(A local health worker carries vaccination kits into a vehicle at a distribution centre ahead of the start of a nationwide polio immunization campaign  in Lagos February 21, 2011. REUTERS/Akintunde Akinleye)

The following is a guest contribution. Reuters is not responsible for the content and the views expressed are the authors’ alone. Mercy Ahun is Special Representative to Eligible Countries for GAVI, a public-private partnership that works with governments, vaccine producers, civil society organizations and others to expand access to vaccines and immunization in the developing world.

By Mercy Ahun

Attacks on polio immunization workers in Pakistan have drowned out the celebrations of so much recent success in immunization work. Pakistan remains one of only three countries in the world where polio still exists, but efforts to bring vaccines to all corners of the country have been politicized to a tragic extent.

In almost every country in the world—including Pakistan—expanded access to old and new vaccines has saved hundreds of millions of children’s lives. Working together since 2000, global organizations, country governments and civil society have prevented more than five-and-a-half million deaths.

Newer vaccines have just begun the task of protecting children against pneumococcal and diarrheal diseases, among others. We’re also on the verge of achieving eradication of polio. Yet as we celebrate our success, we’re also saddened by the tragic murders of health workers not just in Pakistan, but in Nigeria, South Sudan, and other insecure countries.