The current vaccination rate in 3-year-olds is 86%, below the 95% level needed to prevent the spread of the virus.
A WHO official this week said repatriation is one of multiple factors fueling rises in Pakistan and Afghanistan.
As a steady polio rise continues in Pakistan, the country has now reported 45 cases this year.
PAHO says it will provide countries in the Americas with affordable access to respiratory syncytial virus vaccine.
Afghanistan and Pakistan reported more WPV1 cases, as 3 African countries report more vaccine-derived cases.
Pakistan and Afghanistan report wild poliovirus type 1 cases, and Chad, Niger, and Nigeria report circulating vaccine-derived poliovirus type 2 cases.
To date, 442,855 children under 10 years have been successfully vaccinated in central and south Gaza.
The first phase of Nigeria's campaign will begin in November, targeting Kebbi and Beyelsa states, where malaria activity is especially high.
Genetic sequencing hasn't found a link to similar viruses elsewhere, and no related illnesses have been reported.
At least two doses of the novel oral polio vaccine type 2 are needed to interrupt transmission
