What historical diseases have resurged from low vaccination rates?
Executive summary
Measles has been the clearest example of a once-controlled disease coming back as vaccination coverage fell: WHO and national reports show outbreaks in high-income countries and Canada lost measles-free status after low coverage produced continuous transmission [1] [2] [3]. Modeling and surveillance link falling childhood immunization to rises in measles, pertussis (whooping cough), polio risk, diphtheria and other vaccine-preventable illnesses — with models projecting millions of cases if coverage declines dramatically [4] [5] [6].
1. Measles: the canary in the vaccination coal mine
Measles routinely resurges first when routine vaccination drops because it is extremely contagious and needs about 95% two-dose coverage to stop transmission; WHO and multiple agencies report recent global surges and re-establishment of endemic transmission in places that had eliminated the disease, including Canada losing its measles-free status after sustained outbreaks tied to pockets of low coverage [1] [2] [3]. Reuters and WHO analyses both note that measles outbreaks in 2024–2025 occurred across 59 countries and in high-income settings, underscoring how even small immunity gaps spark large outbreaks [7] [1].
2. Pertussis (whooping cough): waning immunity plus gaps in coverage
State and federal health officials and news reporting document substantial upticks in pertussis cases in 2024–2025, with states such as Texas reporting thousands of cases and national counts rising sharply; experts attribute outbreaks to falling vaccination rates combined with waning vaccine immunity and surveillance delays [8]. Clinical reporting and mainstream outlets flag pertussis as a present resurgence tied both to immunization decline and to the biological reality that acellular pertussis vaccines confer shorter-lived protection [8] [6].
3. Polio and the specter of paralysis if coverage slips
Modeling studies predict that poliomyelitis could re-emerge if childhood vaccine uptake falls substantially: one simulation projected millions of polio cases under a 50% decline scenario, stressing that long-standing population immunity currently helps but is fragile [4]. Journalistic summaries and modeling papers both warn that polio’s return is a realistic risk if immunization programs continue to weaken [5] [6].
4. Diphtheria, rubella, mumps and other vaccine-preventable infections
Public-health commentary and reporting list diphtheria, rubella, mumps, pneumococcal disease, Hib (Haemophilus influenzae type b), hepatitis and rotavirus among diseases likely to increase as vaccine coverage falls; Reuters and CNN explicitly warn that gaps expose these diseases to resurgence in varied settings [7] [6]. Modeling work frames this as a predictable outcome: declining routine vaccination raises the susceptible population and increases outbreak frequency and scale [4] [5].
5. What the models say about scale and timing
A U.S.-focused simulation estimated that a sustained 50% drop in childhood vaccination could produce tens of millions of measles and rubella cases and millions of polio cases over 25 years, plus hundreds of thousands of hospitalizations and over 150,000 deaths — illustrating not just localized outbreaks but long-term population-level consequences if coverage collapses [4]. Authors caution that timing to a return to endemic transmission varies by disease but that measles is most likely to become endemic first even under current trends [5].
6. Drivers: more than personal choice — systems, disruptions and misinformation
Reporting and reviews attribute falling coverage to a mix of causes: COVID-19–era disruptions to routine services, persistent vaccine hesitancy and misinformation, resource disparities and localized refusal or exemption pockets (including religious or conservative community clusters), and policy shifts that have undermined trust or funding for immunization programs [9] [10] [2]. Public-health sources highlight that many outbreaks concentrated where coverage dropped well below thresholds needed for herd protection [1] [11].
7. Competing views, limitations and what is not yet settled
Surveillance and modeling agree on risk but differ in projections and immediacy: models show catastrophic outcomes under extreme sustained drops [4], while contemporary surveillance shows marked but variable increases in certain diseases now (measles, pertussis) rather than universal re-emergence of all vaccine-preventable illnesses [8] [7]. Available sources do not mention specific claims that every listed disease has already returned nationwide in the U.S.; instead they document outbreaks concentrated in pockets and model potential futures if declines continue [4] [5] [8].
8. Takeaway for policy and the public
The evidence in WHO reports, peer-reviewed modeling and mainstream reporting is consistent: measles has already resurged where coverage fell and is often the first to return; pertussis has risen markedly; modeling warns polio, diphtheria and others could follow if childhood vaccination keeps declining. Reversing these trends requires restoring high routine coverage, addressing access and trust issues highlighted by IVAC and national health agencies, and targeting the specific communities where immunity gaps persist [11] [1] [4].