A fully vaccinated Oahu health care worker contracted COVID-19 after a recent trip to the mainland but has no symptoms.

The Department of Health said Thursday in its weekly cluster report that it had recently identified the case.

The worker received two doses of an approved COVID-19 vaccine, according to the guidelines, and had completed the series in early January.

The individual traveled to multiple mainland cities about a month later.

Pre-travel testing was performed for the person and a travel companion before returning to Hawaii.

Their positive results were received after they arrived in Hawaii.

Neither of the two developed any symptoms and no transmission to close contacts occurred, the Health Department said.

Officials said laboratory specimens could not be obtained for sequencing, which can identify a variant of the virus.

Health officials have stressed that being vaccinated for COVID-19 does not guarantee that a person will not contract the coronavirus that causes COVID-19 disease. The CDC says the vaccines in use in the United States are “effective at preventing COVID-19 disease, especially severe illness and death.”

However, CDC officials caution that “we’re still learning how effective the vaccines are against variants of the virus that causes COVID-19. Early data show the vaccines may work against some variants but could be less effective against others.

“We’re still learning how well COVID-19 vaccines keep people from spreading the disease.”

They stress that other prevention steps — such as wearing masks, avoiding crowds and practicing social distancing — “help stop the spread of COVID-19, and that these steps are still important, even as vaccines are being distributed.”