Hawaiʻi vaccination rates fall short for herd immunity to measles

Parts of the United States are experiencing a measles outbreak, and Hawaiʻi is not immune to the threat.

With the state’s measles vaccination rate at 90%, according to the Hawaiʻi Department of Health, it falls short of the 95% needed for herd immunity, raising concerns about the vulnerability of children and immunocompromised people if—or when—an outbreak makes its way to the islands.

Intensive care physician Dr. Philip Verhoef, who is also an associate clinical professor at the John A. Burns School of Medicine at the University of Hawaiʻi at Mānoa, recently discussed the ongoing measles outbreak and the critical role of vaccinations in protecting public health.

In an interview with a local news outlet, Verhoef expressed deep concern for the low measles immunization rate, especially on neighbor islands.

“There are many children who haven’t received the vaccines they need, which puts them and others at risk. We need to do everything we can to ensure our children are protected,” Verhoef said. “Measles is incredibly contagious—if 10 unimmunized people are exposed, nine will likely develop the disease. The virus can remain in a room for up to two hours after an infected person leaves.”

According to Verhoef, the measles virus can remain in a room for up to two hours after an infected person leaves, making it even easier to contract without direct contact.

“Measles is incredibly contagious—if 10 unimmunized people are exposed, nine will likely develop the disease,” Verhoef said. “Measles starts with high fever, cough, runny nose, and red and watery eyes, followed by a rash at the hairline on day 14. It can lead to complications like pneumonia, brain swelling, and increased infection risk.”

The disease is especially detrimental to children, with approximately one in five children who are infected with measles requiring hospitalization. From there, many will develop pneumonia and require additional breathing support, such as the use of oxygen and mechanical ventilators.

In addition, infection with measles can lead to seizure disorders, brain inflammation (encephalitis), difficulty with hearing and vision, and death in approximately 0.1% to 0.3% of children.

In 1974, measles was among the first diseases targeted by the World Health Organization Expanded Program on Immunization (now the Essential Program on Immunization) to develop and expand immunization programs worldwide.

According to the World Health Organization, widespread childhood vaccination against measles has drastically reduced disease rates worldwide and it is now a recommended vaccination with the first dose given at 1 year of age and a second dose administered around age 4 or 5.

The measles, mumps, and rubella (MMR) vaccine is highly effective—93% effective with one dose and 97% with two. However, to limit the spread of measles, about 95% of the population needs to be immunized, Verhoef said.

“The vaccine is very safe. A mild fever is a common side effect, but this is simply the immune system reacting to the vaccine,” Verhoef said. “The risks of the vaccine are far outweighed by the benefits of preventing a potentially deadly disease.”

For more information on measles and vaccination, visit the Hawaiʻi Department of Health website.