NEW YORK—At a small gathering in Times Square today, actor Amanda Peet teamed up with the United Nations Foundation* to launch a vaccination public service announcement. The Shot@Life ad is now airing on the square's iconic Toshiba screen.

In the past, Peet has worked with organizations such as Every Child By Two to advocate for child immunizations in the U.S. The Shot@Life campaign, timed for Mother’s Day, is meant to highlight how Americans can help save the lives of children in developing countries by donating money for vaccinations.

“If we take all of the children [in the U.S.] who are entering kindergarten this fall, a little fewer than half of that number is how many children die each year from vaccine-preventable diseases,” Peet said, referring to measles, polio, pneumoccocal disease and rotavirus, which are the world’s leading causes of death for children younger than five years. “What moves me about this cause is the fact that we have a cure. We have the medicine—we just have to get it to the children.”

More than 50 bloggers from to the World Moms Blog network have dedicated themselves to the campaign. These Moms stand in contrast to “anti-vax” parents who mistakenly believe that vaccines cause disorders such as autism and ADHD. “I understand their concern,” said Paul Offit, a University of Pennsylviania professor and pediatrician who specializes in infectious diseases and co-invented the rotavirus vaccine. “But when studies show that vaccines aren’t associated with that concern, and people still don’t believe it, that’s what gets frustrating. It’s not scientific illiteracy, it’s scientific denialism.”

When posts on Shot@Life blogs draw comments from anti-vaxers, the community rallies behind science, as demonstrated in this blog post’s comment section.

But it’s a different debate in developing countries, said Jennifer Burden, editor and founder of the World Moms Blog. “Here in the U.S., we don’t have to worry so much, because if our child gets severe diarrhea, we can take them to the hospital and they can get an IV and survive. Whereas in remote areas or places that don’t have access to those things, a vaccine is the lowest-cost way for these kids to have a shot at life.”

In the U.S., growing pockets of parents who refuse to vaccinate their children are suspected of weakening "herd immunity" in some parts of the country. Vaccine campaigns rarely can reach every single child, but widespread vaccination breaks chains of infection. When parents resist getting their children inoculated, outbreaks of such diseases as whooping cough and measles are more likely to occur.

“When we make a choice not to vaccinate ourselves, we’re also making a choice to put others who come in contact with us at risk, including those who can’t be vaccinated,” Offit said. “We have a social responsibility for our neighbors.” Including, it seems, our neighbors in other parts of the world.

*An earlier version of this article incorrectly stated that Peet teamed up with the World Health Organization.