The Hawaii Department of Health’s cluster report today focuses on the spread of the coronavirus among Hawaii residents participating in summer volleyball tournaments on the U.S. mainland.

Health officials said exposure to COVID for two clusters likely happened during travel as well as time spent in crowded, poorly ventilated indoor events. Both tournaments were held at indoor stadiums with thousands of attendees, without physical distancing. Also, masks were not required at the practices or tournaments.

One was held in June in Las Vegas, and resulted in a cluster of 16 cases. A total of 48 Hawaii residents attended, and nine tested positive upon their return to Hawaii, including three players. Seven more secondary cases were identified in one household. all of which were unvaccinated.

Three of the of 16 cases, however, were fully vaccinated, and considered breakthrough cases. Of the three breakthrough cases, one was hospitalized, while the other two did not experience any symptoms.

The other tournament involving four teams with teens ages 16 to 18 was held in July in Kansas City, Mo. A total of 58 Hawaii residents attended, and 14 tested positive. Five members of this cluster were fully vaccinated, and considered breakthrough cases; all reported mild systems and none were hospitalized.

DOH recommends that all players, family members, and coaches attending large, mainland events get tested for COVID following their return to Hawaii, regardless of their vaccination status, a negative travel test, or presence of symptoms.

Those who are fully vaccinated do not need to quarantine after a known COVID exposure, but should get tested three to five days afterwards, according to new Centers for Disease Control and Prevention guidelines.

DOH said vaccination against COVID-19 is still the best defense against severe illness, hospitalization, and death.

The report reveals 38 clusters under investigations, more than double the number two weeks ago, and across a broad range of categories — from educational settings to workplaces and social gatherings.

Health officials are currently investigating the following:

>> On Oahu, officials are investigating four restaurant clusters resulting in 35 cases, two social gathering clusters with 34 cases, two clusters from other occupational settings with 31 cases, two clusters in the construction & industrial category with 24 cases, two educational setting clusters with eight cases, a bar/nightclub cluster with five cases, and a shelter cluster with four cases (14 clusters, 141 cases total).

>> On Maui County, officials are investigating three clusters from social gatherings with 23 cases, a cluster from a correctional facility with 18 cases, three clusters at other occupational settings with 17 cases, two educational setting clusters with 17 cases, one shelter cluster with 17 cases, one restaurant cluster with 16 cases, two clusters in travel, lodging & tourism with eight cases, one cluster in a construction & industrial setting with six cases, and one cluster at a food supplier with 5 cases (15 clusters, 127 cases total).

>> On Hawaii County, officials are investigating a cluster at a correctional facility resulting in 291 cases, one at a place of worship with 33 cases, two in the “other” category with 18 cases, one at a restaurant with 17 cases, and two educational setting clusters with 12 cases (seven clusters, 371 cases total).

>> On Kauai County, officials are investigating a cluster at an educational setting with eight cases, and a shelter cluster with six cases (two clusters, 14 cases total).