Which of the following is a source of free print materials that can be used to market vaccination services?

The Centers for Disease Control and Prevention (CDC) is a key resource for public health information, including vaccinations. They provide free print materials that healthcare providers can utilize to promote vaccination services effectively. These materials include brochures, posters, fact sheets, and other educational resources that are designed to raise awareness about the importance of vaccinations and to inform the public about available vaccines. By accessing resources from the CDC, healthcare practitioners can ensure they are using evidence-based information to educate patients and encourage them to get vaccinated.

The other organizations listed, while they contribute to public health and may offer valuable resources, do not primarily focus on providing free print materials specifically for marketing vaccination services. This makes the CDC the most appropriate choice for sourcing such materials.