MediMedia's companies, including leading medical journals such as Le Quotidien du Medecin and Le Generaliste, will become part of United-owned CMPMedica France.
Lord Hollick said of the acquisition: "Healthcare is now the largest sector served by United and prospects for growth in the 23 markets we cover, and in the increasing range of products we offer, are most promising."
The deal signals the refocus of United, which is about to come under the control of David Levin, who joins from software firm Symbian in April.
Coupled with the completion of the MediMedia deal, expected to take a few months, it is unlikely Lord Hollick will be looking to sell the £250m market research business before he leaves United.
According to reports last weekend, Lord Hollick was planning to sell off NOP World before May.
A report in the Mail on Sunday suggested that the sell-off was prompted by Levin's arrival. He is said to be less enthusiastic about market research than Lord Hollick, who helped build NOP into one of the world's top firms.
There have been no statements from the company since the reports and no hard evidence has been produced.
NOP is best known in the UK for its political polling work and it has long partnered with the BBC and the Labour Party. It recently, along with rival Mori, signed a deal with the BBC and ITV News to do a joint exit poll for the next general election to minimise the risk of calling the wrong result.
NOP World would be a prize for any group. It is one of the world's top 10 market research firms, with brands including NOP Research Group, Strategic Marketing Corporation, Mediamark Research Inc, Roper/ASW, Market Measures/Cozint and Allison Fisher.
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