The California State Assembly has passed a controversial bill that orders vaccination for school children and prohibits exemptions based on personal or religious beliefs of parents.

SB 277 amended California's Health and Safety Code and now requires immunisation for all kids that will be admitted to any public or private elementary or secondary school, child care centre, day nursery, nursery school, family day care home, or development centre.

The bill seeks total immunisation against diphtheria, hepatitis B, haemophilus influenzae type b, measles, mumps, pertussis (whooping cough), poliomyelitis, rubella, tetanus and varicella (chickenpox). It exempts vaccination of school children for medical reasons.

SB 277 was passed by the California State Assembly last June 25 with a 46-31 vote after being passed by the state Senate last May 14.

Because the Assembly passed it with amendments, the bill was returned to the state Senate for concurrence.

After that, it will be up to Gov. Jerry Brown to sign the measure into law. Brown has not issued any statement on whether he will do so.

The California Catholic Conference said although it "has not taken a position on SB 277," Catholic parents have the right to decide on the morality of certain vaccines.

"The Catholic Church has made it very clear that we must all be free to follow our conscience and that parents are primarily responsible for their children. It also teaches that respect and promotion of families must be one of the paramount drivers of public policy," it said.

The conference said "Catholics must inform themselves and follow their conscience with regard to vaccinations."

It is particularly concerned about the morality of using vaccines using "descendant" cells of aborted foetuses.

The Congregation for the Doctrine of the Faith (CDF) said, "There is a grave responsibility to use alternative vaccines and to make a conscientious objection with regard to those which have moral problems."

The National Catholic Bioethics Center said there are certain vaccines that are made in descendent cells of aborted foetuses and recommends the use of alternative vaccine if there's one available.

It said vaccines for rubella, varicella and hepatitis A have cell lines that have distant association with abortion.

The centre recommends that "one is morally free to use the vaccine regardless of its historical association with abortion."

"The reason is that the risk to public health, if one chooses not to vaccinate, outweighs the legitimate concern about the origins of the vaccine," it said.

Sen. Richard Pann, one of the authors of SB 277, said the concern by parents about vaccination came from misinformation such as the retracted 1998 study about the link between autism and measles vaccine. Andrew Wakefield, the study's author, was later found to be lying.

If SB 277 becomes a law, California will be the 33rd state that will not allow parents to opt out of vaccination because of personal belief exemption.