PAPUA New Guinea has joined 16 of its neighbours in making the switch to a new oral polio vaccine (OPV) in what the World Health Organisation (WHO) says is the largest synchronised event in the history of vaccines.

The change became necessary after one strain – type two – of the wild polio virus was eradicated in September 2015 – meaning that vaccination against it was no longer needed.

As a result, countries switched from trivalent OPV to bivalent OPV – containing vaccinations for the two remaining strains. Papua New Guinea made the switch on 18 April, reporting the change to the WHO in early May.

WHO regional director for the Western Pacific Shin Young-soo said this was the first time a changeover of this scale had been attempted, with 155 countries making the changeover simultaneously.

“We are pleased that member states in the Western Pacific were able to make all the necessary logistical arrangements to ensure a smooth transition,” Dr Shin said.

“We have successfully reduced the prevalence of polio by 99 per cent. But as we near the finish line we need to adopt new tactics to ensure we eradicate this disease.”

WHO is also supporting surveillance for polioviruses in member nations to document the elimination of type 2 poliovirus transmission and to detect any re-emergence of the polio strain, while also boosting response capacity measures.