PHOENIX  State health officials are urging counties to conduct mass vaccinations at public schools in an effort to get as many children inoculated against the novel H1N1 flu as possible.

But they won’t force the vaccines on anyone.

Will Humble, acting director of the Arizona Department of Health Services, said the goal is to get the vaccine to close to 80 percent of schoolage children. At that point, he said, their immunity will help protect the others who are not vaccinated.

But Humble told members of the House and Senate Health committees on Thursday that the vaccination rate for the regular seasonal flu  the only other comparison he has  is closer to 20 percent.

Humble reassured lawmakers, though, that no one who doesn’t want the inoculations against what has become more commonly known as the “swine flu’’ is going to be forced to get it.

“I have absolutely no intention of making this vaccine mandatory in any way, shape or form, whether it’s for school entry or otherwise,’’ he said. “It’s going to be strictly voluntary.’’

More to the point, Humble said schoolbased clinics will be legally precluded from giving the vaccine to any youngster absent a signed permission slip from a parent or guardian.

That still left Sen. Thayer Verschoor, RGilbert, uncomfortable.

“I know you say you’re not going to do that,’’ he said. “But when you start seeing these children dying, that changes the dynamics.’’

Humble acknowledged the governor does have certain powers in a “state of emergency.’’ But he said he doubts that could be legally triggered, even if 50 to 60 percent of Arizonans became infected.

He also said a mandate would only make the public suspicious that there’s something wrong with the vaccine. Instead, Humble said, he hopes to educate people why they should get inoculated.

Anyway, Humble said, there won’t be enough vaccine available to inoculate everyone.

While that comforted some lawmakers, the possibility that a large number of children who will be without protection concerned Rep. Phil Lopes, DTucson.

“You have to get to a certain level, do you not, in order for the ‘herd immunity’ concept to take place?’’ he asked. Lopes worried that enough parents would refuse the shots for their children, to the point that it would help spread the disease.

Humble said he is not spending a lot of time trying to reach any particular immunization level but rather focusing on making information available “so that parents can make responsible decisions that they believe are appropriate for their families.’’

“We’re hoping most families will decide to get their children vaccinated because, No. 1, it will protect their individual family,’’ he said. “But it also has, as you said, an added bonus in that it has a community effect if you can get the vaccination threshold into the 7080 percent range.’’

Lopes said, though, that goal is being undermined by what he said is irresponsible information on the World Wide Web claiming the vaccine is dangerous.

“Is it a pipe dream to think we can get 80 percent if we’re at 20 now?’’ he asked. Lopes said he is getting emails from parents who are “scared as hell about this and don’t want to do it.’’

Maricopa County Health Director Bob England said it will depend a lot on what is being reported in the media.

He said if there are lots of stories about “extremely rare side effects’’ of a similar vaccine from 33 years ago, then people will avoid the shots.

“If, in the media, there are stories about the children who are dying from this, then it will flip the exact opposite way and people will demand the vaccine.’’

“You guys hear that?’’ Lopes said to reporters and photographers at the hearing.

Beyond that, England said the question comes down to logistics: Even if lots of people want the vaccine for their children, how do you administer that many doses.

“The only rational way to hit the school-age population is to vaccinate them where they are, set up school-based vaccine clinics,’’ he said.

Rep. Nancy Barto, R-Phoenix, said there are questions about the effects of preservatives in the vaccines. Some people have said there is a link between autism and the preservative, known as thimerosal, which contains mercury.

Humble said there is an alternative for those who are concerned. He said while most vaccines are delivered in 10-dose vials, which have to have preservatives, there are single-dose syringes also available which do not need the extra chemicals.

“As for me, I wouldn’t care if my kid got the vial or the pre-filled syringes because I’m confident that the amount of preservative in the vial is negligible,’’ he said.

“But there’s parents who might be concerned about that,’’ Humble said.

“To overcome those objections, the pre-filled syringes are available,’’ he continued. “Either way, they get immunity.’’

Humble said, though, he is sure that some parents will still come up with other objections.

“Our job is to overcome as many barriers as we can and really speak as clearly as we can about the safety of the vaccine,’’ he said. “But, ultimately, it’s parents on their own that make those decisions for their families.’’

England said one reason for concentrating on inoculating children is that it appears many adults have some immunity from this virus based on their exposure to a strain that went around about 50 years ago. That is showing up in the fact that most of the hospitalized cases of H1N1 are children, compared with prior strains which have hit older adults harder.