Expanded programme on immunization

Seventh Meeting of Vaccine-Preventable Diseases Laboratory Networks in the Western Pacific Region

The Seventh Meeting of Vaccine-Preventable Diseases Laboratory Networks in the Western Pacific Region was held in Manila, Philippines from 26 to 29 September 2017, to review the performance and identify the challenges of the poliovirus and measles and rubella network laboratories in the Region. The meeting reviewed ways to further strengthen the performance of network laboratories and also to monitor the implementation of recommendations from the sixth Vaccine-Preventable Diseases Laboratory Networks meeting in September 2016. This seventh meeting provided an opportunity to discuss strengthening the quality and sensitivity of poliovirus detection, enhancing poliovirus surveillance through the introduction of environmental surveillance (ES) in key countries and applying the global action plan for the containment of poliovirus in the laboratory network. Ways to improve the quality and timeliness of laboratory-based surveillance, the challenges of identifying funds for the procurement and delivery of high-quality laboratory supplies, the importance of improving molecular surveillance for support of verification of elimination of measles and rubella, and the strengthening of rubella and congenital rubella syndrome (CRS) surveillance were also discussed.

Polio laboratory network

A two-day series of 11 sessions for the polio laboratory network in the Western Pacific Region was organized to discuss global progress towards polio eradication, to identify challenges in maintaining polio-free status in the Western Pacific Region, to share updates on global and regional polio laboratory networks, to review the performances of the polio network laboratories and to discuss the implementation of new polio containment requirements following the implementation of GAPIII. The sessions included updates on the global transmission of wild and vaccine-derived polioviruses, new methods and perspectives which included direct detection of polioviruses, next-generation sequencing, possible alternatives to microneutralization assays for immunity assessments and a review of the new enhanced intratypic differentiation (ITD) techniques introduced in the past 12 months. Laboratory containment and the implementation of the WHO global action plan to minimize inadvertent release of polioviruses, quality assurance, detection of polioviruses from ES, post-certification planning, data management and country reports completed the extent of the sessions covered.

The meeting concluded that the performance of the regional polio laboratory network has been sustained at polio-free-certification standard and that acute flaccid paralysis (AFP) surveillance activities have been efficiently supported. The network laboratories provided critical evidence in support of the continued polio-free status of the Region. As of August 2017, all 43 network laboratories are accredited including all 38 polio laboratories with ITD function. Of the five virus- isolation-only laboratories, three will undergo ITD accreditation in the near future. A total of 42 laboratories tested and passed the virus isolation proficiency test (PT) in 2016 with a 100% score; however, two laboratories required a second attempt after an initial failure. Forty-one laboratories performed the 2016 ITD/VDPV PT in January 2017. A total of 29 laboratories passed the first attempt; however, eight of the 12 that did not pass achieved 100% on the second attempt. Four laboratories are pending due to delays in shipment of new panels. Two of the seven laboratories performing the sequencing PT did not reach the passing score but did so on repeat testing. All laboratories that did not pass their initial PTs have been provided with extensive support to strengthen their capability.

Since the Western Pacific Region has been polio-free for more than 10 years, 43 network laboratories (12 national and 31 China provincial) have been actively involved in supplementary enterovirus or ES. China established an extensive hand-food-and-mouth disease (HFMD) laboratory network based on existing polio laboratories, and Japan and Viet Nam have also implemented HFMD surveillance. The polio laboratories in Australia, China, Japan, Malaysia, the Philippines and Singapore are involved in testing samples collected from ES in the Region in 2016 and 2017 with Viet Nam investigating the introduction of environmental surveillance by the end of 2017. A total of 7028 AFP cases with specimens were tested in the Region in 2016 and 3849 were tested in 2017 (as of 13 September). The Lao People’s Democratic Republic detected the most recent circulating vaccine-derived poliovirus (cVDPV) cases during late 2015 and early 2016. No cases have been detected since January 2016. China identified two VDPVs in AFP cases, one in 2016 and one in 2017, both of which were determined to be “ambiguous”. None showed spread after extensive investigation. After the switch from trivalent oral polio vaccine (tOPV) to bivalent oral polio vaccine (bOPV) in April 2016, Sabin type 1 and 3 viruses are being isolated from both AFP cases and environmental samples. In the case of Sabin type 2, the last isolation was from environmental samples in China in August 2016. Starting from September 2016, there are no Sabin type 2 viruses isolated either from AFP cases or environmental samples. The continued use of ES and enterovirus surveillance in a number of countries and areas in the Region has provided valuable data to support evidence of the continued polio-free status of the Region.

The preparation for implementation of GAPIII is progressing in the Region and Phase 1a containment for wild poliovirus type 2 (WPV2) and vaccine-derived poliovirus type 2 (VDPV2) has been completed. Biorisk management training for polio essential facilities (PEFs) and for national authorities of containment (NACs) was carried out in 2015 and 2016, and an auditors’ training for the Containment Certification Scheme (CCS) occurred in 2017 with training in local languages (Chinese, Japanese and Vietnamese). Strong advocacy from the WHO Regional Office for the Western Pacific and commitment from countries have resulted in a reduced number of laboratories identifying themselves as potential PEFs. Currently, five countries (Australia, China, Japan, Republic of Korea and Viet Nam) have identified that they will establish a total of 16 PEFs.

Considerable efforts have been made to achieve polio eradication in the Region with a critical contribution from the polio laboratory network. Continuous strong quality assurance procedures and development of new technologies to enhance the sensitivity of detecting wild and vaccine-derived polioviruses are being implemented in the Region, ensuring high-performance, high-quality laboratory support.

Measles and rubella laboratory network

A two-day series of 12 sessions for the regional measles and rubella laboratory network was organized to review progress, identify challenges and develop plans to further strengthen the performance of network laboratories in support of measles and rubella elimination. The sessions included presentations on global and regional updates on progress with measles and rubella elimination, strengthening the coordination and cooperation between laboratory and epidemiology surveillance, the laboratories’ role in the verification process for the elimination of measles and rubella, strengthening rubella and CRS surveillance, new perspectives and technologies, quality assurance, data management, country reports, and the impact of polio transition and polio containment on the MR LabNet.

The meeting concluded that measles and rubella network laboratories have greatly contributed to the regional goal of measles and rubella elimination through the timely and accurate confirmation of suspected cases and identifying measles and rubella virus genotypes circulating in the Region. The laboratory network has played a critical role in the recent verification of measles elimination of eight Member States by providing evidence that measles cases found in these countries are imported rather than due to endemic circulation. The network consists of a total of 386 laboratories: one global specialized laboratory (GSL) in Japan, three regional reference laboratories (RRLs) in Australia, China and Hong Kong SAR (China), 17 national measles and rubella laboratories, 31 provincial and 331 prefectural laboratories in China, and three subnational laboratories in Malaysia (N=1) and Viet Nam (N=2). Singapore has recently changed their national laboratory from the Singapore General Hospital to the National Public Health Laboratory. A total of 10 laboratories were assessed under the WHO accreditation process following on-site reviews with desk reviews now taking precedence to reduce the workload of the Regional Laboratory Coordinator (RLC).

The role of molecular surveillance for confirming and maintaining verification of measles and rubella elimination is increasingly crucial for the laboratory network. Countries are encouraged to collect samples for sequencing and genotyping for at least 80% of chains of infection for measles and especially rubella, but gaps still exist. Genotype and sequence information for measles submitted to the Measles Nucleotide Surveillance (MeaNS) WHO sequence database for measles was received from 12 countries. For rubella, sequences were submitted to the Rubella Nucleotide Surveillance (RubeNS) genotype database for five countries in the Region. The RRL in Hong Kong SAR (China) greatly contributed to the regional measles and rubella genotype databases by sequencing serum samples from six countries that sent samples for confirmatory testing.

All 54 laboratories in the Region that participated in the annual global serology quality assurance (QA) programme passed in 2016 and 13 of the 13 laboratories passed the molecular QA PT except for one result still pending for measles. Confirmatory testing samples were sent from 10 of 17 national laboratories in 2016 with all 10 laboratories achieving greater than 90% concordance for measles Immunoglobulin M results and nine for rubella.

Establishing CRS surveillance in countries in the Region continues to be a challenge. No country is sharing case-based CRS data with the WHO Regional Office for the Western Pacific yet. Surveillance officers from key countries shared their experiences in building linkages with their laboratory colleagues and thereby facilitating a more comprehensive surveillance programme for rubella/CRS and also measles.

The regional measles and rubella laboratory network has made considerable progress since establishment began in 1998. The network laboratories all follow WHO-recommended methods and procedures under a strong environment of quality assurance. A total of 141 000 serum samples from suspected measles and rubella cases were reported in 2016 were reported timely and accurately. The high capacity of molecular detection in most laboratories in the Region has resulted in 3058 measles virus sequences and 102 rubella sequences being reported to the WHO genotype databases in 2016, allowing informed decisions on the molecular surveillance of measles and rubella globally and in the Region and contributing to the verification status of countries.