Recent outbreaks of measles, diphtheria and polio across the US and Europe highlight the consequences of declining vaccination rates and eroding herd immunity, raising concerns over the resurgence of preventable diseases.
Measles deaths in Pennsylvania have renewed concern about a disease the United States once said it had eliminated, but the broader picture is less about the virus changing than about protection fraying. The World Health Organization said the recent US outbreak involved hundreds of cases across multiple states, mostly among unvaccinated children, while the rise in infections points to the same problem seen in other countries: when vaccination rates slip, old pathogens regain room to spread. According to WHO, the first US measles death in a decade was recorded in Texas in February 2025, and the agency later said the outbreak stretched across 17 states.
Europe has seen the same pattern on a far larger scale. WHO and UNICEF reported 127,350 measles cases in the European region in 2024, the highest total since 1997 and roughly double the previous year, with children under five making up a large share of cases and many needing hospital care. Although the tally fell in 2025, health agencies warned that the risk of further outbreaks remained because vaccination gaps persist in particular communities. The concern is not confined to measles: Italy recently recorded a fatal diphtheria case in an unvaccinated four-year-old girl, and the European Union has continued to report diphtheria infections linked to both toxigenic Corynebacterium diphtheriae and Corynebacterium ulcerans.
Polio has also reappeared in places where it had long been absent from everyday clinical life. The United States reported paralytic polio in an unvaccinated adult in New York in 2022, the first domestic case since 2013, and genetically related virus was later found in wastewater, suggesting community transmission. Germany has since reported wild poliovirus type 1 in a Hamburg wastewater sample, while Finland, Germany, Poland and Spain detected vaccine-derived polioviruses in wastewater in 2024, prompting the European Centre for Disease Prevention and Control to call for stronger vaccination and surveillance. The message from public health officials is clear: vaccines are still working, but herd protection weakens once coverage falls far enough.
That erosion has been building for years. A recent analysis in The Lancet found that routine childhood vaccination has prevented an estimated 154 million deaths since 1974, yet progress has slowed since 2010 and at least one recommended vaccine declined in 21 of 36 high-income countries studied. The same work found that first-dose measles vaccination fell between 2010 and 2023 in 100 of 204 countries, including France, Italy, Japan, the UK and the US. Researchers pointed to stagnating immunisation programmes, pandemic disruption, inequality and vaccine hesitancy as overlapping causes. WHO and UNICEF have warned that the challenge is no longer simply to restore lost ground after Covid-19, but to close stubborn immunity gaps before more preventable diseases regain a foothold.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
