JUNEAU, ALASKA -- The state health department Tuesday said upcoming appointments for the single-dose Johnson & Johnson COVID-19 vaccine in Alaska are being cancelled or delayed after federal agencies recommended a "pause" to review reports of rare but potentially dangerous blood clots.

State health officials told reporters the federal recommendation shows that safety checks are working and they hope this bolsters rather than hinders confidence in the vaccine rollout.

Dr. Joe McLaughlin, the state epidemiologist, said people with appointments for the other COVID-19 vaccines authorized for emergency use in the U.S., the two-dose Moderna and Pfizer vaccines, should continue with their appointments.

McLaughlin said the cases involving the Johnson & Johnson vaccine appeared to be "extremely rare," and COVID-19 vaccine safety is "a top priority for all of us, and we take all reports of health problems following COVID-19 vaccination very seriously."

The U.S. Centers for Disease Control and Prevention and Food and Drug Administration said they were investigating six cases of a rare type of blood clot, all involving women. One patient died.

McLaughlin said none of the six cases occurred in Alaska. He said it was unclear how long use of the J&J vaccine would be paused.

More than 6.8 million doses of the J&J vaccine have been given in the U.S.

In Alaska, the state health department said more than 11,000 doses of the J&J vaccine had been administered out of 35,500 doses allocated. That does not include doses allocated to the U.S. Department of Defence or U.S. Department of Veterans Affairs, said Kelsey Pistotnik, a public health advisor to the state immunization program.

State health officials said they have in stock Pfizer and Moderna vaccines that providers could offer instead but acknowledged some people have specifically sought out the J&J vaccine.

Any provider who wants to use Pfizer or Moderna instead would need to let those with appointments know they would be offering a different product than originally advertised, said Tessa Walker Linderman, co-lead of Alaska's COVID-19 Vaccine Task Force.

In Juneau, the city announced a clinic scheduled for Friday would offer the Pfizer vaccine instead of the originally planned J&J vaccine. Robert Barr, emergency operations planning chief for the city, said about 16 people had registered for the initial clinic.

About 28 per cent of Alaska's population is considered fully vaccinated, according to the state health department.