Under the new law, children must now receive a range of mandatory vaccinations before attending school.
And fines as high as roughly $560 could also be implemented if older children - ages 6 through 16 - are unvaccinated, according to the BBC.
They include vaccinations for chickenpox, polio, measles, mumps, and rubella.
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"No vaccine, no school", said Giulia Grillo, the health minister.
The new rules came into force on Tuesday and are part of the so-called "Lorenzin law", named after former Italian Health Minister Beatrice Lorenzin.
In British Columbia, which is now experiencing a small measles outbreak, parents started a petition calling for mandatory vaccinations to attend school. The BBC added that Italian media reported regional authorities are "handling the situation in a number of different ways", with no notices of suspension reported in some areas and grace periods allowed in others.
Such conspiracy theories have repeatedly been discredited by researchers and have no scientific backing, though the numbers of people who believe in them have become significant enough that the World Health Organisation (WHO) deemed the movement one of the top 10 global public health threats of 2019. It threatened to overturn the mandatory vaccination law passed by the previous government but ended up scrapping its plans in the face of criticism as the country experienced a measles outbreak last summer.