The number of compulsory vaccinations will be reduced from 12 to ten, while financial penalties against parents who fail to vaccinate their children will be significantly reduced.
The amendments made in the Italian Senate also scrap the obligation to report parents who don't comply with the law to authorities - a move which could, in extreme cases, have left parents at risk of losing custody.
Now the decree must be passed in Italy's Chamber of Deputies, where further amendments could be added, but it seems likely to be passed due to the fact the Italian Higher Institute of Health (ISS) has given its approval to the law in its current form.
"[The amendments are] fully in keeping with tackling the country's epidemiological problems," said the president of the ISS in a letter of support.
Parents wishing to enrol their children in nursery must ensure they have been vaccinated against polio, tetanus, diphtheria, hepatitis B, Haemophilus influenzae B, whooping cough, measles, mumps, rubella and chickenpox. Meanwhile, the vaccines against meningitis B and C, pneumonia and rotarivirus have been downgraded from compulsory to 'recommended', though they will still be offered free.
This set of vaccines is compulsory for enrollment to state schools for children aged up to six, while parents of older children will face a fine if their offspring haven't had the jabs. However, these fines have been reduced by more than a third, thanks to an amendment cutting the maximum penalty from €7,500 to €2,500.
Within three years of the decree law, it will be possible for the list of ten to be either further reduced or increased, depending on new medical data and levels of vaccine coverage, which will be monitored by a government committee. For example, if the rate of coverage for one of the currently compulsory vaccines rises to above 95 percent, it may be removed from the list.
Measles cases rose more than fivefold across Italy in April, compared to the same month last year, the National Health Institute said at the start of May, with a growing anti-vaccine movement believed to have contributed to the increase.
Meanwhile, up to 20,000 children in Treviso, northern Italy, are thought to be at risk of infectious diseases following revelations that an Italian nurse 'pretended' to administer vaccines while really throwing away the phials.
Italy was one of the countries where discredited claims of a link between the combined measles, mumps and rubella (MMR) vaccination and autism had a significant impact on public perceptions of the safety of the jab.
But Italy's Five Star Movement party has also been heavily criticized for its role in raising doubts over the efficacy of vaccinations.
"There is nothing to support this lie," said Grillo in his blog, despite the fact that in 2014 the party proposed a law calling "for better information and possible denial of administering vaccinations" - with Grillo one of the signatories.
The proposal included the line: "Recent studies have brought to light the link between vaccinations and specific illnesses such as leukaemia, poisoning, inflammation, immunodepression, inheritable genetic mutations, cancer, autism and allergies."