Zambia has reported its first local case of polio since 1995 after a two-year-old boy was paralysed by a virus derived from the vaccine.
The VOA said that in a report this week, the World Health Organization (WHO) said the case was detected at the border with Congo, which this year reported 37 cases of polio traced to the vaccine.
The United Nations health agency said there is no established link between the Zambia case and the ongoing Congo outbreak but noted the need for increased surveillance and vaccination efforts.
It warned that "there is a potential for international spread".
In rare cases, the live virus in the oral polio vaccine can mutate into a form capable of sparking new outbreaks.
The global effort to eradicate polio was launched in 1988 and originally aimed to wipe out the potentially fatal disease by 2000.
Nine African countries are currently battling polio epidemics linked to the vaccine as the WHO and partners struggle to keep their efforts on track.
Across the globe, cases have been reported in China, Pakistan, Afghanistan, Myanmar and the Philippines.
This year alone, there have been 72 cases of polio in Pakistan, a significant rise from eight in 2018.
Last Thursday, the UN said that Nigeria, a third polio-endemic country, has gone three years without a reported infection.
This places the country on track for certification as polio-free by 2020.
Kenya's dream of becoming a polio-free country was dimmed after live viruses were found in sewage samples collected from Nairobi in 2018.
The Kenya Medical Research Institute (Kemri) notified the Ministry of Health of isolation of polio virus type 2 from an environmental sample collected on March 21 from one of the sites in Eastleigh, Kamukunji Sub-county.
"Genetic sequencing of the isolate in CDC Atlanta laboratories subsequently confirmed it is circulating vaccine-derived polio type 2(CVDPV2)." the ministry said in a statement.
This means an unvaccinated person who comes into contact with the stool or respiratory secretions of the infected person can get polio.