A child in rural upstate New York has died after contracting measles, marking the state’s first known measles-associated death in more than 30 years.
State officials announced on Monday that the unvaccinated child, who lived in Lewis County, died amid a historic outbreak of the highly contagious disease in the state.
Though measles can infect anyone, the vast majority of global measles-related deaths occur in unvaccinated or under-vaccinated children under age 5, according to the World Health Organization (WHO).
Part of the MMR (measles, mumps and rubella) vaccine, the measles shot is typically administered in two doses because some children don’t develop full immunity after the first.
Vaccination remains the best way to prevent measles and provides long-term, possibly lifelong immunity, with WHO estimating that immunization campaigns prevented 59 million deaths globally between 2000 and 2024.
But if the measles vaccines offers such lasting protection, why are we encouraged to get flu and COVID-19 shots every year?
And why are some vaccines one-and-done while others require annual updates and regular boosters?
Some viruses change faster than others
According to Dr. Isaac P. Dapkins, an internal and pediatric specialist and chief medical officer of the Family Health Centers at NYU Langone, the answer boils down to two main factors: how much the particular infection changes over time and how long our immune system maintains protection after vaccination.
The flu is a prime example of an infection in constant flux. As it spreads from person to person, it undergoes small genetic changes through a process called antigenic drift, Dapkins told The Post.
“These changes can alter the proteins on the surface of the virus, making it harder for our immune system to recognize and fight off new strains, even if we’ve been vaccinated or infected in the past,” he explained.
Because influenza mutates so frequently, scientists worldwide continuously track circulating strains. Public health experts then use this data every year to predict which strains will dominate the upcoming flu season, and manufacturers design updated vaccines to target them.
“Even when the match isn’t perfect, vaccination can still provide meaningful protection, particularly against severe illness and hospitalization,” said Dapkins.
Protection also decreases over time, providing another reason for annual flu shots.
Why some vaccines can last a lifetime
One-and-done shots, like the measles vaccine, follow a very different playbook.
“Although the measles virus does undergo genetic changes, the parts of the virus that our immune system recognizes have remained remarkably stable,” Dapkins noted. This stability triggers a particularly strong and long-lasting immune response that continues to recognize and protect against circulating measles viruses.
After completing the recommended two-dose series, most people develop protection that lasts for decades and often for life, making annual updates or routine boosters unnecessary.
Other vaccines can also provide long-lasting protection after a limited number of doses, including yellow fever, HPV vaccines and RSV, the latter of which is recommended during pregnancy to help protect newborns.
Some also require periodic boosters because immunity gradually wanes, even when the pathogen itself does not change significantly. Tetanus and diphtheria vaccines, for example, generally require a booster every 10 years to maintain protection.
“The bottom line is that vaccines don’t all work on the same schedule because infections don’t all behave the same way,” he said.
“Some viruses, like influenza, change rapidly, and vaccine-induced protection can decrease over time. Others, like measles, remain antigenically stable and generate a durable immune response, allowing vaccination to provide protection that can last a lifetime.”
There are some exceptions, however.
People who have not completed their recommended initial one-and-done vaccination series — such as those who received only one of the two recommended MMR doses — may need additional shots.
