Update on Wild Poliovirus Type 1 Outbreak — Southeastern Africa, 2021–2022

Abstract

Polio SIAs are mass immunization campaigns intended to interrupt poliovirus circulation, usually by immunizing every child aged <5 years with 2 oral polio vaccine doses, regardless of previous immunization status.

Progress Toward Poliomyelitis Eradication — Worldwide, January 2021–March 2023

“…During January 1, 2021–March 31, 2023, GPEI supported 48 countries in implementing 219 SIAs, during which approximately 988 million bOPV, 616,000 IPV, 960,000 fractional IPV, 90 million mOPV2, 595 million nOPV2, and 100 million tOPV doses were administered. In 2022, lot quality assurance sampling (LQAS) ¶ surveys after SIAs indicated performance gaps in high-risk districts in Afghanistan, Malawi, Mozambique, and Pakistan ( 8 – 10 ).…”

“…In 2021, a single paralytic WPV1 case in Malawi was genetically linked to virus circulating in Pakistan and was confirmed in February 2022. In 2022, eight WPV1 cases were detected in Mozambique, genetically linked to the Malawi case, with the latest date of paralysis in August 2022 ( 10 ).…”

The Fight against Poliovirus Is Not Over

“…In 2021, five cases of WPV1 were reported in these two countries, which represents a significant decrease compared to the previous year. One case of WPV1 was also reported in Namibia (non-endemic country) [ 6 ]. In 2022, 2 cases of WPV1 were reported in Afghanistan, 20 in Pakistan and 8 cases in Mozambique (non-endemic country) ( Figure 2 b) [ 6 ].…”

“…One case of WPV1 was also reported in Namibia (non-endemic country) [ 6 ]. In 2022, 2 cases of WPV1 were reported in Afghanistan, 20 in Pakistan and 8 cases in Mozambique (non-endemic country) ( Figure 2 b) [ 6 ]. Only one case of WPV1 was reported in Pakistan between January 2023 and May 2023 [ 62 ].…”

“…However, the endemic transmission of WPV1 persists in Afghanistan and Pakistan in 2022 [ 5 ]. Nine cases of paralytic polio caused by WPV1 in children and adolescents were reported in Southeast Africa between November 2021 and December 2022, including one case in Malawi and eight cases in Mozambique [ 6 ]. The oral poliovirus vaccine (OPV) has protected millions of children from paralysis by preventing person-to-person transmission of the virus, which is essential for polio eradication [ 7 ].…”