While the world fixates on COVID-19 vaccine development updates, an age-old and incredibly potent inoculation against the measles has become increasingly underused.

The result, according to Dr. Patrick Cahill, a Hartford HealthCare infectious disease specialist in Eastern Connecticut, has been a global increase in the number of people contracting measles and dying.

Measles was considered eradicated in the United States as recently as 2000, but the Centers for Disease Control and Prevention noted almost 1,500 cases in 31 states last year. Worldwide, almost 900,000 recorded cases of measles have been reported, the highest number since 1996. Deaths rose almost 50 percent since 2016 to more than 200,000.

“There has been a decline in measles vaccination rates, and about 95 percent of the cases in the recent outbreaks were people who were unvaccinated,” Dr. Cahill said.

The U.S. outbreaks, he said, have been linked to American travelers venturing abroad and carrying the disease back with them, and populations refusing vaccinations based on religious or other beliefs.

The numbers, Dr. Cahill said, are disturbing for several reasons, especially inclusion of what he called “vaccine hesitancy” as a Top 10 cause of global health concern in 2019. With that in mind, he said he cannot understand the reluctance to vaccinate, especially with the measles vaccine nearly 100 percent effective.

“When you take scientific evidence into account, there are basically no legitimate reasons to not receive vaccinations,” he said.

While flu vaccine, in extremely rare cases, can cause Guillain Barre Syndrome – a situation addressed with versions that exclude egg products – most vaccines contain inactivated versions of the disease, eliminating patients’ risk of contracting it.

He pointed to social media and conspiracy theorists as part of the problem.

“There has certainly been a push to undermine what has been considered to be facts, and this has led many to get wrapped up in conspiracy theories and refuse vaccinations or other socially-accepted norms,” Dr. Cahill said.

In the meantime, he said measles should concern people because it is an extremely effective spreader among people and three times more infectious than COVID-19.

“There have been numbers thrown around during this pandemic called ‘R-naught’ or RO, which indicates the infectious potential of a virus,” he said. “The higher the number is worse. COVID-19 has an RO of under 5. Measles has a value near 15, meaning every infected person may transmit the virus to 15 others.”

The COVID-19 pandemic complicated matters, halting vaccination campaigns worldwide and disrupting normal schedules that means close to 100 million children could go without the vaccine. Remedying that is now a focus for the CDC, the World Health Organization, UNICEF, the United Nations Foundation and the American Red Cross.

Any adult or child who might have missed a regular in-person appointment with their primary care physician should reach out to reschedule any vaccinations and check to be sure they are up-to-date with their vaccination schedule, including measles, Dr. Cahill said.