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Toizumi M, Takamatsu M, Toda K, Horikoshi Y. Progresses Toward Polio Eradication in Asian Countries: Its History and Japan's Contributions. Pediatr Infect Dis J 2024:00006454-990000000-00950. [PMID: 39037255 DOI: 10.1097/inf.0000000000004478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
Japan experienced a large outbreak of wild poliovirus in the 1960s. The government made an exceptional decision to import oral polio vaccines (OPVs) from the Soviet Union and Canada while bypassing the usual approval process for medical products. Mass vaccination and subsequent, routine immunization successfully contained the wild poliovirus; the last case in Japan was reported in 1980. Domestic OPV had been used to sustain Japan's polio-free state. In 2012, the world's first inactivated polio vaccine developed from the Sabin vaccine replaced OPVs. Domestic vaccines combined with Sabin-derived inactivated polio vaccine are currently used in Japan. When the World Health Assembly announced the Global Polio Eradication Initiative in 1988, the Japanese government made a commitment to support endemic countries. The Japan International Cooperation Agency supported the establishment of microbiological laboratories, surveillance, distribution of polio vaccines and capacity building. Vaccine-derived poliovirus emerged as a new, international risk in the early 2000s. Vaccine-derived poliovirus was also detected in several Asian countries and required an outbreak response with additional vaccinations and strengthened surveillance. Genetically stable, novel, oral polio vaccine type 2 became available for use in outbreak responses and was used in Indonesia. Japan maintains its commitment to work toward the eradication of the poliovirus.
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Affiliation(s)
- Michiko Toizumi
- From the Department of Pediatric Infectious Diseases, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Masamitsu Takamatsu
- World Health Organization Papua New Guinea, Port Moresby, Papua New Guinea
- Health and Global Policy Institute, Tokyo, Japan
| | - Kohei Toda
- Immunization Center, Akita Red Cross Hospital, Akita, Japan
| | - Yuho Horikoshi
- Division of Infectious Diseases, Department of Pediatrics, Tokyo Metropolitan Children's Medical Center, Tokyo, Japan
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Yin Q, Zheng Y, Ying Z, Li J, Jiang Y, Bao W, Dou Y, Pu Y, Lei J, Yang H, Jiang R, Deng Y, Zhao Z, Pu J, Yang J, Li Y, Xu M, Cai W, Che Y, Shi L. Immunogenicity and lot-to-lot consistency of booster shot with Sabin inactivated poliomyelitis vaccine in Chinese children aged 18-24 Months: A phase Ⅳ clinical trial. Vaccine 2024; 42:1973-1979. [PMID: 38388236 DOI: 10.1016/j.vaccine.2024.02.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 02/11/2024] [Accepted: 02/12/2024] [Indexed: 02/24/2024]
Abstract
BACKGROUND There has been no data on the immunogenicity and safety of the 4th booster dose of the sIPV immunization in 18-24 months old children in post-marketing studies of large cohort providing with robust results. METHOD In a phase Ⅳ randomized, double-blinded clinical trial, 1200 participants aged 2 months were immunized with three consecutive doses of sIPV at 2, 3, and 4 months old to complete primary immunization. Out of the 1200 participants, 1129 received the 4th dose of sIPV as booster immunization. Immunogenicity was evaluated in 1100 participants. RESULTS Seropositive rates of the anti-poliovirus type 1, 2, and 3 neutralizing antibodies were 99.9 %, 98.0 %, 98.2 %, respectively, with GMTs of 557.0, 146.1, 362.0 one year after primary vaccination. After booster vaccination between 18 and 24 months old, the seropositive rates for 3 types all reached 100.0 %, with GMTs of 8343.6, 5039.6, 5492.0, respectively. Particularly for the anti-poliovirus type 2 antibody, the GMT was 230.4 after primary immunization, maintained to 146.1 one year after primary immunization, and increased to as high as 5039.6 after booster vaccination. The GMT ratios between each batch groups after booster immunization were between 0.67 and 1.50, meeting the immunological equivalence criteria. The incidence rate of adverse reaction was 23.0 %, which was comparable to those in the phase Ⅲ trial but had a lower incidence. Furthermore, no SUSAR was reported in this study. INTERPRETATION In conclusion, as the anti-poliovirus antibodies gradually waned one year post sIPV primary vaccination, especially the type 2 antibody waned to a very low level, suggesting the importance of the booster immunization for children at the age of 18-24 months old. The booster shot can greatly enhance the antibody level and protect children from the potential risk of infection with WPV and VDPV by supplementing the anti-poliovirus type 2 immunity gap in the current real world. Clinic Trial Registration. NCT04224519.
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Affiliation(s)
- Qiongzhou Yin
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China
| | - Yan Zheng
- Vaccine Clinical Research Center, Yunnan Center for Disease Control and Prevention, Kunming, Yunnan, China
| | - Zhifang Ying
- Division of Respiratory Virus Vaccines, National Institutes for Food and Drug Control, Beijing, China
| | - Jingyu Li
- Vaccine Clinical Research Center, Yunnan Center for Disease Control and Prevention, Kunming, Yunnan, China
| | - Ya Jiang
- Mile Center for Disease Control and Prevention, Mile, Yunnan, China
| | - Wenmei Bao
- Gejiu Center for Disease Control and Prevention, Gejiu, Yunnan, China
| | - Youjian Dou
- Mile Center for Disease Control and Prevention, Mile, Yunnan, China
| | - Yi Pu
- Gejiu Center for Disease Control and Prevention, Gejiu, Yunnan, China
| | - Jin Lei
- Gejiu Center for Disease Control and Prevention, Gejiu, Yunnan, China
| | - Haitao Yang
- Vaccine Clinical Research Center, Yunnan Center for Disease Control and Prevention, Kunming, Yunnan, China
| | - Ruiju Jiang
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China
| | - Yan Deng
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China
| | - Zhimei Zhao
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China
| | - Jing Pu
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China
| | - Jing Yang
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China
| | - Yadong Li
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China
| | - Min Xu
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China
| | - Wei Cai
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China
| | - Yanchun Che
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China.
| | - Li Shi
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming, Yunnan, China.
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Guo Q, Zhu S, Wang D, Li X, Zhu H, Song Y, Liu X, Xiao F, Zhao H, Lu H, Xiao J, Yu L, Wang W, He Y, Liu Y, Li J, Zhang Y, Xu W, Yan D. Genetic characterization and molecular evolution of type 3 vaccine-derived polioviruses from an immunodeficient patient in China. Virus Res 2023; 334:199177. [PMID: 37479187 PMCID: PMC10388201 DOI: 10.1016/j.virusres.2023.199177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 07/06/2023] [Accepted: 07/18/2023] [Indexed: 07/23/2023]
Abstract
In 2013, a case of immunodeficiency vaccine-derived poliovirus (iVDPV) was identified in Jiangxi Province, China. In this study, we purified 14 type 3 original viral isolates from this case and characterized the molecular evolution of these iVDPVs for 298 days. Genetic variants were found in most of the original viral isolates, with complex genetic and evolutionary relationships among the variants. A phylogenetic tree constructed based on the P1 region showed that these iVDPVs were classified into lineage A and B. The dominant lineage B represents a major trend in virus evolution. The nucleotide substitution rate at the third codon position (3CP) estimated by the BEAST program was 1.76 × 10-2 substitutions/site/year (95% HPD: 1.23-2.39 × 10-2). The initial OPV dose was given dating back to March 2013, which was close to the time of the last OPV vaccination, suggesting that OPV infection may have originated with the last dose of vaccine. Recombinant analysis showed that these iVDPVs were inter-vaccine recombinants with two recombination patterns, S3/S2/S1 and S3/S2/S3/S2/S1. Whole genome sequence analysis revealed that key nucleotide sites (C472U, C2034U, U2493C) associated with the attenuated phenotype of Sabin 3 have been replaced. Temperature sensitivity test showed that all tested strains were temperature-sensitive, except for the variant Day11-5. Interestingly, we observed that the variant Day11-5 temperature resistance properties may be associated with the Lys to Met substitution at the VP2-162 site. Serological test and whole genome sequence analysis showed that the seropositivity rate remained high, and mutations in the antigenic sites did not significantly alter neutralization ability.
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Affiliation(s)
- Qin Guo
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China; Da Zhou Vocational College of Chinese Medicine, Dazhou, China
| | - Shuangli Zhu
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Dongyan Wang
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Xiaolei Li
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Hui Zhu
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Yang Song
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Xiaoqing Liu
- Jiangxi Center for Disease Control and Prevention, Nanchang, China
| | - Fang Xiao
- Jiangxi Center for Disease Control and Prevention, Nanchang, China
| | - Hehe Zhao
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Huanhuan Lu
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Jinbo Xiao
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Liheng Yu
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Wenhui Wang
- School of Public Health and Management, Shandong First Medical University, Shandong Academy of Medical Sciences, Jinan, China
| | - Yun He
- School of Public Health and Management, Shandong First Medical University, Shandong Academy of Medical Sciences, Jinan, China
| | - Ying Liu
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Jichen Li
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Yong Zhang
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Wenbo Xu
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China
| | - Dongmei Yan
- National Polio Laboratory, WHO WPRO Regional Polio Reference Laboratory, National Health Commission Key Laboratory for Biosecurity, National Health Commission Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention Beijing, China.
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Zhang M, Yang J, Bai Y, Zhu H, Wang C, Zhang L, Xu J, Lu M, Zhang X, Xiao Z, Ma Y, Wang Y, Li X, Wang D, Zhu S, Yan D, Xu W, Zhang Y, Zhang Y. Epidemiological survey and genetic characterization of type 3 vaccine-derived poliovirus isolated from a patient with four doses of inactivated polio vaccine in Henan Province, China. Infect Dis Poverty 2022; 11:124. [PMID: 36514167 DOI: 10.1186/s40249-022-01028-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 09/13/2022] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Vaccine-derived poliovirus (VDPV) is a potential threat to polio eradication because they can reintroduce into the general population and cause paralytic polio outbreaks, a phenomenon that has recently emerged as a prominent public health concern at the end of global polio eradication. This study aimed to describe the epidemiology and genetic characteristics of the first VDPV identified from a patient with acute flaccid paralysis (AFP), with four doses of inactivated polio vaccine immunization in Henan Province, China in 2017. METHODS The patient was diagnosed with type 3 VDPV. Subsequently, a series of epidemiological approaches was implemented, including a retrospective search of AFP cases, rate of vaccination assessment, study of contacts, and supplementary immunization activities. Fecal samples were collected, viral isolation was performed, and the viral isolates were characterized using full-length genomic sequencing and bioinformatic analysis. RESULTS Phylogenetic analysis showed that the viral isolates from the patient were different from other reported genetic clusters of type 3 VDPV worldwide. They were identified as a Sabin 3/Sabin 1 recombinant VDPV with a crossover site in the P2 region. Nucleotide substitutions, including U → C (472) and C → U (2493), have been identified, both of which are frequently observed as reversion mutations in neurovirulent type 3 poliovirus. A unique aspect of this case is that the patient had been vaccinated with four doses of inactive polio vaccine, and the serum neutralizing antibody for Sabin types 1 and 3 were 1∶16 and 1∶512, respectively. Thus, the patient was speculated to have been infected with type 3 VDPV, and the virus continued to replicate and be excreted for at least 41 d. CONCLUSIONS The existence of this kind of virus in human population is a serious risk and poses a severe challenge in maintaining a polio-free status in China. To the best of our knowledge, this is the first report of VDPV identified in the Henan province of China. Our results highlight the importance of maintaining a high-level vaccination rate and highly sensitive AFP case surveillance system in intercepting VDPV transmission.
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Affiliation(s)
- Mingyu Zhang
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Jianhui Yang
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Yiran Bai
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Hui Zhu
- WHO WPRO Regional Polio Reference Laboratory and National Health Commission Key Laboratory for Biosafety, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China
| | - Changshuang Wang
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Lu Zhang
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Jin Xu
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Mingxia Lu
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Xiaoxiao Zhang
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Zhanpei Xiao
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Yating Ma
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Yan Wang
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China
| | - Xiaolei Li
- WHO WPRO Regional Polio Reference Laboratory and National Health Commission Key Laboratory for Biosafety, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China
| | - Dongyan Wang
- WHO WPRO Regional Polio Reference Laboratory and National Health Commission Key Laboratory for Biosafety, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China
| | - Shuangli Zhu
- WHO WPRO Regional Polio Reference Laboratory and National Health Commission Key Laboratory for Biosafety, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China
| | - Dongmei Yan
- WHO WPRO Regional Polio Reference Laboratory and National Health Commission Key Laboratory for Biosafety, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China
| | - Wenbo Xu
- WHO WPRO Regional Polio Reference Laboratory and National Health Commission Key Laboratory for Biosafety, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.,Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, People's Republic of China
| | - Yong Zhang
- WHO WPRO Regional Polio Reference Laboratory and National Health Commission Key Laboratory for Biosafety, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China. .,Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, People's Republic of China.
| | - Yanyang Zhang
- Henan Center for Disease Control and Prevention, Zhengzhou, Henan, People's Republic of China.
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Xu Y, Liu Y, Wang J, Che X, Du J, Zhang X, Gu W, Zhang X, Jiang W. Cost-effectiveness of various immunization schedules with inactivated Sabin strain polio vaccine in Hangzhou, China. Front Public Health 2022; 10:990042. [PMID: 36211670 PMCID: PMC9545176 DOI: 10.3389/fpubh.2022.990042] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Accepted: 08/24/2022] [Indexed: 01/26/2023] Open
Abstract
Background It is necessary to select suitable inactivated poliovirus vaccine(IPV) and live, attenuated oral poliovirus vaccine (OPV) sequential immunization programs and configure the corresponding health resources. An economic evaluation was conducted on the sequential procedures of Sabin strain-based IPV (sIPV) and bivalent OPV (bOPV) with different doses to verify whether a cost-effectiveness target can be achieved. This study aimed to evaluate the cost-effectiveness of different sIPV immunization schedules, which would provide convincing evidence to further change the poliovirus vaccine (PV) immunization strategies in China. Methods Five strategies were included in this analysis. Based on Strategy 0(S0), the incremental cost (IC), incremental effect (IE), and incremental cost-effectiveness ratio (ICER) of the four different strategies (S1/S2/S3/S4) were calculated based on the perspective of the society. Seven cost items were included in this study. Results of field investigations and expert consultations were used to calculate these costs. Results The ICs of S1/S2/S3/S4 was Chinese Yuan (CNY) 30.77, 68.58, 103.82, and 219.82 million, respectively. The IE of vaccine-associated paralytic poliomyelitis (IEVAPP) cases of S1/S2/S3/S4 were 0.22, 0.22, 0.22, and 0.11, respectively, while the IE of disability-adjusted life-years (IEDALY) of S1/S2/S3/S4 were 8.98, 8.98, 8.98, and 4.49, respectively. The ICERVAPP of S1/S2/S3/S4 gradually increased to CNY 13.99, 31.17, 47.19, and 199.83 million/VAPP, respectively. The ICERDALY of S1/S2/S3/S4 also gradually increased to CNY 0.34, 0.76, 1.16, and 4.90 million/DALY, respectively. Conclusion ICERVAPP and ICERDALY were substantially higher for S3 (four-sIPV) and S4 (replacement of self-funded sIPV based on one-sIPV-three-bOPV). Two-sIPV-two-bOPV had a cost-effectiveness advantage, whereas S2/S3/S4 had no cost-effectiveness advantage.
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Kitamura K, Shimizu H. Outbreaks of Circulating Vaccine-derived Poliovirus in the World Health Organization Western Pacific Region, 2000-2021. Jpn J Infect Dis 2022; 75:431-444. [PMID: 36047174 DOI: 10.7883/yoken.jjid.2022.312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The World Health Organization Western Pacific Region (WPR) has maintained the polio-free status for more than two decades. At the global level, there were only 6 confirmed polio cases due to wild type 1 poliovirus in Pakistan, Afghanistan, and Malawi in 2021, therefore, the risk of the importation of wild poliovirus from the endemic countries to the WPR is considerably lower than ever before. On the other hand, the risk of polio outbreaks associated with circulating vaccine-derived polioviruses (cVDPVs) still cannot be ignored even in the WPR. Since late 2010s, cVDPV outbreaks in the WPR have appeared to be more extensive in frequency and magnitude. Moreover, the emergence of concomitant polio outbreaks of type 1 and type 2 cVDPVs in the Philippines and Malaysia during 2019-2020 has highlighted the remaining risk of cVDPV outbreaks in high-risk areas and/or communities in the WPR. The previous cVDPV outbreaks in the WPR have been rapidly and effectively controlled, however, the future risk of polio outbreaks associated with cVDPVs needs to be reconsidered and polio immunization and surveillance strategies should be updated accordingly.
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Affiliation(s)
- Kouichi Kitamura
- Department of Virology II, National Institute of Infectious Diseases, Japan
| | - Hiroyuki Shimizu
- Department of Virology II, National Institute of Infectious Diseases, Japan
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