What is the vaccine switch?
The oral polio vaccine switch is a globally synchronized event and a critical step towards polio eradication. It involves replacing the trivalent oral polio vaccine (tOPV), which protects against three type of poliovirus (types 1, 2 and 3), with a new bivalent vaccine (bOPV) that will provide greater immunity against two types of polio (types 1 and 3). bOPV is exactly the same as tOPV in terms of route of administration and immunization schedule, but does not contain the type 2 poliovirus component. The switch will also involve disposing of all batches of the old vaccine so that it is no longer being used anywhere in the world.
Why is it happening?
Use of tOPV led to the successful eradication of type 2 poliovirus from the world in 1999. In rare cases, in areas with low routine tOPV coverage, the ‘type 2’ component of tOPV can still cause vaccine-derived polio viruses, which can cause paralysis, the same way that wild polio virus does. Therefore, to fully eradicate polio, all oral polio vaccines will be phased out entirely. This will start with the removal of the type 2 component of tOPV, and a switch from tOPV to bOPV in April 2016. In the future, bOPV will also be phased-out and only inactivated polio vaccine will be used.
When is it happening?
In April 2016, all immunization staff, at all levels, in every country using OPV, will work together to protect the world’s children against polio. In a two-week period from 17th April – 1st May 2016, all countries that use the OPV will switch from tOPV to bOPV; the switch day for Bangladesh is 23rd April, 2016.
How is WHO helping?
WHO is providing technical guidance to countries for the smooth withdrawal of tOPV from the supply chain and introduction of bOPV. WHO Country Office for Bangladesh is working closely with the Expanded Programme on Immunization to recall all trivalent vaccines and distribute the new vaccines. WHOs network of Surveillance Medical Officers (SMO) is providing technical support and also ensuring that the old vaccines are disposed of safely.