El Switch en las Américas

Polio Vaccine Switch: A Historic Step Towards Eradication

Introduction to the Polio Vaccine Switch

• In 2016, 155 countries and territories initiated a historic global health initiative aimed at eradicating polio by switching from one type of oral vaccine to another.

• The event marked a significant transition from the trivalent oral polio vaccine (TOPV), which protects against all three types of poliovirus, to a bivalent oral polio vaccine (BOPV).

Rationale Behind the Vaccine Change

• The switch was necessary as wild poliovirus type 2 has been declared eradicated; thus, it was removed from the vaccine to maintain high vaccination coverage and reduce risks associated with any remaining strains.

• This strategic plan, approved by the World Health Organization in January 2013, aims not only to eliminate wild polioviruses but also vaccine-derived polioviruses.

Understanding Oral Polio Vaccines

• The TOPV is produced by weakening live polioviruses, effectively preventing disease while still posing a minimal risk of reverting to an active form that can cause paralysis.

• BOPV protects against types 1 and 3 of polio. The continued use of TOPV posed more risks than benefits due to its association with vaccine-derived cases.

Implementation of the Switch

• Between April 17 and May 1, 2016, countries globally replaced TOPV with BOPV. This coordinated effort involved suspending TOPV usage simultaneously across nations.

• Countries agreed on this timeline due to lower transmission rates during this period, minimizing potential virus exportation.

Ensuring Safety During Transition

• To protect children against type 2 strains post-switch, inactivated polio vaccine (IPV), which cannot mutate or cause related cases, was introduced prior to the change.

• IPV provides immunity against all three types of poliovirus but must be used alongside BOPV for effective intestinal immunity and prevention of disease spread.

Support for Countries During the Switch

• A working group formulated technical guidelines and training materials for regions transitioning away from TOPV.

• The Pan American Health Organization played a crucial role in adapting these materials regionally and providing technical support throughout the process.

Conclusion: Monitoring and Verification

• Post-vaccination efforts included creating checklists for countries ensuring compliance with all steps necessary for a successful switch.

Vaccination Transition and Polio Eradication Efforts

Transition from Trivalent to Bivalent Vaccine

• The transition involved the removal of trivalent vaccines, ensuring none remained in circulation on National Switch Day. All trivalent vaccines were withdrawn from cold storage and labeled for disposal.

• Countries that are members of the Pan American Health Organization (PAHO) took responsibility for controlling 100% of vaccination services to prevent any remaining trivalent vaccines from being used mistakenly.

• Post-eradication, only polioviruses necessary for vaccine production or research will remain in laboratories, emphasizing the need for strict containment measures.

Ensuring Global Safety and Preparedness

• To maintain a polio-free world, it is crucial to ensure that existing polioviruses are securely contained to prevent accidental or intentional release.

• Every country must have an updated response plan for potential polio outbreaks now that wild-type poliovirus has been declared eradicated. Any detection of vaccine-derived poliovirus type 2 will be treated as a global public health emergency.

Success Stories and Collaborative Efforts

• Jamaica's switch was deemed successful due to extensive planning at various levels, including regional teams established for effective monitoring before and during the switch day.

• The success relied heavily on national funding sources and the role of the Revolving Fund in Latin America, which facilitated access to timely and quality vaccines through negotiations with producers.

Acknowledging Contributions

• The commitment of governments and thousands of healthcare workers across the Americas was pivotal. They actively sought out children needing vaccinations during this transition period.

• International organizations such as WHO, PAHO, CDC, UNICEF, Rotary International, Gavi Alliance, and the Bill & Melinda Gates Foundation provided essential support throughout this process.

Historical Significance

• This coordinated effort marks a unique moment in public health history where multiple countries synchronized their vaccination strategies against polio—an unprecedented achievement in global health efforts.