Three babies infected with measles in The Netherlands, two were too young to be vaccinated, another should have been vaccinated but wasn't.
Three children at a crèche in The Hague have come down with measles and a fourth child may have the disease, public broadcaster NOS reports.
The children involved had not been vaccinated and one of them may have caught the disease when on holiday, the broadcaster said. One of the children is over the age of 14 months, when it should have been vaccinated against the disease, but the others are younger.
Community health service GGD Haaglanden has not revealed which crèche is involved but said the disease may spread and that it is looking into vaccinating children who are currently unprotected, including babies.
The children in The Hague bring the total measles cases in the Netherlands to 12 so far this year, compared with an average annual infection rate of 10 to 20. The disease is particularly dangerous for pregnant women and very small children.
The RIVM public health institute said that at the moment no link can be made between The Hague cases and the drop in the number of children being vaccinated in the Netherlands.
At the moment 90.2% of Dutch children are vaccinated against potentially serious illnesses such as measles, polio and whooping cough. This is below the level of 95% the World Health Organisation considers safe.
Vaccine uptake has been declining, prompting a government information campaignwhile daycare centres have been demanding the right to refuse children who have not been vaccinated. At the moment this is not yet legally possible.
The last measles epidemic in the Netherlands hit the Dutch Bible belt in 2013. In total, 2,600 people were diagnosed with measles and the outbreak was concentrated in families with young children who had not been vaccinated for religious reasons. One girl, who had not been vaccinated, died.