MONICA KAYOMBO, Lusaka
DESPITE maintaining its polio-free status since 1990, Zambia has recorded sporadic detections of polio virus cases, highlighting ongoing immunity gaps in specific populations.
To date, three circulating vaccine-derived poliovirus (cVDPV) cases have been identified among children under five years of age in Luapula Province, North-Western Province, and Western Province.
Dr Musole Chipoya, Lead Vaccine Preventable Diseases Epidemiologist at the Zambia National Public Health Institute (ZNPHI), said in an interview that environmental surveillance has also detected poliovirus in wastewater samples from the Copperbelt Province, indicating possible silent circulation in the absence of widespread paralytic disease.
“In response, Zambia has rapidly activated its polio outbreak preparedness and response mechanisms, including enhanced acute flaccid paralysis (AFP) surveillance, expansion of environmental surveillance, targeted outbreak response supplementary immunization activities (SIAs) using novel oral polio vaccine type 2 (nOPV2), and intensified risk communication and community engagement,” Dr Chipoya said.
She said these measures, implemented in close collaboration with national and international partners, aim to interrupt transmission, close immunity gaps, and sustain Zambia’s polio-free status. Oral Polio Vaccine (OPV) has been the cornerstone of global polio control and eradication efforts for decades, playing a pivotal role in preventing polio cases and deaths worldwide, including among children under five in Zambia.
The Global Impact of OPV has resulted in averted cases and deaths. According to published evidence, the Global Polio Eradication Initiative (GPEI) estimates that since the launch of the eradication program in 1988, OPV and associated immunization activities have prevented 19 million cases of paralytic polio globally.
“Through routine immunization and extensive supplementary immunization activities (SIAs), OPV has contributed to the averting of hundreds of thousands of deaths in children under five by preventing lifelong paralysis and its complications, such as respiratory failure and severe disability,” Dr Chipoya explained.
She said in order to improve OPV coverage and reduce transmission risks, Zambia is implementing a comprehensive, risk-based approach to improve vaccination coverage and reduce the risk of polio transmission.
Dr Chipoya explained that the efforts focus on strengthening service delivery, cold-chain, and data use to prevent the accumulation of susceptible children.
“Big Catch-Up initiatives and biannual Child Health Week activities are used to rapidly close immunity gaps among under-immunized children,” Dr Chipoya said.
She said in the event of poliovirus detection, Zambia conducts targeted supplementary immunization activities (SIAs) to rapidly interrupt transmission.
Dr Chipoya said Zambia collaborates closely with neighbouring and regional countries to prevent cross-border poliovirus transmission through formal coordination mechanisms led by the World Health Organization (WHO)-AFRO and established cross-border surveillance and response platforms.
“This collaboration includes regular information sharing, joint risk assessments, synchronized surveillance strengthening, and coordinated outbreak responses in border districts with high population mobility,” Dr Chipoya explained.
She added that Environmental surveillance is a critical complement to AFP surveillance in Zambia, as it can detect silent circulation before clinical cases occur, providing an early warning signal that guides timely risk assessment and targeted immunization responses.
Dr Chipoya observed that the biggest challenges to achieving high polio vaccination coverage in Zambia are largely driven by geographic, socioeconomic, and health-system factors, including hard-to-reach and border communities, mobile populations, health-system constraints, and the presence of missed and zero-dose children.
However, these challenges are being addressed through strengthened routine immunization systems, improved micro-planning and data use, catch-up platforms, targeted supplementary immunization activities, and expanded community outreach, supported by sensitive AFP and environmental surveillance.
Dr Chipoya observes that Zambia’s AFP surveillance system is the cornerstone of polio detection, designed to identify any child under 15 years of age presenting with sudden onset of flaccid paralysis, an early clinical signal of possible poliovirus infection.
She also said Community health workers play a significant role in Zambia’s polio prevention and response efforts, serving as the critical link between the health system and communities, particularly in hard-to-reach and underserved areas.
Dr Musole Chipoya, ZNPHI Lead Vaccine Preventable Diseases Epidemiologist
