Measles in the US: why cases are surging as vaccination rates fall

Health authorities have confirmed that the number of measles cases reported in the US so far in 2026 has already surpassed the record-breaking total for all of 2025, even though five more months of the year remain. Officials describe the milestone as a clear sign that measles has again become a serious public health concern in the country. Case counts are compiled nationally by the Centers for Disease Control and Prevention, which tracks measles as a notifiable disease, meaning individual states are required to report confirmed cases as they are identified.

Measles is considered one of the most contagious diseases known to medicine. Public health experts say a single infected person in an unprotected community can pass the virus to somewhere between ten and eighteen other people, a transmission rate far higher than that of influenza or most strains of Covid-19. By comparison, seasonal flu typically has a transmission rate of around one to two people per case, illustrating just how efficiently measles can move through a population that lacks protection.

Because it spreads so easily, the vaccination threshold needed to stop measles circulating in a community is unusually high. Health authorities say roughly 95% of a population needs to be protected with two doses of the measles-mumps-rubella (MMR) vaccine to sustain herd immunity, a notably higher bar than for many other vaccine-preventable diseases.

According to STAT News, the national vaccination rate has now fallen below that critical threshold. Officials attribute the decline to growing vaccine hesitancy in some communities and falling participation in routine childhood immunisation schedules, without attributing responsibility to any specific political figure or movement. Officials note that the national average also masks wide variation between communities: some areas maintain vaccination rates well above the threshold, while others have fallen well below it, creating pockets where the virus can spread rapidly once introduced.

In pockets where vaccination coverage is low, a single imported case, often linked to a traveller returning from abroad, can quickly seed a local outbreak. Health officials say much of this year's rise in cases can be traced back to clusters of this kind, with transmission often occurring in schools, places of worship or other settings where unvaccinated people gather in close contact, particularly among young children who have not yet completed the two-dose schedule.

Measles typically begins with a high fever, cough, runny nose and conjunctivitis, followed a few days later by the disease's characteristic rash, which starts on the face and spreads down the body. A significant share of cases can develop serious complications such as pneumonia or brain swelling, and the illness can be fatal, particularly in young children. Health authorities say roughly one in five unvaccinated people who contract measles in the US requires hospitalisation, with complications especially common in children under five and adults over twenty.

The US achieved measles "elimination" status in 2000 thanks to widespread vaccination, meaning the virus no longer circulated continuously within the country for more than twelve months at a time. Health officials warn that sustained local transmission over a long enough period could put that status at risk; losing it would not change how the disease is treated, but officials say it would mark a symbolic setback for a country that has long served as a model for measles control.

In areas experiencing outbreaks, local health departments are running contact tracing, opening additional vaccination clinics in affected communities, and urging families to check their children's immunisation records. Some jurisdictions have also opened temporary vaccination sites at schools and community centres, and issued guidance to childcare facilities and schools about excluding unvaccinated children during active outbreaks.

The World Health Organization has also reported rising measles case counts in numerous countries in recent years, suggesting the trend is not unique to the US and reflects broader global fluctuations in vaccination coverage. The organisation has linked part of the global rise to disruptions in routine immunisation programmes during the Covid-19 pandemic, which left a generation of children with gaps in their vaccination records that have not yet been fully closed.

Health authorities recommend that families check their children's MMR vaccination records and complete any missing doses. Experts say two doses of the vaccine provide roughly 97% protection against measles, and the most effective way to halt an outbreak remains raising community vaccination rates back above the threshold needed for herd immunity. Officials add that it is never too late to catch up on missed doses, and that most primary care providers and public health clinics offer the vaccine at low or no cost.