HONOLULU (HawaiiNewsNow) - The spike in new COVID cases can no longer be blamed on July Fourth gatherings, but is more likely linked to the spread of the highly contagious delta variant, experts said.

University of Hawaii forecast models show cases -- and hospitalizations -- will continue to spike into the fall if the state's vaccination efforts stall.

During the pandemic, a team of scientists from the Hawaii Pandemic Applied Modeling Work Group has been forecasting COVID-19 infections and hospitalizations.

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The latest models show Oahu's cases continue to grow in the coming months -- if current vaccination rates and mandates remain the same.

"We are trying to understand how alarming it can be for Hawaii," said UH mathematics professor Monique Chyba.

Based on models, infections on Oahu are expected to peak in mid-September at 252 cases.

Models show two-thirds would be among unvaccinated people with a third of infections among vaccinated people.

It also shows worst-case scenarios.

If the vaccination rate stops at 70%, Oahu cases reach 391 in mid-November. If the vaccination rate stops at 65%, Oahu cases could reach 687 in mid-November.

"Mathematics does not lie. It does not have a political agenda and I hope that people can understand that," said Chyba.

Scientists are most concerned about hospitalizations.

The forecast predicts 130 people on Oahu could be hospitalized in September. The vast majority would be unvaccinated people while one-fifth would be vaccinated.

"Is there the possibility that you can test positive with the delta variant even after being fully vaccinated? Yes," said Thomas Lee, UH epidemiologist.

But Lee is more worried about unvaccinated people.

"You are very unlikely to be symptomatic or go to the hospital if you are fully vaccinated," said Lee.

"The viral load in a fully vaccinated asymptomatic individual is much lower than an asymptomatic unvaccinated individual," he added.

Compared to last July, infections on Oahu have doubled and are rising faster due to the highly contagious delta variant.

"We are actually seeing this year we are in a worse situation than last year despite having the vaccination," said Chyba.

Experts say what they can't predict is how people will change their behavior or how effective the vaccines will be over time.

The virus is evolving all the time and they're already tracking another mutation called delta plus.

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