Hawaiian health officials said Monday that a fully vaccinated resident who traveled to Nevada last month has since tested positive for the Delta coronavirus variant. The resident, who lives in Oahu, tested negative for COVID-19 before departing Nevada but developed mild symptoms several days after returning home.
The resident, whose age and sex were not disclosed, isolated after testing positive and close contacts began quarantining. No secondary transmission has been reported.
The state's health director called it a "very rare breakthrough" case.
"The vaccines not only help protect against infection, they protect against severe illness," Dr. Elizabeth Char, said in the news release. "While this is one of those very rare breakthrough cases in which the vaccine did not prevent infection, the infected person did not suffer severe illness."
It was not clear which COVID-19 vaccine the Oahu resident had received prior to infection, but a recent study in the U.K. suggests that the Pfizer jab is 96% effective against hospitalization from the Delta variant.
The Delta variant, which is now listed as a variant of concern by the Centers for Disease Control and Prevention (CDC), accounts for about 6% of all coronavirus cases in the U.S. Officials have warned that it is likely to become the dominant strain given the rate of spread.
"Early evidence suggests the Delta variant might spread more quickly than other SARS-CoV-2 strains," Edward Desmond, Hawaii's state laboratories division administrator, said in the news release. "There are reports the Delta variant produces a higher rate of severe illness than original COVID-19, but we do not yet have enough evidence to support that conclusion."
Char pleaded that "everyone who is eligible" gets vaccinated to stop the spread of COVID-19 and emerging variants.
The Associated Press contributed to this report.