A leading US infectious disease expert warns the world may have entered a “post-herd immunity” era for measles as vaccination gaps spark renewed outbreaks. The United States is contending with its worst measles surge in decades, with more than 930 cases reported this year. The warning underscores how gaps in vaccination can erode community protection and fuel transmission even in previously controlled regions.
For Thai readers, this development matters because declining vaccine coverage worldwide raises the risk of measles returning to countries that had long controlled the disease. Measles had been declared eliminated in many regions thanks to sustained vaccination campaigns, but recent disruptions and misinformation have dented uptake. In the United States and parts of Europe, vaccination rates have fallen below the 95 percent threshold needed for herd immunity, raising concerns about localized outbreaks and spillover to other regions, including Southeast Asia.
Herd immunity hinges on high immunization rates. When about 95 percent of a population is vaccinated, transmission chains break, protecting infants and others who cannot be vaccinated. Experts warn that this threshold is not being met in many places. A prominent health professional from a major children’s hospital described the current situation as a “post-herd immunity world,” noting that a single imported case can spark wider spread due to immunity gaps.
Public health data show a global decline in childhood immunization after the pandemic. The World Health Organization reports measles vaccination rates dipping to 83 percent in 2023, the lowest since 2008. In the United States, coverage often falls short of the 95 percent target, and pockets of lower rates align with anti-vaccine misinformation. Similar patterns have appeared in parts of Southeast Asia, where vaccine hesitancy and service disruptions challenge hard-won gains.
Measles is extremely contagious. A single infected person can spread the virus to a large share of nearby unvaccinated people. Symptoms include high fever, rash, cough, and conjunctivitis, with potential complications such as pneumonia and brain inflammation. In recent years, spikes in cases have appeared in the United States, Great Britain, New Zealand, and several countries in Asia and Africa, often linked to areas with strong vaccine skepticism.
Thailand faces a sobering reminder. The country has battled measles through school-based programs and routine immunizations, achieving high coverage in the past. However, surveys indicate complacency in some communities, gaps among migrant populations, and disruptions during the pandemic that could create susceptible clusters. A senior official from the Department of Disease Control cautioned that lapses in routine immunization leave communities vulnerable, especially as international travel rebounds and an imported case could ignite an outbreak if vigilance fades.
Historically, Thailand has relied on rapid responses to outbreaks, including ring vaccination and community outreach. Officials and health experts emphasize empowering village health volunteers and engaging local leaders to rebuild trust and boost uptake. The new post-herd immunity reality means these approaches must be intensified and complemented by clear public information campaigns to counter misinformation.
Experts also stress the need for catch-up vaccination programs and targeted outreach to migrant communities, remote highland populations, and urban pockets with resistance. Global estimates suggest that further falls in vaccination could lead to millions more measles cases and thousands of deaths annually, with the burden falling hardest on low- and middle-income countries. Even high-income nations are not fully protected in a connected world.
To safeguard children and vulnerable groups, health authorities advocate swift action: ensure two doses of the measles–mumps–rubella vaccine for all children; implement catch-up schemes for older unvaccinated individuals; and expand access through flexible clinics and school-based programs. In Thailand, authorities are reviewing strategies to reach migrant workers, rural communities, and urban zones where hesitancy persists.
Vaccination is culturally viewed in Thailand as a civic duty that protects the whole community. Campaigns alongside trusted figures—monks, teachers, and village leaders—have proven effective in improving acceptance. Rebuilding these partnerships, combined with modern digital outreach, can help address trust gaps and practical barriers exposed by the pandemic.
In summary, the shift to a post-herd immunity era calls for renewed vigilance and collective responsibility. Thai parents should verify their children’s immunization status and take advantage of catch-up services if needed. Health workers recommend relying on accurate information from the Ministry of Public Health, the World Health Organization, and reputable hospitals, while avoiding misinformation on social media.
The measles challenge is not a distant problem; it is a global reminder that sustained high vaccination rates protect the entire community. By staying vigilant and proactive, Thailand can maintain its hard-won gains and shield future generations from resurgent outbreaks.