By Col. (Ret.) Zygmunt Dembek
Col. (Ret.) Zygmunt Dembek discusses the recent increase in global measles cases and explains how the rise is related to COVID-19.
Measles – also known as rubeola – is the most highly transmissible respiratory disease that is also vaccine preventable. Measles has a person-to-person transmission rate (R0) of 12-18, indicating that each person infected by measles can then infect 12-18 additional individuals. Anyone who is not protected by immunization, whether by vaccination or naturally acquired illness, is at risk of contracting measles.
Measles has a 10–15-day incubation period. Following this period, a maculopapular rash develops. This is a rash that has both macules and papules, i.e. flat and raised red bumps on the skin. The rash often originates from the facial region and then spreads over the body to the extremities. Common measles symptoms also include a high fever, cough, runny nose, and watery eyes. Patients are contagious and can infect others from four days before symptom onset until four days after the rash disappears.
While most individuals infected with measles usually recover from infection without significant adverse events, complications can occur more frequently in children under five years old, in pregnant women, and in immunocompromised individuals. Pneumonia, whether caused directly from the measles infection or as a secondary infection, is a frequent complication. Encephalitis occurs in about 1 in 1,000 cases, mostly affecting immunocompromised individuals. Globally, and particularly in areas where public health measures are lacking, there are more than 100,000 deaths annually from measles.
A suspected case of measles can be determined by a medical diagnosis based on symptoms of fever, rash, and medical history of the patient. Confirmation of measles is by laboratory diagnosis with detection of IgM antibody in serum samples and measles virus RNA via a reverse transcription polymerase chain reaction (RT-PCR) in a respiratory specimen.
Measles Vaccine and Vaccination Goals
Measles vaccines are highly effective. There are various formulations of measles vaccines available, including monovalent, bivalent (against measles and rubella, MR), trivalent (against measles, mumps, and rubella, MMR), and quadrivalent (against measles, mumps, rubella, and varicella, MMRV). A vaccine efficacy of 97% measles prevention is achieved following two vaccine doses, while a single dose is 93% effective. Generally, those receiving the MMR vaccine have lifetime protection from contracting measles.
The World Health Organization (WHO) goal is to have at least 95% population vaccine coverage with two measles vaccine doses to assure ‘herd immunity’, or a protective immunity within a population, and to prevent outbreaks among the remaining unvaccinated population. This is important since public health scientists have learned that measles is especially sensitive to changes in herd immunity and can readily spread in areas that are under-vaccinated.
Measles Outbreaks in Europe and Central Asia
In 2023, measles cases in Europe and Central Asia surged by 3000% on the previous year. Intensive measles reduction efforts have been ongoing by the governments and public health agencies in these nations, with assistance from the WHO, United Nations Children’s Fund – UNICEF, and Gavi, the Vaccine Alliance. Countries worldwide having the greatest number of measles cases globally during 2023 include, in descending order of those with the largest case numbers: Yemen, India, Kazakhstan, Ethiopia, Pakistan, Democratic Republic of the Congo, Russia, Iraq, Indonesia, and Nigeria.
In 2023, there were over 42,000 measles cases in 41 of 53 WHO European region countries with thousands of hospitalizations and 10 measles-related deaths. This represents a rapid spread of measles in this region when compared to previous years. Almost half of these cases were among children under five years of age, revealing missed childhood vaccinations. In the U.K., the total number of laboratory-confirmed measles cases since October 1, 2023, continues to increase and is now over 700 cases at the time of writing.
The WHO estimates that there are approximately 1.2 million children within this European region who have missed their measles vaccination between 2020 and 2022. The WHO Regional Director for Europe, Dr. Hans Kluge, has stated that: “Health systems in the WHO European Region have some catching up to do to rapidly reach the 1.2 million children who missed their measles vaccine between 2020 and 2022 while continuing with routine immunization.”
He further said: “As the virus continues to spread in many parts of the Region, timely outbreak detection and response remains critical to prevent further escalation and secure the Region’s progress towards eliminating this highly contagious disease.”
Measles in the United States
Measles was declared eliminated in the U.S. in 2000. The WHO defines measles elimination as “the absence of endemic measles virus transmission in a defined geographical area (e.g. region or country) for at least 12 months in the presence of a surveillance system that has been verified to be performing well”.
In 2019 the U.S. was at risk of losing its recognized measles elimination status because of several large outbreaks, with over 1200 confirmed cases in 31 states. At that time, there had been about 10 years of increasing measles incidence in the U.S. Among the most significant outbreaks were in Disneyland (California) in 2014-2015 that spread to 11 states and to Canada and Mexico, and in 2018-2019, primarily among Orthodox Jewish communities in New York City and Rockland County.
The Covid Pandemic Effect
The present surge in measles cases is due to the COVID-19 pandemic’s effect on routine childhood vaccination programs, with resulting missed vaccinations. A direct result of the pandemic is that there is now a significant population of children susceptible to measles. These children have not only missed their measles vaccination, but also other childhood vaccine-preventable disease vaccinations. Other vaccine-preventable diseases normally received in childhood that were also missed during the COVID-19 pandemic include: chickenpox, diphtheria, influenza, hepatitis A and B, Haemophilus influenza type B, human papillomavirus, meningococcal disease, mumps, polio, pneumococcal disease, rotavirus, respiratory syncytial virus, rubella, tetanus, and whooping cough. These other diseases could also enjoy a reappearance among children and adults. The harbinger of such outbreaks is measles, given its very high transmissibility that leads to rapid disease spread. It is hoped that children now receiving delayed measles vaccinations will also receive other missed vaccines normally received in childhood for vaccine-preventable diseases.
Ongoing National Measles Immunization and Prevention Campaigns
A sustained vaccination campaign is needed to prevent measles cases from continuing to rise in Europe in 2024. Given that there is a global rise in measles cases, the risk of importing measles into Europe is unavoidable. European nations have strengthened disease surveillance for early measles case detection with rapid epidemiologic case contact. They have considerably increased normal childhood immunization efforts and conducted immunization activities to vaccinate vulnerable individuals before measles infection.
Mass measles vaccination campaigns were undertaken during 2023 in Armenia, Kazakhstan, Kyrgyzstan, Romania, and Tajikistan, resulting in over 2.5 million children of all ages vaccinated in 2023. This appears to have helped curb the spread of the virus in these countries. However, transmission continues in the region, posing an ongoing threat to millions of children.
Kazakhstan had the highest recorded measles incidence of the WHO European Region, with 13,677 cases during 2023. Of these cases, 83% were under 14 years of age, and 65% were under five years of age. As of January 23, 2024, there were 2,167 children hospitalized in Kazakhstan with measles, with 27 in a serious condition. Kazakhstan’s extensive public health response to this epidemic includes:
- Isolating patients with confirmed disease;
- Daily medical observation provided for all contacts for 21 days;
- All contacts under 30 years old are vaccinated;
- Supplementary immunization activities include offering an early dose of MMR vaccine to children aged 6–10 months, a potentially supplemental dose to all children aged 2–4 years regardless of previous vaccination status, and vaccination to unvaccinated health workers;
- Catch-up immunization for all children <18 years of age who missed routine vaccination;
- A public education campaign with particular focus on measles.
A national immunization catch-up campaign was initiated in Armenia. Supplementary MMR and measles vaccine immunization campaigns have been implemented in Kyrgyzstan and Tajikistan.
European Immunization Agenda 2030
All countries in the WHO European Region have adopted the European Immunization Agenda 2030 that requires them to:
- Achieve and sustain over 95% coverage in all communities with two doses of measles-containing vaccine, including offering catch-up vaccination to those who missed either vaccine dose;
- Ensure high-quality surveillance to quickly detect and isolate any possible cases;
- Ensure rapid outbreak response in all communities.
Along with ensuring measles immunity through vaccination, practicing good hand hygiene and cough etiquette are important tools that can reduce the virus spread. Anyone experiencing measles symptoms should seek prompt medical attention to prevent further disease transmission.
Summary
The current outbreaks of measles in the WHO European Region, in the U.S., and throughout the world are a part of the legacy of the COVID-19 pandemic, where massive numbers of childhood immunizations were missed. Given the ramping up of immunization and public health awareness programs, it is hoped that the current global surge in measles cases can be quickly controlled. It is important that any other missed childhood vaccinations also be provided to this at-risk population of children, to be able to create and sustain herd immunity and contain future outbreaks of these diseases.
Col. (Ret.) Zygmunt F. Dembek is an epidemiologist and biochemist. He has written extensively on biodefense and has conducted pandemic preparedness exercises worldwide.
