round of vaccinations in the middle of December.
Sir Liam also warned he was still concerned about the number of cases in intensive care which he said had “snowballed” in recent weeks.
In Britain 154 people suffering from swine flu have now died since the pandemic began in April.
There are currently 172 people in intensive care with the virus, up from 157 last week, while the number of hospital cases rose overall from 751 to 848, similar to levels seen during the first peak in July.
The Department of Health is also publishing new advice for doctors on how to recognise severe symptoms in pregnant women suffering from swine flu.
Medical staff should be on the lookout for a raised heartbeat or shortness of breath, according to the guidelines.
