Circulating vaccine derived polio virus type 2 outbreak and response in Yemen, 2021-2022, a retrospective descriptive analysis.

BACKGROUND: The outbreaks of circulating Vaccine Derived Polio Viruses (cVDPVs) have emerged as a major challenge for the final stage of polio eradication. In Yemen, an explosive outbreak of cVDPV2 was reported from August 2021 to December 2022. This study aims to compare the patterns of cVDPV2 outbreak, response measures taken by health authorities, and impacts in southern and northern governorates. METHOD: A retrospective descriptive study of confirmed cases of VDPV2 was performed. The data related to cVDPV2 as well as stool specimens and environmental samples that were shipped to WHO-accredited labs were collected by staff of surveillance. Frequencies and percentages were used to characterize and compare the confirmed cases from the southern and northern governorates. The average delayed time as a difference in days between the date of sample collection and lab confirmation was calculated. RESULTS: The cVDPV2 was isolated from 227 AFP cases reported from 19/23 Yemeni governorates and from 83% (39/47) of environmental samples with an average of 7 months delayed from sample collection. However, the non-polio AFP (NPAFP) and adequate stool specimen rates in the north were 6.7 and 87% compared to 6.4 and 87% in the south, 86% (195) and 14%(32) out of the total 227 confirmed cases were detected from northern and southern governorates, respectively. The first and second cases of genetically linked isolates experienced paralysis onset on 30 August and 1st September 2021. They respectively were from Taiz and Marib governorates ruled by southern authorities that started vaccination campaigns as a response in February 2022. Thus, in contrast to 2021, the detected cases in 2022 from the total cases detected in the south were lower accounting for 22% (7 of 32) of compared to 79% (155 of 195) of the total cases the north. CONCLUSION: A new emerging cVDPV2 was confirmed in Yemen. The result of this study highlighted the impact of vaccination campaigns in containing the cVDPV2 outbreak. Maintaining a high level of immunization coverage and switching to nOPV2 instead of tOPV and mOPV2 in campaigns are recommended and environmental surveillance should be expanded in such a risky country.

Circulating vaccine derived polio virus type 1 outbreak, Saadah governorate, Yemen, 2020.

BACKGROUND: Yemen has faced one of the worst humanitarian crises in the world since the start of the war in 2015. In 2020; 30 Vaccine Derived Polio Virus type 1 (VDPV1) isolates were detected in Saadah governorate. The aims are to characterize the outbreak and address the gaps predisposing the emergence and circulation of VDPV1 in Saadah governorate, Yemen. METHOD: A retrospective descriptive study of confirmed cases of VDPV1 between January and December 2020 was performed. Surveillance staff collected data from patient cases, contacts, as well as stool specimens that shipped to WHO accredited polio labs. Data of population immunity was also reviewed. The difference in days between the date of sample collection, shipment, and receiving lab result was used to calculate the average of delayed days for lab confirmation. RESULTS: From January to December 2020, a total of 114 cases of acute flaccid paralysis (AFP) were reported from 87% (13/15) districts, and cVDPV1 was confirmed among 26% (30) AFP cases. 75% (21) were < 5 years, 73% (20) had zero doses of Oral Polio Vaccine (OPV). The first confirmed case (3%) was from Saadah city, with paralysis onset at the end of January 2020 followed by 5 cases (17%) in March from another four districts, 8 cases (27%) in April, and 13 (43%) up to December 2020 were from the same five districts in addition to 3 (10%) form three new districts. The lab confirmation was received after an average of 126 days (71-196) from sample collection. The isolates differ from the Sabin 1 type by 17- 30 VP1 nucleotides (nt) and were linked to VDPV1 with 13 (nt) divergence that isolated in July 2020 from stool specimens collected before one year from contacts of an inadequate AFP case reported from Sahar district. CONCLUSION: The new emerging VDPV1 was retrospectively confirmed after one year of sample collection from Sahar district. Delayed lab confirmation, as well as the response and low immunization profile of children against polio, were the main predisposing factors for cVDPV1 outbreak. This outbreak highlights the need to maintain regular biweekly shipments to referral polio labs in the short-term, and the exploration of other options in the longer-term to enable the Yemen National Lab to fully process national samples itself.

Diphtheria resurgence in Sada'a-Yemen, 2017-2020.

BACKGROUND: Diphtheria is a contagious vaccine-preventable disease that contributes to the high morbidity and mortality among under 5 children, especially in Yemen. As a consequence of war and collapse of the health system, a fatal epidemic occurred at the end of 2017. This study aims to describe the epidemiology of diphtheria by time, place, and person and vaccination status of affected children. METHODS: A study was conducted in Sada'a governorate by using accumulative line list of diphtheria from November 2017 to September 2020 at electronic Integrated Disease Early Warning System (eIDEWS). The case definition of WHO was adopted. Data was analyzed by Microsoft Excel and Epi info- version 7.2 and multivariable logistic analysis used for identifying significant associated factors. RESULTS: 747 cases were met of WHO case definition. The annual peak of cases started during week 31 and weak 49. Males were slightly more than females (51% vs 49%) and about 35% of cases involved children aged 10 to < 15 years. The overall incidence of diphtheria and case fatality rate (CFR) were 69/ 100,000 and 6.4%, respectively. The highest CFR was among age groups under 5 years 11% (P < 0.001) and among females was 8%. Dysphagia and swollen lymph nodes were the predominant symptoms 98%, 92%, respectively. Based on the Vaccination status, the percentage of unvaccinated and unknown were 53% and 41% respectively, with CFR 11% among cases who received one dose. Furthermore, the most case were from Sahar 40% with case fatality rate 8% and the highest CFR was significantly higher among cases in border and ongoing conflict district (P < 0.05). CONCLUSIONS: The findings highlight that diphtheria is still an ongoing cause of morbidity and mortality among under 5 children in Sada'a that is rising with the low diphtheria immunization coverage. Therefore, concomitant efforts should now focus on improving and monitoring routine immunization across all age groups and healthcare services, especially in borders and continuing conflict districts.

The Acute Flaccid Paralysis (AFP) Surveillance System in Yemen, 2010-2015: Descriptive Study Based on Secondary Data Analysis.

BACKGROUND: Acute flaccid paralysis (AFP) surveillance is an essential strategy for poliovirus eradication. OBJECTIVE: This study aimed to evaluate the performance of the AFP surveillance system in Yemen from 2010 to 2015, identify components that require strengthening, and compare the indicators by year and governorates. METHODS: This descriptive study was based on secondary analysis of AFP surveillance data reported during 2010-2015 from all Yemeni governorates. The World Health Organization (WHO) minimum performance standards were used to evaluate the performance of the AFP surveillance system. RESULTS: A total of 3019 AFP cases were reported between January 2010 and December 2015. At the national level, AFP surveillance achieved WHO targets throughout the evaluating period for the nonpolio AFP rate of cases per 100,000 members of the population younger than 15 years of age, proportion of AFP cases reported within 7 days, proportion of AFP cases investigated within 48 hours of notification, proportion of AFP cases with two adequate stool specimens, and proportion of stool specimens from which nonpolio enterovirus was isolated. However, the proportion of specimens that arrived at the central level within 3 days of the first sample collection and the proportion of stool specimens with results sent from the reference laboratory within 28 days of receipt did not reach targets in 2011 and 2015, respectively. CONCLUSIONS: The AFP surveillance system in Yemen has met most of the WHO indicator levels. Nevertheless, the evaluation showed areas of weakness regarding the arrival of specimens at the central level within 3 days of the first sample collection and delays in processing of the results and submitting feedback by the laboratory. Therefore, there is a need to strengthen the follow-up of specimens submitted to the laboratory.