Rubella in the Western Pacific, 2000–2019: Coverage Reached 96%, Then Outbreaks Returned

Rubella is the leading vaccine-preventable cause of birth defects. Usually a mild fever-and-rash illness, it can cause miscarriage, fetal death or congenital rubella syndrome (CRS) — often vision, hearing or heart defects — when a woman is infected during pregnancy, especially in the first trimester.

The World Health Organization's Western Pacific Region covers 37 countries and areas and about 1.9 billion people, from China, Japan and the Philippines to Australia and the Pacific islands. In 2012 its Regional Committee committed to faster rubella control, and in 2017 resolved that every country should aim for elimination — no endemic transmission for at least 12 months with good surveillance — as soon as possible. Countries build on measles elimination work: a combined measles-rubella vaccine, fever-and-rash surveillance and joint lab testing.

Key findings, 2000–2019

• All 37 countries and areas now include rubella vaccine in infant immunization, and nearly all give two doses.
• Coverage with a first dose rose from 11% in 2000 to 96% in 2019 — 90% or more since 2015, after China (2007) and Vietnam (2015) introduced the vaccine and reached high coverage.
• About 84.3 million people were vaccinated in 62 campaigns in 27 countries from 1970 to 2019.
• Reported incidence climbed from 35.5 to a peak of 71.3 cases per million (2000–2008) as China and Vietnam began surveillance, fell to a record low of 2.1 in 2017, then rose to 18.4 in 2019.
• As of September 2019, five countries — Australia, Brunei, Macau, New Zealand and South Korea — were verified as having eliminated rubella.

Rubella cases and first-dose vaccine coverage, WHO Western Pacific Region, 2000–2019. From CDC's MMWR.

Why cases came back

Herd immunity requires about 85% of the population to be immune. Gaps remain because early programs (in 11 countries, 1970–2005) vaccinated only adolescent girls, and because countries that added rubella vaccine for infants didn't vaccinate older people who were already past that age. In 2018, eight countries didn't reach 85% even among their newest birth cohorts.

The 2018–2019 resurgence came from:

Together they caused 98% of the region's cases in those years and involved virus imported from more than 15 countries. China has reported 88% of all regional cases since 2004. Only Japan, the Solomon Islands and Vietnam identified CRS cases after outbreaks.

Surveillance

• Countries reporting rubella data rose from 22 in 2000 to 29 in 2019.
• Only five countries (11% of the region's population) have nationwide CRS surveillance and seven (7%) sentinel surveillance; four countries with 82% of the population, and the 21 Pacific island countries and territories, have none.
• From 2010 to 2018, well-investigated suspected cases rose from 76% to 84%, adequate blood samples from 71% to 82%, and fast lab results from 48% within 7 days to 76% within 4 days.
• Genotypes 1E and 2B circulate widely; 1J, found in four countries before 2013, hasn't been seen since.

Closing the gaps

• Japan is testing adult men for immunity and vaccinating those who are susceptible.
• Vietnam vaccinates children each year in a share of high-risk districts.
• Others have boosted rubella immunity through measles-response campaigns using combined vaccines.
• Funding is a hurdle: only 10 countries are classed as lower-middle income and eligible for some outside support, which isn't well aligned with elimination; the rest must pay their own way, often relying on domestic vaccine makers whose prices and capacity may not fit outbreak needs.

Rubella elimination in the region will require every country to sustain high immunity, close gaps among adolescents and adults, and keep surveillance strong enough to contain outbreaks fast.

Limits: rubella's mildness means many cases go undetected; country comparisons are imperfect; and huge differences in population size mean regional trends can hide small countries' challenges.

Sources

Based on Knapp JK, Mariano KM, Pastore R, et al., "Progress Toward Rubella Elimination — Western Pacific Region, 2000–2019," Morbidity and Mortality Weekly Report 69(24), CDC; a work of the United States government in the public domain.