Flu levels have dropped in England, but risen in Scotland
The number of new swine flu cases in the past week fell by nearly a quarter to 64,000 in England, figures show.
But experts warned against assuming the pandemic had peaked, saying it could be a "half-term effect" - flu rates tend to be higher when schools are open.
Chief Medical Officer Sir Liam Donaldson said next week's figures should give a fuller picture.
Meanwhile, in other parts of the UK there were slight rises as the number of deaths hit 182.
About 21,500 people are estimated to have caught the virus in Scotland up from 17,500 the week before.
Figures were much lower in Wales and Northern Ireland.
Sir Liam said: "We still can't interpret these figures. It could be the half-term effect."
There has also been a small drop in patients in hospital to 785, but Sir Liam said the figures still remained relatively high.
Children are seen as a key factor in the swine flu numbers.
They are often called super-spreaders because the way they play and interact mean they are more likely to pass on the virus.
So it was always expected that the half-term break at the end of October could have an impact.
The fall should also be seen in the context of what has happened elsewhere in the world.
Several weeks ago, the spread of flu seemed to be tailing off in the US, but since then it has shot up.
Shadow health secretary Andrew Lansley said the latest figures illustrated the importance of vaccinating children. "This is further evidence that we need to begin planning a school and college-based vaccination programme immediately."
Immunisations are already under way for priority groups, which include pregnant women and people with health conditions.
The government is expected to decide soon who will get the jab next.