In less than two months, the number of suspected measles cases in North Sumatra nearly doubled — from 387 cases recorded on March 5, 2026 to 748 cases as of April 30, 2026, according to data from the North Sumatra Provincial Health Agency released by The Jakarta Post. This figure is more than just a local health crisis. It is a symptom of a syndrome that the global health community has long warned about: when vaccination rates collapse below herd immunity thresholds, even diseases with proven effective vaccines from decades past return and strike again.
The gap between what is required and reality in Medan is a chasm, not a distance.
How low are vaccination rates?
Numbers from the North Sumatra Provincial Health Agency would give any public health expert pause. According to Hamid Rijal, secretary of the Provincial Health Agency, the full vaccination rate for infants in Medan — the province's largest city — reached only 7.6% in April 2026. In Simalungun district it was 22.77%, and in Deli Serdang 31.48%.
To understand just how serious these figures are, they must be placed in the context of international medical science. According to the World Health Organization (WHO), the herd immunity threshold for measles — one of the most contagious viral diseases with an estimated R0 transmission rate of 12 to 18 people per infection — requires a minimum vaccination rate of 92 to 95% of the population. The gap between what is required and reality in Medan (7.6%) is a chasm, not a distance.
The three districts with the highest disease density — Medan, Deli Serdang and Simalungun — have been declared "kejadian luar biasa" (KLB), or unusual disease outbreak status, using Indonesian public health terminology. However, according to Hamid, provincial authorities have yet to escalate to declaring KLB at the provincial level — an administrative decision that is symbolic but important because it triggers additional higher-level response resources.
Empty vaccine stores and the crisis loop
The most alarming development in this story is not the increase in cases — that was predictable given such low vaccination rates. What is more concerning is that the provincial stockpile of Measles-Rubella (MR) vaccine has been completely depleted right in the middle of the outbreak.
Hamid confirmed this is not the first time: earlier in 2026, the province experienced a shortage of MR vaccine for about two months. This creates a dangerous loop: vaccine shortage → falling vaccination rates → herd immunity collapse → disease outbreak → system lacks sufficient vaccine to respond. According to Hamid, provincial budget is insufficient to expand vaccination coverage, and vaccine supply issues are a structural bottleneck, not a temporary problem.
This raises important questions about Indonesia's national vaccine supply chain. MR vaccine is produced by Bio Farma — Indonesia's state pharmaceutical company — and is also imported through Gavi (Global Alliance for Vaccines and Immunization) mechanisms and international health aid programs. However, according to public health experts cited by The Jakarta Post, the problem is not just supply shortage but also uneven distribution among provinces and delays in public procurement procedures.
Eroded trust: The role of misinformation in disease outbreak
If vaccine shortage is a supply-side problem, vaccine refusal is a demand-side problem — and both are now amplifying each other to create disaster.
Hamid Rijal confirmed that "many people refuse vaccination because of rumors that vaccines harm the body." This is not unique to North Sumatra. Dr. Destanul Aulia, chairman of the North Sumatra branch of the Indonesian Association of Public Health Experts (IAKMI), stated to The Jakarta Post on May 15, 2026 that "this phenomenon is also occurring in many other countries, not just Indonesia.
He is right. The anti-vaccine movement — amplified through social media — has directly contributed to measles outbreaks in the United States, Europe and many other places over the past decade. According to the U.S. CDC (Centers for Disease Control and Prevention), in 2019 the United States recorded over 1,200 measles cases — the highest level since 1992 — largely originating from communities with low vaccination rates due to misinformation. Indonesia is repeating that scenario with significantly different scale and healthcare infrastructure conditions — and therefore consequences could be more severe.
The high mobility of North Sumatra residents — a point both Hamid and Dr. Destanul emphasized — accelerates cross-regional transmission. North Sumatra is Indonesia's third most populous province with over 15 million people, according to Indonesia's Central Statistics Agency (BPS). Trade corridors and internal migration routes — particularly between Medan and neighboring districts — create conditions for measles virus to spread rapidly through unprotected communities.
System gaps: Delayed detection and late response
Beyond vaccine shortages and vaccination refusal, Dr. Destanul points to a third factor: slow disease detection capability and epidemiological response. He stated that according to Indonesia's guidelines for managing measles KLB outbreaks, outbreak response immunization campaigns (ORI) must be deployed within seven days of detecting outbreak signs.
Reality in North Sumatra shows a considerable gap between theory and practice: suspected cases nearly doubled in less than two months, but by mid-May 2026 the province had still not declared provincial-level KLB and ORI vaccine stockpiles had not been adequately replenished. According to Hamid, current plans call for ORI and PENARI catch-up vaccination programs within a one-week framework — but vaccine shortage is a direct barrier even to this minimal plan.
Dr. Destanul also noted that in 2025, the province faced difficulties expanding booster vaccination campaigns due to three concurrent problems: limited geographic accessibility, lack of health education and communication, and vaccine skepticism. These three issues cannot be solved by a short-term vaccination campaign.
The perspective of overseas Vietnamese communities: A lesson that cannot be missed
For Vietnamese communities in the United States — particularly in densely populated centers like Little Saigon in Orange County, California and Houston, Texas — the North Sumatra story is not about distant foreign events. It is a mirror reflecting real risks in immigrant communities.
First, the problem of vaccine misinformation within Vietnamese-American communities is also a concerning reality. During the COVID-19 pandemic, research conducted by organizations like UCSF (University of California at San Francisco) and Stanford documented higher-than-average vaccine hesitancy rates in some Asian-origin communities, including Vietnamese, partly due to misinformation spreading through Vietnamese-language social media.
Second, many Vietnamese-American families maintain direct connections to Southeast Asia — not only to Vietnam but also to ethnic Chinese Vietnamese, Cham, and other communities in Indonesia, Malaysia and neighboring countries. Travel, visiting relatives and commerce are routes through which disease — including measles — can travel if vaccination rates in the source region are low.
Third, the North Sumatra story illustrates concretely what public health experts in the United States like Dr. Paul Offit (Philadelphia Children's Hospital) and many colleagues have warned about for years: herd immunity is a global public good. When any geographic area — whether in Indonesia or in a community in the United States — has low vaccination rates, it creates weakness for everyone, regardless of national borders.
Regional comparison: Vietnam and lessons from Jakarta
Within Southeast Asia, North Sumatra is not an exception — but the scale and speed of escalation of this outbreak warrants attention from regional health systems, including Vietnam.
Vietnam has experienced serious measles outbreaks in the past, notably in 2014 when hundreds of children died. Subsequently, Vietnam's Ministry of Health intensified its expanded immunization program. According to reports from WHO and UNICEF, MR vaccine coverage rates in Vietnam in recent years have achieved relatively higher levels compared to some neighboring countries — but uneven distribution between regions, particularly in remote and mountainous areas, remains a latent risk.
The failure model in North Sumatra — insufficient local budgets, broken vaccine supply chains, vaccine misinformation spreading widely, and slow epidemiological response capacity — is a model that could emerge in any decentralized health system lacking sufficient central monitoring and reserve mechanisms.
Outlook and what to watch
In the short term, North Sumatra is in a race against time. Provincial health authorities say they will implement ORI and PENARI — but without vaccines there can be no vaccination campaigns. The most immediate question is: when and from where will supplemental vaccine supplies arrive, and will Indonesia's central government intervene quickly enough to prevent provincial-level KLB escalation?
In the medium term, the North Sumatra case will be an important test for Indonesia's decentralized health system — a model many Southeast Asian countries pursue. Health decentralization offers flexibility, but also creates "pockets of population" left outside the reach of health services, as Dr. Destanul accurately described.
In the long term, the North Sumatra story reminds us of something public health professionals have long known but policymakers often forget in peacetime: vaccines do not inject themselves into people. Between the vaccine vials in storage and actual injection needles lies an entire ecosystem comprising logistics, health communication, community trust, and budget. When any link in that chain breaks, disease does not need an invitation — it comes on its own.