Hawaii says a vaccinated Oahu resident who traveled to Nevada last month has tested positive for the delta variant of COVID-19.

The delta variant was first detected in India and is a more transmissible version of the disease. The variant currently makes up 6% of all cases in the US.

Hawaii Health Director Dr. Libby Char says this is a “very rare breakthrough” case in which a COVID-19 vaccine didn’t prevent infection.

New analysis from researchers in the UK shows the Pfizer vaccine is 96% effective against hospitalization from the delta variant.