As measles outbreaks spread rapidly through parts of North America, a top US immunologist has issued a grave warning: the world may now be entering a “post-herd-immunity” era — a phase in which the protective barrier once provided by widespread vaccination has been critically weakened.
Dr. Paul Offit, a renowned infectious disease expert and director of the Vaccine Education Center at Children’s Hospital of Philadelphia, stated bluntly: “We’re living in a post-herd-immunity world. I think the measles outbreak proves that.”
Offit pointed to the highly infectious nature of measles as a warning sign.“Measles – because it is the most contagious of the vaccine-preventable diseases, the most contagious human disease, really – it is the first to come back,” he said.
The United States officially eliminated measles in 2000, but that status is at risk. According to the CDC, if the country experiences 12 continuous months of sustained measles transmission, it could lose its elimination designation. As of 1 May, the CDC had recorded 935 confirmed cases across 30 jurisdictions, with 285 children under five hospitalized, nearly one-third of all infected young children.
Outbreaks in Texas, New Mexico, and Oklahoma are currently the epicenter in the US, particularly in Gaines County, Texas, where three deaths have occurred — two unvaccinated children and one adult. These outbreaks, along with surges in Canada and Mexico, now account for the bulk of the 2,300 measles cases reported across the World Health Organization’s Americas region. The WHO warns that measles risk in the Americas has grown 11-fold compared to 2024.
Leticia Ruíz, director of prevention and disease control in Chihuahua, Mexico, told the Associated Press: “This virus was imported, traveling country to country.”
What is 'Post-Herd Immunity'?
As per WHO, herd immunity occurs when a large portion of a population becomes immune to a disease, either through vaccination or prior illness, making person-to-person spread unlikely. For measles, about 95% of the population needs to be vaccinated with two doses of the MMR (measles, mumps, rubella) vaccine to maintain herd immunity.
In this context, the “post-herd-immunity” state refers to the breakdown of this protection, often due to declining vaccination rates , misinformation, and reduced public health outreach — conditions now visible in multiple regions.
Europe is faring no better. 2024 was the worst for measles in Europe and Central Asia since 1997, with more than 120,000 cases reported across the region. So far in 2025, about 4,500 measles cases have been reported across the European Union, as per the European Centre for Disease Prevention and Control (ECDC).
Misinformation and policy threats undermining immunity
Health experts have raised alarms over the role of political leadership in eroding vaccine confidence. US Health Secretary Robert F Kennedy Jr has made repeated misleading claims about vaccines. While he has occasionally endorsed the MMR vaccine, he has also falsely stated that it contains “aborted fetus debris.”
Despite overwhelming scientific consensus that prevention through vaccination is the only effective tool against measles, Kennedy has promoted unproven treatments. During a visit to the most affected area in Texas, he claimed that antibiotics like clarithromycin and steroids like budesonide led to “miraculous and instantaneous recovery” — despite the fact that measles is a viral illness, and no cure exists.
The American Academy of Pediatrics responded firmly: “There is no cure for measles, and it can result in serious complications. It’s misleading and dangerous to promote the idea that measles is easily treated using unproven and ineffective therapies like budesonide and clarithromycin.”
Measles can cause encephalitis (brain swelling), long-term disability, and death. It suppresses the immune system, leaving individuals vulnerable to other infections. Globally, measles vaccination has saved more than 60 million lives between 2000 and 2023, according to public health estimates.
Dr. Paul Offit, a renowned infectious disease expert and director of the Vaccine Education Center at Children’s Hospital of Philadelphia, stated bluntly: “We’re living in a post-herd-immunity world. I think the measles outbreak proves that.”
Offit pointed to the highly infectious nature of measles as a warning sign.“Measles – because it is the most contagious of the vaccine-preventable diseases, the most contagious human disease, really – it is the first to come back,” he said.
The United States officially eliminated measles in 2000, but that status is at risk. According to the CDC, if the country experiences 12 continuous months of sustained measles transmission, it could lose its elimination designation. As of 1 May, the CDC had recorded 935 confirmed cases across 30 jurisdictions, with 285 children under five hospitalized, nearly one-third of all infected young children. Outbreaks in Texas, New Mexico, and Oklahoma are currently the epicenter in the US, particularly in Gaines County, Texas, where three deaths have occurred — two unvaccinated children and one adult. These outbreaks, along with surges in Canada and Mexico, now account for the bulk of the 2,300 measles cases reported across the World Health Organization’s Americas region. The WHO warns that measles risk in the Americas has grown 11-fold compared to 2024.
Leticia Ruíz, director of prevention and disease control in Chihuahua, Mexico, told the Associated Press: “This virus was imported, traveling country to country.”
What is 'Post-Herd Immunity'?
As per WHO, herd immunity occurs when a large portion of a population becomes immune to a disease, either through vaccination or prior illness, making person-to-person spread unlikely. For measles, about 95% of the population needs to be vaccinated with two doses of the MMR (measles, mumps, rubella) vaccine to maintain herd immunity.
In this context, the “post-herd-immunity” state refers to the breakdown of this protection, often due to declining vaccination rates , misinformation, and reduced public health outreach — conditions now visible in multiple regions.
Europe is faring no better. 2024 was the worst for measles in Europe and Central Asia since 1997, with more than 120,000 cases reported across the region. So far in 2025, about 4,500 measles cases have been reported across the European Union, as per the European Centre for Disease Prevention and Control (ECDC).
Misinformation and policy threats undermining immunity
Health experts have raised alarms over the role of political leadership in eroding vaccine confidence. US Health Secretary Robert F Kennedy Jr has made repeated misleading claims about vaccines. While he has occasionally endorsed the MMR vaccine, he has also falsely stated that it contains “aborted fetus debris.”
Despite overwhelming scientific consensus that prevention through vaccination is the only effective tool against measles, Kennedy has promoted unproven treatments. During a visit to the most affected area in Texas, he claimed that antibiotics like clarithromycin and steroids like budesonide led to “miraculous and instantaneous recovery” — despite the fact that measles is a viral illness, and no cure exists.
The American Academy of Pediatrics responded firmly: “There is no cure for measles, and it can result in serious complications. It’s misleading and dangerous to promote the idea that measles is easily treated using unproven and ineffective therapies like budesonide and clarithromycin.”
Measles can cause encephalitis (brain swelling), long-term disability, and death. It suppresses the immune system, leaving individuals vulnerable to other infections. Globally, measles vaccination has saved more than 60 million lives between 2000 and 2023, according to public health estimates.
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