The warfare over vaccines and autism is heating up yet again. This week, Alison Singer, the executive vice president of communications and awareness at Autism Speaks, one of the nation's leading autism advocacy groups, announced her resignation, citing a difference of opinion over the organization's policy on vaccine research. "Dozens of credible scientific studies have exonerated vaccines as a cause of autism," she wrote in a statement. "I believe we must devote limited funding to more promising avenues of autism research." Singer, who has an 11-year-old daughter with autism, joined the organization when it launched in 2005. Singer praised Autism Speaks and its founders, Bob and Suzanne Wright, but said she could no longer work for a group that supports spending limited resources on vaccine research. Calling Singer's resignation "disappointing and sad," Bob Wright says more authoritative research needs to be conducted on the safety of vaccines given to children under 2. "We all know that autism has genetic causes, but it's highly associated with environmental factors we can't get our hands around," says Wright. "Vaccines fall into that category." NEWSWEEK's Claudia Kalb spoke with Alison Singer about her resignation. Excerpts:

NEWSWEEK: Describe Autism Speaks.
Alison Singer: Autism Speaks is an amazing organization. It has really been a privilege for me to work there. Autism Speaks has raised so much awareness of autism and has supported literally thousands of families around the world. I could not be more proud of Autism Speaks and the work that we've done.

But you disagree with their vaccine position?
In general, I disagree with a policy that says, "Despite what this study shows, more studies should be done." At some point, you have to say, "This question has been asked and answered and it's time to move on." We need to be able to say, "Yes, we are now satisfied that the earth is round."

What do you believe the science shows?
There are more than a dozen studies that show no causal link between the MMR [measles-mumps-rubella] vaccine and autism, and thimerosal [a mercury-containing vaccine preservative] and autism. Over and over, the science has shown no causal link between vaccines and autism. My feeling is that if there was an unlimited pot of money at the NIH [National Institutes of Health] from which to fund autism science then it would be fine to say let's study it more. But we don't have that. We have very limited resources and every dollar we spend looking where we know the answer isn't is a dollar we don't have to spend where we might actually find new answers. In general, yes, more research is always better than less. But again, we have limited dollars to spend and we have to use our limited money wisely in ways that are likely to yield new information for families.

How confident are you in the studies that show no vaccine-autism link?
I've read the studies and I've talked to many doctors. One thing that has been a hugely wonderful part of being at Autism Speaks is that I've been able to consult with the top scientists in the field. We work with the top minds. I think that there's this feeling [among some parents] that the vaccine decision is a choice between, "Do I want to risk measles or do I want to risk autism?" That's not a good characterization. We know for a fact that the measles vaccine reduces the risk of getting measles. One choice is backed by science, one choice isn't.

Where would you like to see the research money go?
I think the genetics work has the potential to point us toward important answers. When we can determine which proteins are associated with various genes we can start to understand the mechanism of action that causes autism. Once you understand the mechanism of action, you can start to look for targeted therapies. I would also focus on prenatal exposures. What is a mom exposed to during pregnancy with regard to hormones or maybe medications or even pesticides? Or what's happening in the environment? During flu season, people are more prone to infections so we should look at the incidence of viral infections, flu, hormonal fluctuations and toxins in the environment for both mother and baby.

How is your daughter doing now?
Jodie has benefited tremendously from applied behavioral analysis therapy. She has learned to have some actual communicative speech. She's able to make her wants and needs known. That's really a breakthrough. For three years, she was in private school that focused intensively on language. She gained enough skills to be in a special class in a public middle school. She's not mainstreamed, but she's able to be in that large environment. So she's making great progress.

What do you think caused your daughter's autism?
Jodie had difficulties from the day she was born. She cried constantly, she had difficulty feeding, difficulty sleeping. She was diagnosed in the first few days as having "failure to thrive." I also have a brother diagnosed with autism. He's 44. My first cousin has a son diagnosed with autism. I strongly believe that there is a genetic component.

What do you say to the families who believe their child's autism was triggered by vaccines?
It's very hard because people feel very strongly and love their families so much. But not all opinions are created equal. Some are based on fact and science and some are not. Do you remember when Jenny McCarthy went on Oprah? She said she doesn't need science. Her science is at home and his name is Evan. That's not science.

Here's another story. A few weeks ago, Jodie went to the pediatrician. She had Tdap [tetanus-diptheria-pertussis] vaccine, a flu shot and a vaccine against meningitis. The next day her teacher remarked to me that Jodie was much more attentive and participated in class much more than usual. Her gym teacher said that for the fist time Jodie was able to compete in an obstacle course. Should I start pontificating that vaccines are a great treatment for autism? Of course not, that's not science. That's called coincidence.

Some families want more money spent on services for people with autism. Thoughts?
I think that's true. There's a growing number of people with autism and they're going to need services and supports. We really need to think about autism as a lifespan issue. We need to start planning now for our children's future.

placeAd2(commercialNode,'bigbox',false,'') What about federal health officials? Some scientists have critiqued them for not being outspoken enough about vaccine safety. Do you agree?
I think the media has to start to change. In our culture, we love celebrities. We need to listen to experts and not actresses. The media culture, feeling compelled to give both sides of an argument has lent a legitimacy to the anti-vaccine movement that is very over-weighted. They're a small number of people with very loud voices. The vast majority of parents of children with autism are very supportive of the importance of vaccines. I've had hundreds of emails in last 24 hours from parents supporting me. The media need to show both sides to make it look like both sides are equal. One side is backed by evidence, one side is not.

I think the government needs to be more vocal and I think scientists have to be more vocal. Scientists are an interesting group. They are very reluctant to speak to the media. There needs to be change in that culture. Scientists need to be more comfortable speaking out about the good science being done. I think when we see the scientists speaking out more, we will see a change.

In an interview in 2006, you said, "I am planning to stay at Autism Speaks until the day we find a cure." Now what?
Now I'll revise that to say I plan to stay in autism advocacy. I plan to take all the energy and passion that I committed to Autism Speaks and apply it elsewhere in the autism advocacy community. I'm certainly not going to be leaving. If anything, I hope to be more vocal.

Will you become more vocal on the vaccine issue specifically?
I think by talking to you today I already have.