Progress Toward Rubella and Congenital Rubella Syndrome Control — South-East Asia Region, 2000–2016

Immunization Activities

Before 2000, only two of the 11 SEAR countries (Sri Lanka and Thailand) included RCV in the routine infant immunization schedule. By the end of 2016, eight (73%) countries had introduced RCV (Table 1). India, Indonesia, and North Korea, three countries that include 84% of infants living in the region, had not yet introduced RCV, but India and Indonesia plan to introduce RCV in the immunization schedule in phases during 2017–2019. The age of administration is at age 9–9.5 months for RCV1 and 15–36 months for the second RCV dose (Table 1). WHO and the United Nations Children’s Fund (UNICEF) use reported administrative coverage of RCV1 (i.e., the number of doses administered divided by the estimated target population) along with survey data to estimate national RCV1 coverage (4,5). Estimated regional RCV1 coverage of the birth cohort in the region increased from 3% in 2000 to 15% in 2016 (Figure). Six of eight countries that had introduced RCV1 by 2016 reported ≥90% coverage nationwide (Table 1). During 2000–2016, eight SEAR countries conducted SIAs and vaccinated 83.1 million children, adolescents, and young adults (Table 2).

Surveillance Activities

Rubella cases and outbreaks were reported by three countries (Bhutan, Sri Lanka, and Thailand) in 2000, by nine countries (all but India and Timor-Leste) in 2010, and by all 11 countries in 2013. By 2016, case-based measles-rubella surveillance had been initiated in all SEAR countries and included rubella immunoglobulin M (IgM) antibody testing for all suspected measles cases^§ that tested negative for measles IgM antibody. Countries reported measles-rubella case-based surveillance data indicators^¶ to the WHO SEAR office (6,7). A SEAR measles-rubella laboratory network with eight participating laboratories was established in 2003 as part of the WHO Global Measles and Rubella Laboratory Network. By 2016, the network had expanded to include one regional reference laboratory in Thailand and 39 proficient** national or subnational laboratories (13 in India, four in Indonesia, 14 in Thailand, and one in each of the other eight countries).

The number of SEAR countries reporting CRS cases through the WHO-UNICEF Joint Reporting Form (JRF)^†† increased from two in 2002 to 10 in 2016. North Korea, Sri Lanka, and Thailand report CRS cases as part of the national integrated disease surveillance programs. Eight countries identify CRS cases through sentinel site surveillance (Bangladesh, since 2012; Indonesia and Nepal, 2014; Maldives, 2015; Bhutan, India, Myanmar and Timor-Leste, 2016). Bangladesh also has population-based CRS surveillance, for which all vaccine-preventable disease surveillance reporting sites also report CRS cases.

Rubella Incidence and Rubella Virus Genotypes

From 2010 to 2016, reported annual rubella incidence in SEAR decreased 37%, from 8.6 to 5.4 cases per 1 million population. Five countries reported <1 rubella case per 1 million population in 2016, including four (Bangladesh, Maldives, Sri Lanka, and Thailand) that reported a decrease in incidence of ≥95% since 2010 (Table 1). In 2016, SEAR countries reported 10,361 laboratory confirmed and epidemiologically linked rubella cases, including 1,720 sporadic cases and 8,641 cases that occurred in 263 laboratory-confirmed rubella outbreaks and 68 mixed measles and rubella outbreaks. Only five of the 8,641 confirmed outbreak-associated rubella cases occurred in countries that had introduced RCV. Among the confirmed outbreak-associated cases, 698 (8%) patients were aged <1 year; 2,682 (31%), 1–4 years; 3,297 (38%), 5–9 years; 1,207 (14%), 10–14 years; and 757 (9%), ≥15 years. Overall, 7,884 (91%) of the outbreak-associated cases in 2016 occurred in children aged <15 years. Among all reported rubella cases in 2016, a total of 9,512 (92%) occurred in India and Indonesia (Figure). Reported CRS cases increased from 26 in 2002 to 319 in 2016, reflecting an increase in countries reporting CRS cases from two in 2002 to 10 in 2016 (Table 1). During 2000–2016, 84 rubella viruses (all genotypes 1E or 2B) were reported from the region to the Rubella Nucleotide Sequence Database (RubeNS).^§§

Discussion

Substantial progress was made toward rubella and CRS control in SEAR during 2000–2016, with a 37% decline in reported rubella incidence. Momentum for rubella and CRS control was accelerated by the Regional Committee with the establishment of a regional goal in 2013 to achieve measles elimination and rubella and CRS control by 2020 (1). After this goal was established, countries rapidly introduced RCV, and eight of 11 countries now include RCV in the routine immunization schedule. In four countries (Bangladesh, Maldives, Sri Lanka, and Thailand) rubella and CRS likely have been controlled. Fifteen percent of the SEAR birth cohort received RCV through routine immunization services in 2016; with the introduction of RCV in India and Indonesia beginning in 2017, regional RCV1 coverage is expected to increase rapidly.

In the SEAR countries, rubella cases occurred mostly among children aged <15 years; catch-up SIAs conducted in Bangladesh, Bhutan, Myanmar, Nepal, and Timor-Leste during 2000–2016 targeted this age group and achieved overall decreases in rubella incidence. Therefore, rubella incidence is expected to decrease significantly when the populous countries of India and Indonesia conduct catch-up SIAs as part of RCV introduction into the immunization programs. Periodic high-quality SIAs will be needed to close immunity gaps until high measles and rubella vaccination coverage is achieved through routine immunization services by all countries in the region. Sustained investments to achieve or maintain high routine RCV coverage are needed.

Optimal surveillance for rubella and CRS is essential to monitor the impact of rubella vaccine introduction to ensure that there is no epidemiologic age shift in incidence (from children to women of childbearing age) and to verify progress toward rubella and CRS control goals. As countries progress toward elimination of endemic rubella virus transmission, elimination-standard surveillance will be required (8). Efforts needed to achieve this include modifying the case definition to include all cases of rash and fever from both public and private sector clinical sites and enhancing laboratory capacity to support surveillance, including the ability to process an increased number of specimens following the change to a more sensitive case definition.

The findings in this report are subject to at least two limitations. First, 30%–50% of rubella virus infections are typically asymptomatic or mild; thus many rubella cases are likely not to be detected and reported (2). CRS surveillance complements rubella surveillance data and improves monitoring of rubella disease burden in the population. Second, the quality of surveillance varies among countries, and the definition used for suspected rubella cases varies from country to country, which limits comparisons of surveillance data among countries.

The midterm review of the Strategic Plan for Measles Elimination and Rubella/CRS Control for WHO South-East Asia Region 2014–2020 found evidence that four countries (Bangladesh, Maldives, Sri Lanka, and Thailand) had achieved ≥95% reduction in rubella cases since 2010 (9). The regional goal of rubella and CRS control by 2020 appears to be achievable; with continued investment in high routine RCV coverage, periodic high-quality SIAs, and improved rubella and CRS surveillance, a regional rubella elimination goal might be considered in the near future.