California Gov. Gavin Newsom has signed bills to crack down on doctors who write fraudulent medical exemptions for children's vaccinations.

The Democratic governor acted less than an hour after lawmakers on Monday sent him changes he demanded as a condition of signing an earlier vaccine bill.

Lawmakers passed the second of the two bills despite protesters' efforts to disrupt the proceedings.

Newsom last week called for more changes to legislation aimed at doctors who sell fraudulent medical exemptions.

Lawmakers sent Newsom that bill last week. Sen. Richard Pan agreed to carry follow-up legislation giving school children grace periods that could last several years on existing medical exemptions.

Opponents delayed Assembly and Senate sessions, shouting their opposition. Several were detained as they blocked entrances to the Capitol in Sacramento.