The Impact of Slight Declines in Vaccination Rates on Measles Endemic Risk

How Marginal Drops in Vaccination Coverage Threaten to Reignite Measles

It takes only a small decline in vaccination rates to significantly increase the risk of measles becoming endemic once again. Recent research warns that even slight decreases in childhood immunization coverage can lead to a resurgence of this highly contagious disease, which was close to being eradicated in many regions.

A new study published in JAMA utilized sophisticated modeling to assess how falling vaccination rates for measles, rubella, polio, and diphtheria could impact public health. The findings reveal that, at current vaccination levels, measles could infect over 850,000 individuals annually in the United States alone, resulting in more than 2,500 deaths each year. Alarmingly, just a 10% reduction in vaccination coverage could cause cases to escalate to over 11 million annually.

Measles is among the most contagious infectious diseases known to science, with a single person infectious enough to spread the virus to between 12 and 18 others. This transmission rate exceeds that of illnesses like influenza and COVID-19 by a significant margin. To prevent such rapid spread, health authorities recommend that at least 95% of the population be vaccinated. However, vaccination rates are falling short globally, including in countries like England, where less than 84% of five-year-olds received both doses of the MMR vaccine in 2024.

This decline in immunization presents a serious health threat because measles can lead to severe complications. About 20% of children with measles require hospitalization; pneumonia develops in 5%, and encephelitis—a brain infection—can cause long-term damage or death in 0.1% of cases. Moreover, measles can weaken the immune system, making children vulnerable to other infections.

If vaccination coverage continues to decline, other vaccine-preventable diseases could also regain prevalence. Rubella, for example, can cause devastating birth defects; polio may lead to permanent paralysis; and diphtheria remains deadly in unvaccinated populations.

Historically, in regions where vaccine coverage has been below the 95% threshold, these diseases have become endemic—circulating continually rather than causing isolated outbreaks. Unfortunately, vaccine hesitancy fueled by misinformation, concerns over vaccine safety, and complacency are major barriers to achieving high immunization coverage. Myths, such as unfounded links between the MMR vaccine and autism, have been thoroughly debunked but continue to influence public opinion.

The persistence of false information coupled with decreased vaccination can cause outbreaks, as seen in the United States with nearly 900 reported measles cases in 2025, including three fatalities. This situation underscores the importance of herd immunity; when more than 95% of a community is vaccinated, the virus cannot spread effectively, protecting even those who cannot be vaccinated due to age, allergies, or health conditions.

Contributing factors to declining vaccination rates include the aftermath of the COVID-19 pandemic, natural disasters, conflicts, and ongoing logistical challenges. Addressing vaccine hesitancy requires public education, transparent communication about vaccine safety, and strategies to combat misinformation.

Vaccines remain one of the most effective tools for disease prevention. The MMR vaccine, in particular, offers over 97% protection when both doses are administered. Maintaining high vaccination coverage is essential for preventing the resurgence of measles and other preventable diseases, safeguarding the health of future generations.

Source: medicalxpress.com