SALEM — The latest forecast suggests that coronavirus infections and hospitalizations in Oregon will continue to decline until Halloween before a new fall wave ensues brought on by waning immunity from current vaccinations.

The new weekly forecast from Oregon Health & Science University acknowledges that the fall wave may be mitigated by updated vaccine boosters. Those single-dose vaccines, which began arriving in Oregon on Thursday, Sept. 1, train the immune system to recognize both the original strain of COVID-19 and the dominant BA.4 and BA.5 subvariants, preventing infection, transmission, serious illness and death.

The Western States Scientific Safety Review Workgroup and the governor approved distribution of the new doses on Sept. 1. The state had preordered more than 75,000 doses and some pharmacies are already booking appointments.

The Moderna booster is authorized for people age 18 and older, while the Pfizer booster can be given to people who are at least 12 years old, according to the Oregon Health Authority.

The agency reported that people can have the Moderna or Pfizer boosters two months after they’ve completed the initial two-dose series or a single dose of the Johnson & Johnson vaccine.

Or, people can take it two months after a monovalent booster of either the Pfizer or Moderna vaccines.

As things stand, the new forecast shows the number of Oregonians hospitalized with COVID-19 will decline by about half from about 268 beds reported Sept. 1 to a low of 125 on Halloween day before heading back upward as infection rates rise anew. A significant share of those hospitalizations are expected to be incidental, among people being treated for other conditions.

The trough in hospitalizations is a little lower than the university forecast Aug. 18.

Community spread of COVID-19 has also continued to decline in Oregon. The Centers for Disease Control and Prevention has listed Union, Wallowa and Baker counties at low levels of community spread.