Haiti, Nigeria, Ghana -- 180 countries in all -- stepped up their immunization drives against deadly childhood infections to mark World Immunization Week. 

The GAVI Alliance -- a Geneva based public-private partnership aimed at improving health in poor countries -- rolled out new vaccination campaigns in many countries against killer childhood infections such as diphtheria, tetanus, pertussis, measles, mumps and rubella.

Spokesman Jonathan Stern says the GAVI Alliance has helped to vaccinate 326 million children around the world since 2000, a campaign that has saved about five and a half million lives.

“Our goal for 2015 is to immunize an additional quarter billion people and this would save nearly another 4 million lives. And so for GAVI, the real challenge is fulfilling that promise -- that is, to immunize a quarter billion people,” Stern said.

Experts say the current immunization campaign provides a unique opportunity to highlight the powerful impact vaccines can have in reducing mortality and illness. 

“The leading killers of children in the world now are diarrheal disease caused by rotavirus infection or respiratory diseases caused by pneumococcal pneumonia. So for both those killer diseases, we have safe and affordable vaccine we need to greatly expand their use,” said Dr. Peter Hotez, president of the Sabin Vaccine Institute. He says vaccines have made it possible to eradicate smallpox and other diseases, but their primary value is that they provide an extremely cost-effective way to prevent and control fatal or disabling diseases such as polio or measles.

“When we are talking about saving lives and reducing morbidity and mortality from infectious and neglected diseases our first goal is generally not eradication. That’s a nice target but one which is still decades away,” he said.

Researchers are hopeful an effective malaria vaccine will be ready soon, and in the next few years, a vaccine against tuberculosis. Hotez is confident these new vaccines -- along with new combination drugs and aggressive vector control strategies -- will help to reduce the terrible human costs of preventable and treatable diseases.