Immunization and Vaccine-Preventable Diseases in the Asia-Pacific Region

Polio Eradication

The commitment to strong routine immunization programs in the 1980s laid the foundation for the Asia-Pacific Region to interrupt the transmission of indigenous wild poliovirus and both WHO Regions to be certified polio-free in 2000 and 2014, respectively; one of the biggest public health achievements. Following the 1988 WHA resolution to eradicate polio globally by the year 2000 (WHA41.28), the Regional Committee of WHO for the Western Pacific in 1988 adopted a resolution to eradicate polio in the Region by 1995 (WPR/RC39.R15).

In 1990, there were an estimated 60,000 polio cases in the WHO Western Pacific Region. By 1995, following concentrated and coordinated country efforts to implement the WHA and Regional Committee decisions, the number of reported polio cases had fallen to 432. The last case of polio due to indigenous wild poliovirus was reported in Cambodia in 1997, and on October 29, 2000, the Western Pacific Regional Commission for Certification of Polio Eradication certified the Region as polio-free.

Since 2000, the Region has successfully maintained its polio-free status by implementing a range of activities, including: (1) increasing and sustaining high routine vaccination coverage with three doses of polio vaccines and addressing immunity gaps (supplementary immunization activities), (2) implementing/strengthening surveillance for poliovirus, (3) implementing annual risk assessments, (4) implementing poliovirus laboratory containment, and (5) effectively responding to outbreaks of imported wild poliovirus (China 2011) and circulating vaccine-derived poliovirus (cVDPV) (Philippines 2001, China 2004, Cambodia 2005, China 2011, China 2012, Lao People’s Democratic Republic 2015–2016, Papua New Guinea 2018, Philippines 2019–2020, and Malaysia 2019–2020). The overall population immunity against poliovirus in the Western Pacific Region is high—25 or more than 70% of the countries officially reported more than 90% coverage with three doses of polio vaccines in 2014–2019.

Sixteen countries using OPV in 2016 switched from trivalent OPV to bivalent OPV from April 17 to May 1, 2016. In 2015–2016, 15 out of 17 eligible countries in the Region had introduced at least one dose of inactivated poliovirus vaccine (IPV) into their national immunization schedules. In addition, three countries/areas (Malaysia, Tokelau, and Tuvalu) stopped using OPV completely and switched to an IPV only schedule in 2015. In September 2018 and in April 2019, Viet Nam and Mongolia introduced one dose of IPV into the national immunization schedule, respectively. Thus, all 17 countries in the Region are using one or more doses of IPV.

Performance of surveillance for polioviruses in the Region was well above the regional threshold for the main indicators during 2014–2019. The indicators for quality of polio surveillance are: nonpolio acute flaccid paralysis (NPAFP) rates are at least 2 cases per 100,000 population under 15 years, >85% of cases have an adequate stool specimen collection rate and 98% of NPAFP cases are investigated within 48 hours of notification. “Adequate” stool specimens are two stool specimens of sufficient quantity for laboratory analysis, collected at least 24 hours apart, within 14 days after the onset of paralysis, and arriving in the laboratory by reverse cold chain and with proper documentation.

A continuous challenge for the WHO Western Pacific Region is multiple outbreaks of cVDPV due to inadroutine immunization levels with OPV coupled with subnational gaps in surveillance in several countries. Recent emergence and circulation of VDPV in the Lao People’s DemRepublic (2015–2016), Papua New Guinea (2018), China (2019), Philippines (2019–2020), and Malaysia (2019–2020) resulted in outbreaks with multiple paralytic cases in some of these countries. The surest way to prevent emergence and circulation of VDPV is to stop the use of OPV in routine immunization schedules.

Less than 30 years before the WHO South-East Asia Region was certified as polio-free in 2014, there were an estimated 250,000 cases occurring each year. Ridding the Region of polio required a new and more flexible approach to public health, combining detailed technical planning, implementation, monitoring, and political advocacy with a focus on reaching high-risk and marginalized populations. Other critical factors included innovation in the way services are delivered, research and product development, effective communication strategies, resource mobilization and coordination with multiple partners.

Regional certification of polio-free status has been maintained, as concluded by the Regional Certification Commission for Polio Eradication during annual meetings. Key strategies are deeply embedded in strong routine immunization and high-quality surveillance systems; with further focus on outbreak preparedness and safely containing polioviruses in facilities where they must be kept for relevant purposes like research and vaccine manufacturing. Countries have subscribed to the Polio Eradication Strategy 2022–2026, noted by the 74th WHA, as the framework until global polio-free certification is achieved. The key components of the strategy are to permanently interrupt all poliovirus transmission in endemic countries, to stop cVDPV transmission and prevent outbreaks in nonendemic countries. Aligned with the Immunization Agenda 2030 and Gavi, the Vaccine Alliance (Gavi) 5.0 strategy, the strategy includes accountability as a key pillar and gender-based objectives and indicators, and it integrates polio functions into broader public health functions.

All countries in the Region have a functional, laboratory supported, NPAFP surveillance system to detect poliovirus transmission. The regional polio laboratory network tested over 87,000 stool specimens in 2019. Environmental surveillance is being conducted through 86 sites in six countries (Bangladesh, India, Indonesia, Myanmar, Nepal, and Thailand). All countries in the Region maintained the certification standard NPAFP rates of at least 1 per 100,000 children under 15 years of age. All but two countries also achieved the operational target of an NPAFP rate ≥2. Adequate stool specimen collection of >80% was reported by eight countries. However, for both performance indicators, there is considerable subnational variance in several countries.

There are 16 polio laboratories in seven countries that perform intra-typic differentiation. Three of these laboratories also perform sequencing. There is one global specialized laboratory and two regional reference laboratories in the Region. Viral isolation results were available for 93.9% of NPAFP cases within 14 days of receipt of samples at the laboratories; all of which achieved the target of 90%. All laboratories are accredited, except one where the status is pending.

IPV is being administered in all countries through routine immunization programs. Four countries in the Region (Bangladesh, India, Nepal, and Sri Lanka) are providing two doses of intradermal IPV. In 2019, seven countries reported IPV coverage greater than 90%, while three achieved coverage of 80–90%. Coverage with three doses of OPV (OPV3) was ≥90% in all but Indonesia.

In 2018–2019, WHO graded outbreaks due to cVDPV type 1 in Indonesia (Papua province) and Myanmar (Kayin State) as emergency grade 1 and immediate response measures were undertaken in the form of large-scale immunization campaigns and NPAFP surveillance strengthening. Indonesia expanded environmental surveillance in Papua and West Papua. Myanmar conducted synchronized immunization activities in cross border areas with Thailand and enhanced NPAFP surveillance. In 2020, the WHO Regional Director for South-East Asia, following recommendations of the virtual outbreak response assessments, declared the closure of the cVDPV type 1 outbreak in Indonesia and in Myanmar.

After type-specific eradication of wild polioviruses and sequential cessation of OPV use, activities are steadily progressing as per the WHO Global Action Plan to minimize poliovirus facility-associated risk (GAPIII). Four poliovirus essential facilities (PEFs) have been identified in the Region (three in India and one Indonesia). All four PEFs designated by their national authorities for containment received the certificate of participation under the GAPIII containment certification scheme from the Global Certification Commission.

Five countries (Bangladesh, India, Indonesia, Myanmar, and Nepal) in the WHO South-East Asia Region established significant polio funded assets (human resource networks, systems, infrastructure, and processes) since 1997 to achieve polio elimination in these countries. All five countries have now developed national polio transition plans to ensure that these assets and capacities continue to support essential polio functions and increasingly contribute to other public health goals.

Many had questioned if poliovirus transmission could ever be stopped in India. Once considered the most difficult place in the world to eliminate wild poliovirus, India achieved this success through a relentless focus on reaching and immunizing every last child with OPV, not once but repeatedly. The success against polio in India was an outcome of committed leadership of the government, dedication of the health workers, tailored strategies, data driven planning through surveillance and research, rigorous monitoring, targeted communication and social mobilization efforts, strong partnerships and adequate funding. An internal accountability framework ensured that all strategies were implemented with the rigor that is required for disease elimination.

WHO played a key role in achieving polio elimination in India since establishing the National Polio Surveillance Project (NPSP) in 1997. The NPSP developed an extensive network of human resources and infrastructure to support the government at the national, state, and sub-state levels. With a network of more than 300 surveillance medical officers (epidemiologists) spread across the entire length and breadth of the country, the project provided support on poliovirus situation assessments, program strategy development, poliovirus surveillance, as well as planning, implementation, and monitoring of supplementary polio immunization activities. While initially focused exclusively on polio eradication, NPSP has gradually expanded its activities to include support for routine immunization, measles and rubella elimination, and multiple other health initiatives.

A solid delivery system for polio immunization campaigns was paired with a strong social mobilization and behavior change strategy. The polio social mobilization network (SMNet) was a crucial component of this. Some 6000 community mobilization coordinators—90% of them female—were recruited from the local communities in the most underserved, marginalized parts of Bihar, Uttar Pradesh, and West Bengal. Each was responsible for 350–500 households. SMNet was a well-managed structure, with 90% of its staff working at the frontline and 10% in three supervisory tiers. Its initial focus was on generating demand for the polio vaccine. This focus later expanded to promote further essential immunization services and other health and sanitation interventions.

After polio virus transmission was stopped, UNICEF transitioned the management and funding of SMNet to the Government of India. SMNet is the legacy of the polio program in India. There is good evidence that SMNet contributed to substantial increases in full immunization coverage. In Bihar, for example, full immunization coverage in the SMNet areas rose from 39% in 2009 to 81% by 2016.

SMNet has been a powerful demonstration of the potential to impact immunization and other behaviors at scale, by systematically applying basic principles: recruitment from the local community; strong supportive supervision; and a multi-pronged strategy that involved (and continues to involve) mass- and mid-media (e.g., posters, brochures and billboards) messaging; information, education and communication materials; ground-level engagement of community influencers and religious leaders, with house-to-house mobilization and mothers meetings; and the use of key community sites such as mosques, schools, and religious festivals to generate demand.

Measles and Rubella Elimination

The seventy-second session of the WHO Regional Committee for South-East Asia in September 2019 adopted the goal of measles and rubella elimination by 2023. This is an update to the previous goal of measles elimination and rubella control by 2020 adopted by the 66th meeting of the Regional Committee in 2013. A costed regional strategic plan for measles and rubella elimination in the WHO South-East Asia Region for the period 2020–2024 was also endorsed by the seventy-second session of the Regional Committee. Measles and rubella elimination is a flagship priority of the Region.

The South-East Asia Regional Verification Commission for Measles and Rubella has verified the elimination of endemic measles in five countries (Bhutan, the Democratic People’s Republic of Korea, Maldives, Sri Lanka, and Timor-Leste). Two countries (Maldives and Sri Lanka) are verified as having eliminated endemic rubella. Another four countries (Bangladesh, Bhutan, Nepal, and Timor-Leste) have sustained rubella and congenital rubella syndrome (CRS) control.

As of December 2019, the WHO South-East Asia Region—home to one fourth of the global population—contained only around 10% of the global burden of reported measles cases compared to 25% in 2018 and 17% of the global burden of reported rubella cases compared to 31% of the global burden in 2018. These data indicate significant progress from previous years. Of the 15 high-burden countries for measles globally, three of them are in the Region—India, Thailand, and Indonesia with rankings of 6, 12, and 14, respectively, globally in 2019. These countries ranked 1, 14, and 11, respectively, in 2018. Similarly, of the 15 high burden countries for rubella globally, two of them are in the Region—India and Indonesia ranking 4 and 5, respectively, in 2019. These countries ranked 2 and 3, respectively, while Bangladesh ranked 14 in 2018.

The Region has achieved a 72% reduction in mortality due to measles in 2018 compared with the corresponding figure for 2000. The reduction in mortality was substantial during the period 2014–2017 (23%). An estimated 97 million children in the Region were reached through supplementary immunization activities in 2017, 199 million reached in 2018 and an additional 205 million reached in 2019.

As of the end of 2019, all countries in the WHO South-East Asia Region were administering two doses of measles containing vaccine (MCV) under their routine immunization program as well as at least one dose of rubella-containing vaccine (RCV). Estimated coverage with the first dose of measles and rubella containing vaccine in 2019 was 94% compared with 63% in 2000. As per the coverage estimates for countries in 2019, seven out of the 11 countries of the Region (Bangladesh, Bhutan, the Democratic People’s Republic of Korea, India, Maldives, Sri Lanka, and Thailand) achieved ≥95% for the first dose MCV (MCV1), while the remaining four (Indonesia, Myanmar, Nepal, and Timor-Leste) reported coverage of 80–94%. While the regional estimated coverage in 2019 was 88% for the second dose MCV (MCV2), four countries (Bangladesh, the Democratic People’s Republic of Korea, Maldives, and Sri Lanka) achieved ≥95% coverage, five countries (Bhutan, India, Myanmar, Thailand, and Timor-Leste) achieved coverage between 80% and 94%, and in two countries (Indonesia and Nepal) the coverage was less than 80%.

All 11 countries initiated case-based surveillance for measles, rubella and CRS and have at least one proficient national laboratory to support measles and rubella case-based surveillance. The measles-rubella laboratory network has expanded from 23 laboratories in 2013 to 50 in 2019 with 41 laboratories accredited as “proficient” for measles and rubella testing.

Measles elimination is estimated to prevent at least 1.1 million cases of measles every year in the Region after elimination is achieved and for every case of measles prevented approximately 2 weeks of disability adjusted life years will be averted. By 2023, approximately 1.1 million deaths due to measles also can be averted through a combination of various strategies during 2020–2023, at an average cost of US$1,373 for each death averted.

Once rubella elimination has been achieved, it is estimated to prevent 52,118 CRS cases annually in the Region. The cost of CRS case management for a single case (treatment and disability support) has been estimated to be US$4200 for low-income countries, US$57,000 per case in middle-income countries, and US$140,000 over a lifetime in high-income countries. The loss of disability adjusted life years for every CRS case averted will be between 27 years in low- and middle-income countries to 18 years in high-income countries.

This flagship area is directly linked to target 3.2 of the Sustainable Development Goals on child mortality as well as target 3.8 on universal access to safe, effective, quality and affordable vaccines for all. This flagship area also contributes to the target of the WHO Thirteenth General Programme of Work to include 1 billion more people in the coverage of essential health services.

In the WHO Western Pacific Region, in 2002, the year prior to the initiation of the regional measles elimination initiative, the measles burden was estimated to be as high as 6.7 million cases and nearly 30,000 deaths. In 2010, approximately 8900 CRS cases were estimated to have occurred due to rubella immunity gaps among adolescents and young adults of child-bearing age.

In 2003, the WHO Regional Committee for the Western Pacific decided to eliminate measles, endorsed the Western Pacific Regional Plan of Action for Measles Elimination and urged Member States to use measles elimination and hepatitis B control strategies to strengthen EPI and other public health programs, such as CRS prevention (WPR/RC54.R3). In 2005, the Regional Committee decided to eliminate measles by 2012 (WPR/RC56.R8). In 2012, the Regional Committee urged Member States to interrupt all residual endemic measles virus transmission as rapidly as possible and further accelerate control of rubella and prevention of CRS through the integration of measles and rubella immunization and surveillance activities (WPR/RC63.R5). In 2014, the Regional Committee endorsed the Regional Framework for Implementation of the GVAP in the Western Pacific (WPR/RC65.R5), which specifies rubella elimination as one of four new regional immunization goals and anticipates development of a detailed strategic plan of action for new goals (WPR/RC65/8).

In 2017, the Regional Committee decided that all Member States in the Region should aim to eliminate rubella as soon as possible and it established a target year for each country or area. The Regional Committee endorsed the Regional Strategy and Plan of Action for Measles and Rubella Elimination in the Western Pacific; and it urged Member States to develop or update national strategies and plans of action relating to measles and rubella elimination and ensure adequate resources are available to implement them (WPR/RC68.R1).

The Regional Strategy and Plan of Action proposed five operational targets toward 2020 for achieving and sustaining measles elimination in the WHO Western Pacific Region: (1) prevent the resurgence of endemic measles virus transmission (genotype B3, D8, D9 and H1), (2) interrupt all ongoing measles transmission in endemic countries, (3) achieve interruption of measles virus transmission in countries and areas approaching measles elimination and sustain measles elimination in countries and areas having reached that target, (4) prevent large-scale outbreaks after importation, and (5) establish and maintain verification-standard measles surveillance supported by WHO-accredited laboratories in all countries and areas of the Region.

The Regional Strategy and Plan of Action also included four operational targets towards 2020 for achieving and sustaining rubella elimination: (1) develop regional verification guidelines by 2018 for rubella elimination, (2) set a national target year for rubella elimination in all countries, (3) develop national strategies and plans of action for rubella elimination in all countries, and (4) establish CRS surveillance in all countries of the Region.

Following historically low incidence of measles and rubella in 2017 and 2018, the year 2019 saw a series of measles and rubella outbreaks in multiple countries of the WHO Western Pacific Region. The successful response to outbreaks in Pacific Island countries (American Samoa, Fiji, Samoa, and Tonga) demonstrated capacity for the Pacific Island subregion to detect imported measles cases and to mount coordinated and capable responses to suspected and confirmed measles cases. Both affected and unaffected countries conducted proactive and comprehensive preparedness activities to prevent uncontrolled spread.

In 2019, 9 out of 16 countries and areas were verified to have achieved and sustained measles elimination (Australia, Brunei Darussalam, Cambodia, Hong Kong SAR [China], Japan, Macao SAR [China], New Zealand, the Republic of Korea, and Singapore). Mongolia was verified in 2014 as having eliminated measles, but following a large and prolonged nation-wide measles outbreak, the Regional Verification Commission determined in 2016 that endemic measles transmission had been re-established there. In the same year, five out of 16 countries and areas were verified as having eliminated rubella (Australia, Brunei Darussalam, Macao SAR [China], New Zealand, and the Republic of Korea). In 2021, Hong Kong SAR (China) achieved rubella elimination.

In 2019–2020, several countries and areas (including Hong Kong SAR [China], Macao SAR [China], the Republic of Korea, and Singapore) were able to prevent prolonged measles transmission despite a very high burden of measles virus importation. China continued to make progress towards measles elimination and had no increase in transmission since 2016 (measles incidence: 18.11 per million population in 2016, 4.31 in 2017, 2.84 in 2018, 2.15 in 2019, and 0.6 in 2020). Genotype data indicate continued absence of H1 genotype in 2020.

As of June 2020, national target dates for rubella elimination were proposed or established in Australia, Japan, Macao SAR (China), Malaysia, New Zealand, the Republic of Korea, Viet Nam, and in the 21 countries and areas of the Pacific Islands epidemiological block.

Maternal and Neonatal Tetanus Elimination

In 1988, WHO estimated that 787,000 newborns died of tetanus. Thus, in the late 1980s, the estimated annual global neonatal tetanus rate was approximately 6.7 per 1000 live births. In 1989, the WHA called for neonatal tetanus elimination (defined as less than one neonatal tetanus case in each district) by 1995 (WHA42.32); in 1990, tetanus elimination was listed as a goal in the World Summit for Children and was again endorsed by the WHA in 1991 (WHA44.33). However, due to slow implementation of the recommended strategies, the target date for elimination was postponed to 2000. In 1999, when progress was reviewed by WHO, UNICEF and the United Nations Population Fund the initiative was reconstituted and elimination of maternal tetanus was added to the goal with a 2005 target date, which was later shifted to 2015. Elimination of maternal tetanus is prevented by the same measures targeting neonatal tetanus; immunization, clean deliveries and cord care practices and surveillance. In 1999, 57 countries had not eliminated MNT. Twelve countries in the Asia-Pacific Region were included on this list.

In May 2016, the validation of MNT elimination in Indonesia following a phased approach like in India led to the achievement of regional MNT elimination in the WHO South-East Asia Region.

Following many years of strong routine immunization and quality surveillance systems it could be assumed that Bhutan, the Democratic People’s Republic of Korea, Maldives, Sri Lanka, and Thailand had already achieved MNT elimination before 2000. Validation exercises in Bangladesh, India, Myanmar, Nepal, and Timor-Leste in the period 2000–2015 confirmed those countries reached the goal as well. As such, all countries contributed to the South-East Asia Region being the second WHO Region to achieve this public health milestone.

India, as federal union comprising 28 states and 8 union territories, approached MNT elimination in a phased manner and on April 15, 2015, WHO confirmed that India had successfully eliminated MNT. This landmark achievement was the conclusion of an in-depth data review and community-based validation surveys, the last of which was conducted in Nagaland.

Recognizing the high neonatal tetanus burden in the country, estimated at 150,000–200,000 cases annually, India committed itself to achieve MNT elimination through strengthening of routine immunization activities, including tetanus toxoid vaccine coverage, and improving clean delivery practices through institutional births and training of birth attendants. The launch of the National Rural Health Mission in 2005 helped strengthening these initiatives. Strategies to improve clean delivery included the innovative Janani Suraksha Yojana , a conditional cash transfer scheme, to encourage women to give birth in a health facility. The interventions to improve tetanus toxoid coverage and reduce MNT mortality under the National Rural Health Mission included health systems strengthening and behavior change communication to increase demand for quality service. Outreach services were integrated and extended through village health and nutrition days including vaccination of children, adolescents and pregnant women with tetanus toxoid vaccines. Operationalization of subcenters and community health centers led to providing obstetric and neonatal care services 24 hours a day and seven days a week. Engagement of more than 900,000 accredited social health activists generated demand and facilitated the use of health-care services by communities and poor women. This was complemented by the promotion of institutional deliveries focusing on disadvantaged pregnant women, including an institutional stay for 48 hours and the introduction of the “Dial 108” ambulance system, to address the need for emergency transport.

Indonesia likewise pursued MNT elimination validation in a phased manner; with regions 1 (Java, Bali) and 2 (Sumatera) and region 3 (Kalimantan, Sulawesi, Nusa Tenggara Timur, and Barat) achieving the goal in 2010 and 2011, respectively. The three regions already counted for 88.7% of the cities or districts of Indonesia and 97.4% of the Indonesian population. On 19 May 2016 the last region of the country (Maluku, Papua, Papua Barat) achieved validation, following extensive data review and field surveys in Papua, which was considered the lowest performing province (3rd administrative level). The WHO-led assessment team concluded that MNT elimination has been achieved in Papua and by extension in Indonesia as a whole. The success in Indonesia was based on a combination of providing routine tetanus toxoid containing vaccines to immunize pregnant women and “brides-to-be,” school-based immunization as well as targeted supplemental immunization of all women of childbearing age in areas considered high risk for neonatal tetanus, and also by ensuring clean and safe deliveries.

In 2014, the Regional Committee of the Western Pacific endorsed the Regional Framework for Implementation of the Global Vaccine Action Plan in the Western Pacific (WPR/RC65.R5), which specifies MNT elimination as one of eight immunization goals for the Region. MNT targets included: (1) achieve MNT elimination (defined as <1 neonatal tetanus case per 1,000 live births in each district) by 2015, and (2) maintain MNT elimination in every country and area. As of 2020, five countries of the Region were validated as having achieved MNT elimination: Viet Nam in 2005, China in 2012, Lao People’s Democratic Republic in 2013, Cambodia in 2015, and Philippines in 2017. Only Papua New Guinea has yet to achieve MNT elimination in the WHO Western Pacific Region.

Eliminating MNT—and maintaining elimination status—requires investment in health systems, human resources, and infrastructure logistics to deliver immunization and maternal health services to everyone in a target population. At the country level, providing services to underserved, remote, and marginalized populations is a positive sign of political will and the ability to deliver health for all. The cost of immunization with tetanus toxoid is as little as $0.05–$0.20 per dose, helping to avert substantial health risks for mothers and newborns and providing a compelling case to ministries of finance to invest in preventing tetanus infection. Eliminating MNT is cost-effective, equity-oriented, and integrated within the health system. It also aims for sustainability, in line with universal health coverage and the health-related Sustainable Development Goals.

Elimination has a direct benefit to the national economy through the increased economic activity of women in particular if they are freed from the fatal risk of maternal tetanus. A study published in 2017 showed that by 2016 a total of at least US$1 billion would have been contributed to the global economy in the form of additional labor productivity due to a reduction in deaths from maternal tetanus. The same study demonstrated that investing in reducing and ultimately eliminating MNT produces a return on investment of US$7 to household economies for every US$1 invested. This represents a substantial investment in the economic well-being of future generations.