Police have arrested a person for putting out a contract on a trainee doctor who supported vaccination online.

Bernard Leenstra, who also co-founded an initiative to offer spare vaccines without appointment to stop them being thrown away, announced the arrest on Twitter, thanking police ‘also on behalf of my family’.

The man or woman – police have not released any details about the perpetrator – posted a message on the internet saying: ‘I offer €1000 to finish off doctor Bernard’.

Leenstra said the message was probably a bluff but reported it to police because ‘my mother and girlfriend read this too. That is something that gets to you,’

The person was probably angry or does not realise what the consequences of his actions are, Leenstra said. However, threats like this cannot be ignored. ‘It only takes one person to take this seriously,’ he said.

Police have since confirmed a 21-year-old man from Hoeksche Waard in Zuid Holland was arrested for incitement and making online threats but declined to say if Leenstra was the object, Nu.nl said.

Family doctors have been reporting an increasing number of incidents, ranging from intimidation to attacks. One practice in Leiden was firebombed and shot at in September last year.