Vaccine-derived poliovirus: a threat under surveillance

13 février 2025

#Poliovirus #InfectiousDiseases #Vaccine #Vaccination #nOPVS2 #Immunity #cVDPV Circulating vaccine-derived polioviruses (cVDPVs) remain a persistent threat to public health, particularly in regions where vaccination coverage is insufficient. These viruses emerge when the attenuated strain of the oral polio vaccine (OPV) undergoes mutations after prolonged circulation within under-immunized populat

#Poliovirus #InfectiousDiseases #Vaccine #Vaccination #nOPVS2 #Immunity #cVDPV

Circulating vaccine-derived polioviruses (cVDPVs) remain a persistent threat to public health, particularly in regions where vaccination coverage is insufficient. These viruses emerge when the attenuated strain of the oral polio vaccine (OPV) undergoes mutations after prolonged circulation within under-immunized populations. This phenomenon occurs when herd immunity is too weak to halt transmission of the vaccine-derived virus, allowing it time to evolve into a neurovirulent form capable of causing paralysis.

The main challenge is interrupting their spread. Conflicts, political instability, and vaccine hesitancy hinder access to at-risk populations, limiting the effectiveness of public health interventions. Furthermore, the continued use of the oral vaccine, while essential for polio control, paradoxically maintains the risk of new cVDPV outbreaks. These issues underscore the urgency of strengthening vaccination strategies, particularly through the introduction of safer vaccines and targeted campaigns to reach vulnerable communities.

This study analyzes global cVDPV outbreaks between January 2023 and June 2024, identifying affected countries, the types of viruses involved, and the strategies implemented to control these outbreaks.

Can the mutant poliovirus be stopped in time?

A total of 74 cVDPV outbreaks in 39 countries were analyzed, assessing the types of polioviruses involved, the duration of transmission, and the strategies implemented to halt their spread.

The results reveal that 64% of the outbreaks, detected in 30 countries, are recent, indicating a concerning resurgence of the virus. The majority of cases are linked to type 2 vaccine-derived poliovirus (cVDPV2), responsible for 70 distinct outbreaks in 38 countries. Some regions, particularly in Africa, have experienced persistent transmission lasting over a year, making eradication particularly difficult.

Conflict-affected regions, such as Nigeria and Somalia, have recorded cross-border virus spread, exacerbated by delayed or insufficient vaccination campaigns. This situation highlights the need to strengthen vaccination in vulnerable areas. Enhanced surveillance is crucial to stopping outbreaks before they spread further.

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Final stretch towards eradication?

Circulating vaccine-derived polioviruses continue to threaten public health, especially in areas where vaccination coverage is insufficient. While wild poliovirus has been eradicated in many countries, these variants emerge when vaccine strains mutate after prolonged transmission in under-immunized populations, complicating eradication efforts.

Interrupting their transmission remains a major challenge, especially in regions where vaccination campaigns are hindered by conflicts, limited healthcare access, and vaccine hesitancy. Additionally, the need for frequent booster doses in some areas complicates the sustainable elimination of the virus.

This study aimed to analyze cVDPV outbreaks worldwide and assess the effectiveness of the strategies implemented to curb their spread. The focus is on the impact of vaccination campaigns, the limitations of current vaccines, and new approaches to reducing the emergence of these variants.

The findings highlight that rapid and targeted vaccination is essential to interrupting cVDPV transmission. The introduction of the novel oral polio vaccine type 2 (nOPV2), designed to reduce the risk of mutation, represents a significant advancement. However, its limited distribution, due to production and logistical constraints, remains a major obstacle. Epidemiological surveillance must also be strengthened to quickly detect new strains and limit their spread. Finally, long-term monitoring is necessary to evaluate the effectiveness of nOPV2 and its impact on preventing mutations.

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Scientific reference

Namageyo-Funa, A. (2024). Update on vaccine-derived poliovirus outbreaks—worldwide, January 2023–June 2024. MMWR. Morbidity and Mortality Weekly Report, 73

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