A mother of four young children recently contacted me, expressing concern about measles. She was prompted by a significant measles outbreak in northwest Texas, which has resulted in confirmed infections, two fatalities, and numerous hospitalizations. This outbreak has since spread to nine other states, and travelers passing through Los Angeles Airport have been issued an alert.
Contrary to popular belief, outbreaks of this potentially fatal disease are uncommon. The U.S. declared measles eliminated over 20 years ago, thanks to a highly effective and safe vaccine. However, efforts to discredit the vaccine have contributed to the recent resurgence. We can take individual and collective actions to safeguard vulnerable populations and hopefully eradicate measles from the country once more.
My friend understands and trusts the scientific evidence supporting the safety and effectiveness of vaccines. She adheres to the vaccination schedule recommended by her pediatrician. Measles vaccines are among the most protective available, ensuring her children’s protection when vaccinated. However, the large outbreaks we are witnessing still pose risks, particularly to young children, immunocompromised individuals, and vulnerable adults.
Measles vaccines are highly effective, providing 93% protection after the first dose and 99% after the second. The challenge lies in the timing of these doses. The first dose is typically administered between 12 and 15 months of age, and the second between 4 and 6 years old. Infants receive some passive immunity from their mothers’ antibodies for the first six months, but this is insufficient for complete protection. Consequently, the U.S. Centers for Disease Control and Prevention advises parents of unvaccinated children to avoid traveling to areas experiencing measles outbreaks.
All children under one year old, before receiving their first measles vaccine, are susceptible to infection if exposed to someone with measles. Given measles’s highly contagious nature, outbreaks are likely to lead to more infections among children in this age group, including those whose parents intend to vaccinate them. While the first dose provides significant protection, optimal protection is achieved after the second dose, usually administered when a child starts school. Between these doses, children remain at risk, especially with repeated exposure to measles from unvaccinated individuals.
Beyond young children, two other groups require special consideration: immunocompromised children and elderly or immunocompromised adults. Immunocompromised children, such as those undergoing cancer treatment, cannot receive the measles vaccine because it contains a weakened live virus that could cause the disease in these individuals. Therefore, they rely on high levels of community immunity for protection. When vaccination rates fall below 95%, the virus can circulate, increasing the risk of infection and severe illness in vulnerable children.
Most elderly individuals should have some immunity to measles, either from contracting the disease before 1957 or from vaccination programs that began in the 1960s. While we generally assume lifelong immunity from infection or vaccination, this is not always certain. For example, if an 80-year-old contracted measles at age 5, is she still protected? What about an adult undergoing chemotherapy? While their immunity may be sufficient, further research is needed to understand the risks of measles exposure in these populations. Measles in an unprotected elderly or immunocompromised adult, whether due to inability to vaccinate or waning immunity, is likely to be severe. Elderly individuals in high-outbreak areas may require an additional booster shot. However, we lack sufficient data to make informed recommendations.
Years of vaccine misinformation have resulted in low vaccination rates in many communities across the U.S. A common argument is that parents only endanger their own children by not vaccinating. However, low vaccination rates create risks for others, including infants too young to be vaccinated, immunocompromised children who cannot be vaccinated, and elderly or immunocompromised adults with weakened immune systems.
Therefore, when my friend with a young child inquired about protection, my advice was clear: avoid areas with outbreaks, vaccinate her child as soon as eligible, and encourage others in her community to do the same. While she can eventually protect her own children, this option is unavailable for a child battling leukemia or for those who are immunocompromised or at risk due to waning immunity. We have a responsibility to eradicate measles from the U.S. once again to protect these vulnerable individuals.