JOANNE SILBERNER: This is Joanne Silberner. When it comes to her new baby, 37-year-old Elise VanderMere(ph), of Atlanta, feels like most parents.
Ms. ELISE VANDERMERE: Shes the love of my life, and I would do absolutely anything, anything to protect her.
(Soundbite of baby babbling)
SILBERNER: And when Lena Rose was born seven months ago, Elise had a decision to make about her healthy baby: Should she immunize her?
Ms. VANDERMERE: Im a little intimidated by the schedule. There are 24 shots scheduled in a two-year period, and that is not including the flu shot. So it is a concern.
SILBERNER: A survey 10 years ago showed that a quarter of parents were concerned that vaccines might be too much for a babys immune system. But when you look at the biology, it seems less daunting. Even fetuses have immune system cells, as early as 14 weeks' gestation.
Edgar Marcuse, a professor of pediatrics at the University of Washington, says one part of the immune system takes a little longer to kick in, but babies are born pretty much ready to go.
Professor EDGAR MARCUSE (Pediatrics, University of Washington): The infant immune system can respond to most everything. As soon as they're born, they are bombarded with all the things that exist in our world.
SILBERNER: He and some colleagues once calculated giving 11 vaccines all at one time - which no one does - would use up only 0.1 percent of the capacity of a baby's immune system. And even that would quickly regenerate.
Still, Elise VanderMeer wondered if she should at least space out the vaccines. So she talked to Lena Rose's pediatrician.
Ms. VANDERMEER: My doctor was actually very open. He said, you know, she's your baby. We'll do whatever you want. We'll be flexible. But he did advise me against it for two reasons.
SILBERNER: First, the number of office visits needed to give the shots one at a time.
Edgar Marcuse explains reason two.
Prof. MARCUSE: When you space out the vaccines, you leave your infant susceptible to diseases you could otherwise have prevented, particularly when they're most at risk, in the first six or eight months of life.
SILBERNER: Babies can get whooping cough. They can get meningitis, and these diseases can be very serious. But what about all those foreign substances going into babies' bodies, the viruses and bacteria or more precisely, the parts of them that are used to make vaccines? Well, vaccines now are cleaner than they used to be says Saad Omer of Emory University. He studies parents' concerns about immunization.
Dr. SAAD OMER (Emory University School of Public Health): A lot of people say that the number of vaccines has gone up. Actually, the number of antigens, which is the active part of a vaccine, hasn't gone up; it has gone down in the U.S. population.
SILBERNER: An antigen is a part of a virus or bacteria used in the vaccine. The five injections given to kids back in 1980 contained a total of about 3,000 different antigens. Twenty years later, there were 15 more injections, and the total number of antigens was down to about 125 - from 3,000 to 125. Another thing missing from childhood vaccines, that some parents worried could hurt their babies, is the preservative called thimerosal. That contains mercury.
Omer says one thing a lot of parents, they don't realize: Getting exposed to childhood infections is far worse than getting the vaccines. Take measles. Here's what that disease did to kids before there was a vaccine.
Dr. OMER: So what the study shows is that one in a thousand kids who got measles - so, measles infection - had brain damage, or an illness related to that. And one in 500 kids had a risk of dying - in this country; this is not data from, let's say, Nigeria or Bangladesh.
SILBERNER: The risk from getting the measles vaccine is a one-in-a- million chance of some brain damage. And deaths? The risk is too low to even calculate.
Both Omer and Marcuse say understanding the risks and benefits of vaccines is a lot of information for new parents.
Elise VanderMeer talked with friends, with her doctors. She read up as much as she could, and she's going ahead with Lena Rose's vaccines on schedule. But Elise admits, even though she knows it's the best thing to do, she says a few Hail Marys each time.
Joanne Silberner, NPR News.