SAN DIEGO -- "He's so little," says Leah Gove of her 10-day-old son, Greyson. "I can't imagine giving him, you know, four different shots all at one time."

Parents are concerned about vaccinations. Doctors, meanwhile, are divided on the subject.

Dr. Bob Sears (AskDrSears.com), a pediatrician in San Juan Capistrano, Calif., says, "My biggest worry is giving three or four vaccines that all contain similar chemicals and overloading a baby that way all together."

"What worries me is that people are going to make a bad decision and regret it later," says Dr. Mark Sawyer, Pediatric Infectious Disease Specialist at Rady Children's Hospital in San Diego, and professor of pediatrics at UCSD School of Medicine.

At the heart of this debate are not vaccines themselves, but the schedule in which they're given.

"I personally think that vaccines are very safe and they're very effective. And the ingredients in vaccines I think are okay, when they're given not too many at a time," says Sears.

Sears published "The Vaccine Book" in 2007. It explains an alternative vaccine schedule that he developed.

"I've been doing it for many, many years and there are a number of doctors around that want to do it, but most doctors won't because it's going outside the box -- vaccinating in a way that the American Academy of Pediatrics and the Centers for Disease Control doesn't approve," says Sears.

Sears limits shots to two at a time. By contrast, the AAP recommended schedule sometimes gives five immunizations in one sitting.

"To me it just makes better sense to spread those out, give fewer chemicals at a time and probably see fewer reactions," says Sears.

When it comes to the live virus vaccines – measles, mumps, rubella, chickenpox, rotavirus, nasal-spray flu -- Sears believes you should only give one live virus at a time. The AAP schedule recommends four live virus vaccines in one visit. For instance, a one-year-old would receive immunizations for measles, mumps, rubella, chickenpox and hepatitis A on the same day with the AAP schedule -- four of the five are live virus vaccines.

"I give the vaccines one at a time, (with measles, mumps and rubella) spread out each by about a year, so a child's immune system is getting the disease - or exposed to the disease - in a more natural way like nature intended. And I think I see fewer reactions to these vaccines by doing it that way," says Sears.

A growing number of parents are interested in alternative vaccine schedules, fueled by concerns over possible connections between serious side effects and vaccines.

"We wanted to protect our community and we wanted to protect our daughter, but we wanted to do it in the safest way possible for her," says Kelli Russell. She and her husband Kevin follow an alternative vaccine schedule created by Dr. Stephanie Cave for their two-year-old daughter.

"I got nervous about a lot of scares in the community. There was the MMR scare possibly being associated with autism. And although most of those have been repudiated, I still wasn't willing to risk it. So we separated out our MMR," says Kelli.

Although they found a pediatrician willing to work with them, Kelli found it wasn't easy to actually implement the alternative schedule. For instance, finding the individual doses of measles, mumps and rubella vaccines became her responsibility. Because the AAP schedule calls for giving the vaccines for measles, mumps and rubella at the same time, the combination shot with all three vaccines is easy to get, but individual doses of each vaccine is not.

Kelli explains, "MMR separated was nearly impossible. I called at least 20 different clinics. I tried travel clinics; I tried the CDC; I tried hospitals; I tried the little mom and pop clinics. After a while, I just knew - I felt like I wasn't going to find it."

After abandoning the search, she later started all over again and finally succeeded in finding the three separate vaccines. Dr. Sears worries that other parents who face challenges to their desire to vaccinate differently may decide to skip some shots – like measles, mumps and rubella -- all together.

"Whereas if the American Academy of Pediatrics encouraged doctors to tell these patients, okay, I'll work with you; let's find a vaccination schedule that you are happy with. Let's spread the shots out. If the AAP supported that approach and that option, to these parents that otherwise are not vaccinating, we'd have these babies vaccinated," says Sears.

The I-Team asks the AAP if they could consider giving parents an option of a different vaccine schedule. The group's spokesperson on the issue, Dr. Paul Offit - Chief of Infectious Diseases at Children's Hospital of Philadelphia - says essentially, no.

"All Dr. Sears' schedule does is delay or separate or withholds vaccines from children who need them. So although I think one does with his schedule eventually get all the vaccines you need, by delaying those vaccines all you're doing is increasing the period of time during which children are susceptible to vaccine preventable diseases without any benefit," says Offit. "So why should the AAP or the CDC offer a schedule which can only be deleterious to the child without any benefit? There's no logic to that."

Dr. Sawyer, in addition to his positions at Rady Children's Hospital and UCSD School of Medicine, is also one of 15 voting members of the Advisory Committee on Immunization Practices, or ACIP. It's part of the Centers for Disease Control and Prevention and gives advice on the national recommendations for immunizations. He also believes that delaying vaccines is dangerous.

"I've seen kids die of chickenpox. I've seen kids on ventilators for measles. I've seen meningitis lead to brain damage and deafness. And until you see that and appreciate that, you're missing a big part of this equation. And I'm afraid that parents don't realize the risks that they're leaving their kids at when they choose to delay vaccines," says Sawyer.

Sears says he does all the important shots first…not wishing to risk the child's health.

"There are some diseases that are very risky and very deadly and more common. And a vaccine for that kind of disease is obviously going to be much more important. And I really focus on those vaccines first in my office. We're talking vaccines for meningitis, vaccines for whooping cough, vaccines for rotavirus, which is a severe intestinal infection. Those I consider the most important vaccines."

Sawyer says he sees no indication that the AAP vaccine schedule creates problems.

"I'm not aware of any data at all that suggests spreading the vaccines apart is necessary."

Not everyone has the same trust in data.

"With any study, depending on who it's funded by and where it's coming from, empirical evidence is such a thing that it can have a sway," says parent Kevin Russell.

Offit agrees that not all studies are equal.

"I think if you look at published studies that are excellent, meaning excellent studies that are well peer-reviewed, that appear in excellent journals, where you read the materials and methods section of that paper and realize that this is a strong, valid, internally consistent study which has been reproduced over and over again, that you can take comfort in that study."

Some question whether vaccine manufacturers -- the pharmaceutical companies -- have too much financial influence with vaccine decision makers. Offit says they don't.

"The way they work at those [ACIP] meetings, if you have done research in collaboration with a pharmaceutical company, or you're the co-inventor of a vaccine - which is what I am and was on the ACIP - you're not allowed to vote on that particular product or on any product with which that product would compete. It gets the conflict of interest issue on the table," says Offit.

However, the conflict about vaccine schedules remains. Kelli Russell understands Dr. Sawyer's worries.

"I would be nervous to see if everybody decided to slow down the rate of vaccines or forget vaccines all together, we might see more increase in disease and that's a little scary."

And Dr. Sawyer understands the fears parents have about vaccines.

"There are tiny subsets of people that are susceptible to things in vaccines or in medications that we don't know about."

But each side feels differently about which risk is more tolerable for the children that they all want to protect.

To learn more about the opposing views on alternative vaccine schedules – including the debate over aluminum in vaccines – please read the I-Team blog on the topic.

To read the blog, click here.