Vaccinations in 2026

Ashley Sands, MD; and Keith Hansen, MD
January 2, 2026

Vaccination is one of medicine’s most important discoveries and has reduced morbidity and mortality for untold numbers of people, especially vulnerable individuals including the newborn, fetus, elderly and the immunocompromised. One example of the success of vaccinations has been the eradication of smallpox (due to variola virus) in 1980 due to a global universal immunization campaign. Smallpox was a very deadly and disfiguring infectious disease, killing millions of people worldwide. Prior to the development of the smallpox vaccine, it was noted that people who survived an infection were more resistant or immune to a second infection. The first efforts in immunization, or in this case, variolation, were from people scratching material from a smallpox pustule into the skin of a previously uninfected individual, leading to a “mild” case of smallpox in the hope of inducing immunity to the dreaded disease. However, the virus did not always behave itself, resulting in a number of people dying from contracting the disease after exposure. Edward Jenner published his seminal work in 1758 on the use of cowpox immunization conferring immunity to smallpox. This publication launched the era of discovery of successful disease prevention through immunization.  

Another example of a successful vaccination was the development of the rubella or German measles vaccine. German measles, while often a mild illness to a healthy adult or child, can be devastating to the developing fetus if a pregnant woman is infected. Congenital rubella infections can lead to miscarriage, stillbirth, and a constellation of birth defects including blindness, deafness, impaired growth, heart defects, inflammation and intellectual disability (congenital rubella syndrome). Prior to the introduction of the rubella vaccine in 1960s, there were large rubella epidemics in Europe and the U.S. From 1962 to 1965, there were an estimated 12.5 million infections resulting in over 11,000 miscarriages and stillbirths, 2,100 neonatal deaths, and 20,000 babies affected by congenital rubella syndrome in the U.S. The development of the rubella vaccine resulted in a significant drop in cases in the U.S., almost eliminating the disease. The CDC notes that since 2012 the only documented cases of rubella in the U.S. have resulted from infection when people have lived or traveled to areas of the world where the infection is still endemic. There are still many countries and regions of the world where rubella vaccination has not been sufficient to reach herd immunity.

Herd immunity results when a substantial number of individuals are immune to an infection either through having previously had the illness or through vaccination. Herd immunity decreases or halts the spread of an illness by making it difficult for an organism such as a virus to find a susceptible host. When members of a community are noted to be immune, the more vulnerable members of our community, including pregnant women and their babies, young infants, the elderly, and those who are immunocompromised, are thought to be protected from a particular infection. The number of immune individuals required to result in herd immunity is highly dependent on the contagiousness of the disease; a highly contagious disease like measles requires that over 93-95% of individuals are immune for herd immunity. Besides the need for a high number of individuals to be immune, herd immunity also needs homogenous interaction between people within the population. For example, many of our communities in South Dakota show more than 90% of schoolchildren have been vaccinated against measles, but within one school in a community, less than 50% of the children have been immunized. In this case, an individual infected with measles who goes to that school could very easily cause an outbreak in the school and their larger community. Other factors that impact herd immunity include mutations within the organism that were not covered by the vaccine, which we see with highly mutable influenza and COVID-19 viruses. Additionally, because immunity from vaccinations can wane over time, it is important for individuals to update their vaccinations according to the prescribed schedules.

In South Dakota, there has been a reduction in the number of individuals receiving vaccinations, including those needed to start school, many claiming religious exemptions. As a result, the number of individuals receiving the measles vaccine has consistently dropped below the level required for herd immunity. Some counties report vaccination rates well under 80% and multiple schools report that no kindergarteners have been vaccinated against measles. This opens the door for measles to get a foothold in the state, with its increased morbidity and mortality. Because rubella is part of the MMR vaccine, continued decreases in MMR vaccination rates increase the risk of another outbreak of rubella in the U.S., which could lead to significant morbidity and mortality for a developing fetus. In a recent survey, most people noted that they rely on their physician to supply information about vaccinations. It is important that we continue to discuss the importance, efficacy, and safety of vaccinations with our patients not only to protect their health, but for the health of the most vulnerable among us.

In the last issue of South Dakota Medicine, Bruce Vogt, MD introduced our new Historical Series. In this issue, he wrote an article for the Historical Series titled “A Brief History of the Discovery of Vaccines and Vaccinations” which goes into more depth about this very important medical innovation. Over the coming months, the Historical Series will explore topics on the history of medicine, the medical innovations and some historical figures from South Dakota. I hope you enjoy this series of articles.